Saunders Solutions in Veterinary Practice: Small Animal Ophthalmology PDF

1 SAUNDERS SOLUTIONS IN VETERINARY PRACTICE SMALL ANIMAL OPHTHALMOLOGY Fred Nind, BVM&S, MRCVS Sally M. Turner, MA VetMB DVOphthal MRCVS RCVS Specialist in Veterinary Ophthalmology SAUNDERS 2  Front Matt...

1 SAUNDERS SOLUTIONS IN VETERINARY PRACTICE SMALL ANIMAL OPHTHALMOLOGY Fred Nind, BVM&S, MRCVS Sally M. Turner, MA VetMB DVOphthal MRCVS RCVS Specialist in Veterinary Ophthalmology SAUNDERS 2  Front Matter SAUNDERS SOLUTIONS IN VETERINARY PRACTICE SMALL ANIMAL OPHTHALMOLOGY Series Editor: Fred Nind BVM&S, MRCVS Sally M. Turner MA VetMB DVOphthal MRCVS RCVS Specialist in Veterinary Ophthalmology Edinburgh London New York Oxford Philadelphia St Louis Sydney Toronto 2008 Commissioning Editor: Joyce Rodenhuis, Rita Demetriou- Swanwick Development Editor: Sarah Keer-Keer, Louisa Welch Project Manager: Jess Thompson Designer/Text Design: Charles Gray/Keith Kail Illustrations Manager: Merlyn Harvey Illustrator: Deborah Maizels 3  Copyright © 2008, Elsevier Limited. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permissions may be sought directly from Elsevier’s Rights Department: phone: (+1) 215 239 3804 (US) or (+44) 1865 843830 (UK); fax: (+44) 1865 853333; e-mail: [email protected]. You may also complete your request on-line via the Elsevier website at http://www.elsevier.com/permissions. First published 2008 ISBN: 978-0-7020-2872-4 British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging in Publication Data A catalog record for this book is available from the Library of Congress Notice Knowledge and best practice in this field are constantly changing. As new research and experience broaden our knowledge, changes in practice, treatment and drug therapy may become necessary or appropriate. Readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administration, and contraindications. It is the responsibility of the 4 practitioner, relying on their own experience and knowledge of the patient, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the publisher nor the author assumes any liability for any injury and/or damage. To the fullest extent of the law, neither the Publisher nor the Author assumes any liability for any injury and/or damage to persons or property arising out or related to any use of the material contained in this book. Neither the Publisher nor the Author assumes any responsibility for any loss or injury and/or damage to persons or property arising out of or related to any use of the material contained in this book. It is the responsibility of the treating practitioner, relying on independent expertise and knowledge of the patient, to determine the best treatment and method of application for the patient. The Publisher Printed in China. 5  Dedication To Jeff Thank you again for your love and support 6  Introduction Fred Nind, Series Editor Saunders Solutions in Veterinary Practice series is a new range of veterinary textbooks which will grow into a mini library over the next few years, covering all the main disciplines of companion animal practice. Readers should realize that it is not the intention of authors to cover all that is known about each topic. As such the books in the Saunders Series are not standard reference works. Instead they are intended to provide practical information on the more frequently encountered conditions in an easily accessible form based on real life case studies. They cover that range of cases which fall between the boringly routine and the referral. The books will help practitioners with a particular interest in a topic or those preparing for a specialist qualification. The cases are arranged by presenting sign rather than by the underlying pathology as this is how veterinary surgeons will see them in practice. Each case also includes descriptions of underlying pathology and details of the nursing required both in the veterinary clinic and at home. It is hoped that the books will also, therefore, be of interest to veterinary students in the later parts of their course and to veterinary nurses. Continuing professional development (CPD) is mandatory for many veterinarians and a recommended practice for others. The Saunders Series will provide a CPD resource which can be accessed economically, shared with colleagues and used anywhere. They will also provide busy veterinary practitioners with quick access to authoritative information on the diagnosis and treatment of interesting and challenging cases. The robust cover has been made 7 resistant to some of the more gruesome contaminants found in a veterinary clinic because this is where we hope these books will be used. Joyce Rodenhuis and Mary Seager were the inspiration for the Series and both the Series editor and the individual authors are grateful for their foresight in commissioning the Series and their unfailing support and guidance during their production. OPHTHALMOLOGY Ophthalmologic cases can be challenging. The proliferation of veterinary ophthalmology societies and study groups testify to the rapid expansion in the knowledge and skill base in this area. Incorrect or inadequate treatment can compromise what is an important sense for all companion animal species or lead to debilitating pain and discomfort. Indeed, the failure to accurately diagnose some ophthalmic conditions, and then treat them appropriately, can result in loss of the eye, which could have been avoided had the correct approach to the case been followed. Most of the cases discussed can be dealt with in general practice, but where referral to a suitably experienced colleague is recommended, this is mentioned within the text. The book includes a section on the ophthalmic examination – such a fundamental part of the subject that its omission would be negligent! The choice of cases discussed covers selected areas of the subject, particularly common or potentially frustrating cases, as well as the occasional less frequently encountered diseases which should, nonetheless, be recognized by general practitioners. Each section is fully illustrated – ophthalmology is clearly such a visual subject that colour photographs are essential! Several useful appendices are included, covering for example ophthalmic emergencies, conditions which should be checked for in young animals and commonly used pharmacological agents. It is hoped that this book will help 8 practitioners to keep up to date in this discipline, rise to the challenge that eye cases pose and develop confidence in dealing with ophthalmologic cases. 9  Table of Contents Front Matter Copyright Dedication Introduction Chapter 1: The ophthalmic examination Chapter 2: Laboratory investigation Part 1: EYELIDS Chapter 3: Eyelids – introduction Chapter 4: Blepharitis Chapter 5: Complicated entropion Chapter 6: Large eyelid mass Chapter 7: Eyelash problems – distichiasis and ectopic cilia Chapter 8: Prolapsed nictitans gland Part 2: CONJUNCTIVA Chapter 9: Conjunctiva – introduction Chapter 10: Acute conjunctivitis in dogs Chapter 11: Feline conjunctivitis Chapter 12: Medial canthal pocket syndrome Chapter 13: Rabbit conjunctivitis Chapter 14: Aberrant conjunctival overgrowth in rabbits Part 3: NASOLACRIMAL SYSTEM Chapter 15: Nasolacrimal system – introduction 10  Chapter 16: Complicated keratoconjunctivitis sicca Chapter 17: Chronic epiphora Chapter 18: Dacryocystitis – chronic purulent conjunctivitis Chapter 19: Rabbit dacryocystitis Part 4: CORNEA Chapter 20: Cornea – introduction Chapter 21: Recurrent epithelial erosion Chapter 22: Deep corneal ulcer Chapter 23: Complicated corneal ulcer Chapter 24: Puppy scratched by cat Chapter 25: Corneal foreign body Chapter 26: Corneal endothelial dystrophy Chapter 27: Proliferative (eosinophilic) keratoconjunctivitis Chapter 28: Brachycephalic pigmentary keratitis Chapter 29: Chronic superficial keratitis Chapter 30: Feline corneal sequestrum Chapter 31: Chronic feline keratitis Part 5: UVEA Chapter 32: Uveal tract – introduction Chapter 33: Canine uveitis Chapter 34: Feline uveitis Chapter 35: Rabbit uveitis Chapter 36: Hyphaema Chapter 37: Canine intraocular neoplasia Chapter 38: Leishmaniasis 11 Part 6: LENS Chapter 39: Lens – introduction Chapter 40: Diabetic cataract in a dog Chapter 41: Cataract in a young dog Chapter 42: Canine lens luxation Part 7: GLAUCOMA Chapter 43: Glaucoma – introduction Chapter 44: Primary canine glaucoma Chapter 45: Secondary canine glaucoma Chapter 46: Feline glaucoma Part 8: FUNDUS Chapter 47: Fundus – introduction Chapter 48: Generalized progressive retinal atrophy Chapter 49: Retinal detachment Chapter 50: Sudden acquired retinal degeneration Chapter 51: Hypertensive retinopathy Part 9: ORBIT AND GLOBE Chapter 52: Orbit and globe – introduction Chapter 53: Exophthalmos Chapter 54: Enophthalmos Chapter 55: Proptosis Chapter 56: Limbal melanoma Chapter 57: Episcleritis MCQs MCQs – Answers 12 APPENDIX 1: Equipment and instruments required for ophthalmic surgery in general practice APPENDIX 2: Ocular pharmacology APPENDIX 3: Ocular emergencies and what to refer APPENDIX 4: Congenital ocular problems – what to check for at the first vaccination APPENDIX 5: Differential diagnosis according to the presenting signs Further reading Index 13  1 The ophthalmic examination A full ophthalmic examination should be performed on all animals presenting with an ocular complaint. To perform this properly it is important to have a standard approach to all patients together with appropriate facilities and equipment. The basic parts of the ophthalmic examination are: History taking Hands-off examination Hands-on examination – Schirmer tear test readings – Vision testing and neurological testing – Ophthalmoscopy. Further tests include: Ophthalmic dyes Nasolacrimal duct investigation Tonometry Laboratory investigation. Table 1.1 Facilities and equipment required for the ophthalmic examination General practice Those with an interest in ophthalmology Room capable of being fully darkened All items listed left plus: Table of adjustable height Slit lamp biomicrosope Pen torch Finhoff transilluminator Direct ophthalmoscope Indirect ophthalmoscope Magnifying lens Goniolens Magnifying loupe Tonopen or Tonovet tonometer Tonometer (Shiotz) Disposable items required for ophthalmic examination are: 14  Schirmer tear test papers Fluorescein paper test strips Rose Bengal dye (for specialty ophthalmology practice) Cotton wool and gauze swabs Tropicamide (Mydriacyl 1% Alcon) Topical anaesthetic (proxymetacaine) Sterile saline Lacrimal cannulae Bacterial swabs and transport media Slides and laboratory equipment. HISTORY History taking can be divided into general history and that specifically pertaining to the eyes. A general history should consider the following points: Genetics: As breed pedigree dogs and cats can suffer from inherited eye diseases, the breed is of importance. Even in crossbred dogs the general type of dog might be relevant – for example, terriers are prone to lens luxation which is seen in pedigree wire haired fox terriers and miniature bull terriers among others, but is common in all types of Jack Russell from the pedigree Parson terrier to the general terrier type. In cats, corneal sequestrum is a common condition in Persians and Burmese while retinal degeneration is recognized in Siamese and Abyssinian breeds. Clearly we should not assume that just because a patient is a particular breed it will definitely be suffering from a certain condition – but breed-related diseases are frequently encountered in veterinary ophthalmology. Age: This is always a factor to be considered. Conditions such as entropion and prolapse of the nictitans gland (cherry eye) are common in young animals (3–12 months) while neoplasia is more common in older patients. Congenital problems such as cataract and collie eye anomaly should be considered when patients come in for 15 their initial vaccinations (see Appendix 4). Sex: Although of less importance with regard to ophthalmology than for some other disciplines, the sex of the patient might have some influence on its ocular disease. For example, young male dogs are more prone to entropion while keratoconjunctivitis sicca is seen in neutered females more commonly than entire males. General health: Many ocular conditions can be manifestations of systemic disease and questions related to appetite, general demeanour and concurrent illness are extremely important. Patients might be presented with sudden blindness as the owner’s complaint, which turns out to be due to diabetes mellitus and the owner has failed to appreciate that the polydipsia, weight loss and so on were actually due to a serious medical condition. Medications administered: Previous or ongoing medication may be the cause of some ophthalmic conditions. An example is the dog with colitis which is treated with sulfasalazine (Salazopyrin) and develops an acute, severe bilateral keratoconjunctivitis sicca. Some ophthalmic drugs can cause a localized hypersensitivity which exacerbates the ocular disease. Owners are notorious for using left- over medication from a previous problem – which might not even have been for the pet! Such actions can be deleterious to the patient. Presence of other pets in the house: This is particularly relevant when considering infectious diseases such as feline herpes virus where repeated infection can be a problem. If the owner has more than one pet it is important to find out if others are affected. The presence of a new puppy in a home with a cat might be relevant if the puppy is brought to the surgery with an acutely painful eye – it is quite likely that the cat has scratched it! Source of the pet: Cats from rescue centres and/or breeders may have pre-existing diseases such as herpes or Chlamydophila infections, while dogs from puppy farms may be prone to inherited ocular disease since unscrupulous breeders pay no attention to such things. 16  Travel history: This is becoming more and more relevant in the UK since the introduction of the Pets Passports schemes but is relevant in all countries. Several Mediterranean diseases such as leishmania and ehrlichia can have ocular involvement. Once a thorough general history has been taken we can move on to the more specific ophthalmic history. This will include asking the owners the following questions: What was the first thing the owner noticed wrong with the eye(s)? Were they concerned about discharge, pain, redness or other change in colour, an alteration in appearance of the eye (e.g. bulging or sunken) or perhaps they noted a decrease in vision. When did they notice something wrong? The time span of the disease is relevant – some owners will bring a pet along to the surgery immediately while there are those owners who leave the pet for weeks or even months before presenting it. Progression of the problem? Has the problem got worse, better or stayed the same since it was first noticed? Has it been present continuously or has it been intermittent? If the latter, has the owner noticed any ‘trigger factor’ which brought on a return of the symptoms? For example, did the atopic Labrador always have itchy eyes when he returned from a walk through certain fields? (This could suggest an allergic component.) Is the problem unilateral or bilateral? As mentioned in the general history taking, systemic disease may be the underlying problem and this is much more likely with bilateral conditions. With infectious disease we might also expect a bilateral presentation although it is not unusual for one eye to be affected before the other – Chlamydophila in cats is an example where a delay of a few days can be seen before the second eye develops symptoms. Treatment – has the owner given any medication? If so, what, and was it beneficial or detrimental? Previous ocular history? It is important to establish whether the pet 17 has had any ocular problem in the past – and, if so, was the presentation the same and was it the same eye which was affected? Also, response to treatment given previously is relevant. THE OPHTHALMIC EXAMINATION Hands-off examination While the history is being taken the patient should be observed. Dogs are allowed to wander off the lead and investigate the consulting room while cats are encouraged out of their baskets and then watched from a distance. It is important to look at the behaviour of the pet, along with the gross appearance of the eyes and face. Signs of ocular discomfort – blepharospasm, increased lacrimation or other discharge, symmetry of the eyes and face – sunken or small eyes, enlargement of the globe, periorbital swellings or squints for example. Clues might inform us that the animal has been rubbing – periorbital hair loss and erythema or saliva staining on the front legs where the animal licks then rubs the face might be evidence of self-trauma. Basic assessment of the visual ability of the patient can be undertaken at this time – blind animals will often stay close to the owner and not move around the room, while if they do move they are often very cautious, sniffing the environment and exhibiting a high stepping gait. Hands-on examination The first part of the hands-on examination takes place in a well-lit room. The patient should be gently restrained – one hand under the chin and the other behind the back of the head is usually sufficient. A trained nurse is invaluable during ocular examinations – most owners are not very good at restraining their pets in general, and when you are very close to the biting end it is particularly important that the patient is properly held by a confident adult! 18  A close inspection of the gross appearance of the eyes and face is performed with illumination such as a pen torch. Particular things to consider include the presence of any ocular discharge – the nature of it, whether unilateral or bilateral and the amount of it. Some dogs commonly have a small amount of mucoid discharge at the medial canthus, especially those with doliocephalic conformation such as Dobermanns, and it can be considered a normal finding in such animals. The size of both eyes should be compared – they should be symmetrical but if one is larger than the other it is necessary to establish whether one is enlarged (hydrophthalmic) or if one is shrunken (microphthalmic). In addition to size, the actual position of the eyes should be noted – looking from above the patient directly down on the head can assist in establishing the presence of exophthalmos, enophthalmos or strabismus. General head symmetry and the presence of periorbital swellings should also be noted. It might be necessary to take samples for laboratory analysis at this stage if indicated. Swabs for bacterial culture and isolation should be taken before any discharges are cleaned away. Schirmer tear test readings Schirmer tear test readings should be taken before the eyes are cleaned or handled further. Commercial tear testing strips are used (colour bar calibrated strips are the easiest to use and are available from Schering-Plough). The strips come in sterile plastic wallets. The strips should be bent at the notch while still in their plastic wallet (to prevent sweat and grease from hands interfering with the readings). The packet is opened and each test paper is held at the distal end. The shorter piece is placed in the ventral conjunctival sac half to two-thirds along from the medial canthus (i.e. out of the way of the third eyelid) (Figure 1.1). The strip is left in position for 1 minute before removing it and immediately reading the level of wetting on the scale (see Table 1.2). It is easier to hold the patient’s eye closed to prevent the strip from falling out prematurely. Topical 19 anaesthetics are not used prior to measurement. Figure 1.1 Schirmer tear test in a cat showing placement of paper strip. Table 1.2 Schirmer tear test readings in dogs and cats Dog Cat Normal 15–25 mm/min Readings variable Borderline 10–15 mm/min and often lower than in the dog, especially in stressed cats Keratoconjunctivitis sicca 2 mm generate a response in approximately 80% of cases. Although twice daily administration is the recommended dose, it is sensible to increase this to three or even four times daily in cases which have previously responded then deteriorated and in neglected cases. Clients should be reminded not to apply too much – the size of a large grain of rice is sufficient. Despite the high cost of the drug they tend to apply too 214 much, often with the false assumption that more will increase efficacy. More frequent dosing might, but more ointment will not! Also remember that excessive ciclosporin accumulation on the lid margins can trigger a hypersensitivity reaction and thus blepharitis – if this is present it is important to establish exactly how the owner applies the medication. In addition to controlling infection, and trying to stimulate increased tear production, more frequent application of topical lubricants is indicated. There are many different formulations available over the counter for people suffering from dry eyes and some people benefit from one type of tear substitute over another. The same is true for our patients and changing lubricant can help. In general, the longer-acting and viscous agents, such as carbomer gel, hydroxypropyl methylcellulose and hylan, are more effective than the traditional polyvinyl alcohol drops. Unfortunately they tend to be more expensive! Ointments such as soft white paraffin are useful at night or if owners are unable to medicate sufficiently frequently during the day. If, after 4 weeks of increased frequency of application, there is still no improvement in tear production, then it is acceptable to compound a stronger formulation of ciclosporin under the Cascade system. Traditionally, a 2% solution is made by diluting the oral (not intravenous) human formulation in inert corn oil. This is applied two to three times daily and can significantly improve Schirmer tear test readings after 4 weeks. Owners must be made aware that this is an off-licence use of the drug and appropriate forms must be signed. Another recently discovered tear stimulant, tacrolimus, is also effective in poorly responsive cases but is not licensed at all and thus its use is probably best advised only by specialists. The use of topical anti-inflammatory agents is controversial with refractory KCS. Certainly topical steroids do reduce the conjunctival 215 hyperaemia and hyperplasia along with the corneal vascularization (which subsequently slows the deposition of pigment on the cornea since the blood vessels are the source of the pigment). However, the risk of ulceration is high anyway, and could be exacerbated by long- term topical steroids. The change in commensal bacteria induced by topical steroids can also predispose to more pathogenic bacterial infections. However, the potential benefits can outweigh the potential complications in some patients and their judicious use is sometimes necessary. If any blepharitis is present, as is often the case with refractory KCS (especially in cocker spaniels!), then systemic antibiotics are indicated. A 2–3 week course of a cephalosporin is usually necessary. If the eyelid margins are very inflamed or ulcerated from self-trauma, a short course of oral corticosteroids (at an anti- inflammatory not immunosuppressive dose) may be beneficial but they should not be used in conjunction with topical steroids due to the high risk of ulceration. TREATMENT OPTIONS – SURGICAL If severe corneal ulceration is present, surgical intervention using a pedicle conjunctival graft is indicated as discussed in Case example 23.1 on complicated ulcers and also mentioned in Case example 16.2 below. CASE EXAMPLE 16.2 Patient details: Cavalier King Charles spaniel, 11 years old, female (neutered) In cases with marked pigmentary keratitis, such that vision is impaired, superficial keratectomy to remove the pigmented corneal deposits has been advocated. However, it is not recommended in poorly controlled cases of KCS. Although the surgery is relatively 216 straightforward, removing just the corneal epithelium and anterior stroma, the success is usually short lived. A large, albeit superficial, corneal ulcer is produced by the surgery and its healing is frequently not without complications. Corneal melting, infection, severe vascularization and scarring, and rapid repigmentation all occur. Even in cases of pigmentary keratitis due to other causes (e.g. brachycephalic dogs with lagophthalmos), this surgery is rarely advised, and treatment options aim to reduce the trigger to the pigment deposition rather than removing it after it has formed. Continued use of ciclosporin, even in the absence of increased tear production, can help to reduce the pigment via its anti-inflammatory action. The main surgical option for non-responsive KCS remains parotid duct transposition. It is interesting to note that the frequency with which this surgery is performed in American Veterinary Colleges has dropped from more than 15% of KCS cases in the late 1970s and early 1980s to less than 2.5% in the late 1990s according to the American Veterinary Medical Data Program. This is mainly due to the advent of ciclosporin and increased earlier recognition of the disease, and clearly is good news for our patients. However, parotid duct transposition surgery is still indicated in cases with minimal tear production, severe corneal ulceration (as well as surgery for the ulcer) and where frequent medical treatment is not feasible due to owner restraints or a lack of patient compliance. The surgery can be performed in general practice, but since it is no longer routinely required it might be best to consider referral to a specialist who has the necessary expertise and still undertakes this microsurgical procedure with some frequency! It is essential to check that the patient produces saliva normally prior to considering surgery – xerostomia (dry mouth) occasionally accompanies KCS. Placing a bitter substance on the tongue, such as lemon juice or a drop of atropine, should result in copious salivation 217 and on careful inspection drops of saliva can be seen issuing from the parotid duct papilla just above the carnassial tooth on the buccal mucosa. If this does not occur, the patient will not benefit from parotid duct transposition surgery. Owners need to be carefully informed of the reason for choosing the surgery and the potential complications which can occur. It is a salvage procedure for the eyes and although it is often very successful and of great benefit to the patient, it can be a bit of a poisoned chalice on occasion. Normally the surgery is successful in that the eye becomes wet with saliva almost immediately. However, saliva contains a much higher mineral concentration than tears, and salty deposits can accumulate both on the eyelids and the cornea itself. These are often benign but some patients become uncomfortable and require removal either with EDTA drops or even superficial keratectomy. Lubricants to soothe the irritation can also help (soft liquid paraffin ointment for example). Bacterial infections can occur more commonly than in normal eyes – the usual conjunctival flora is changed considerably following surgery – and owners should be made aware that if there is any change in the nature of the discharge or patient comfort they should present the patient at the surgery. Another potential problem following parotid duct transposition is epiphora – the degree of salivation into the eye cannot be controlled and in some dogs is excessive such that they have permanent tear overflow and resultant moist dermatitis on the face. This can be a particular problem in the ‘slobbery’ breeds such as Neapolitan mastiffs, such that surgery might even be contraindicated. Many dogs will ‘cry’ when fed or if food is being prepared, but providing this is not excessive it is an acceptable alternative to end-stage KCS. 218 Figure 16.5 Decision-making tree – KCS. PROGNOSIS The prognosis for complicated KCS is somewhat guarded in a number of cases. If severe ulceration has developed, then both conjunctival grafting and parotid duct transposition might be indicated (sometimes at the same time) but even after this the eye will never be ‘normal’. Occasionally enucleation is necessary. With chronic pigmentation vision can be impaired and even following parotid duct transposition complications with irritation and blepharitis from mineral deposition are not uncommon. Thus early diagnosis and regular monitoring, with good owner and patient compliance, are required to prevent such complications. 219 Figure 16.6 Decision-making tree – severe KCS. CASE EXAMPLE 16.1 Patient details: Miniature long haired dachshund, 13 years old, male (neutered) PRESENTATION AND HISTORY The patient had a long history of keratoconjunctivitis sicca affecting both eyes, which had initially been diagnosed 3 years previously. It had been well controlled on twice daily ciclosporin and carbomer gel, and once daily soft liquid paraffin ointment at night. Schirmer tear test had been between 8 and 14 mm in each eye. However, 2 weeks before presentation 220  the left eye started to discharge more, and the dog was unable to open its eye in the morning. The owner increased the frequency of carbomer gel to four times daily but little improvement occurred and so she presented the dog. He was also hypothyroid but this was well controlled with levothyroxine sodium. CLINICAL SIGNS General clinical examination was unremarkable apart from a slightly dry, scurfy coat. On ophthalmic examination a sticky mucopurulent discharge was present in the left eye, adherent to the cornea (Figure 16.7). Severe superficial corneal vascularization and pigment deposition were also noted. Schirmer tear test readings were 3 mm/min in the left eye and 11 mm/min in the right. Menace responses and pupillary light reflexes were normal and intraocular examination, although limited, showed no gross abnormalities. A swab was taken from the discharge before it was cleaned away and the cornea stained with fluorescein. This revealed no ulceration. Figure 16.7 Chronic KCS in a 13-year-old dachshund showing discharge adherent to cornea, pigmentation and marked superficial corneal vascularization. Note also the trichiasis dorsolaterally. WORK-UP 221 The swab was submitted for bacterial culture and sensitivity, and showed a profuse growth of coagulase-positive Staphylococcus spp. with moderate resistance to fusidic acid and ciprofloxacin, although it was sensitive to chloramphenicol. Thyroid function was checked and found to be satisfactory. TREATMENT AND OUTCOME The ciclosporin was increased to four times daily in the left eye, and chloramphenicol drops were started at the same frequency. Topical carbomer gel was applied every 3 hours during the day and the soft white paraffin continued at night. After a week the discharge had reduced but tear production was still only 5 mm/min and significant conjunctival hyperaemia remained. It was decided that anti- inflammatory medication was required, but the use of topical steroids was not advised given the risk of ulceration and so prednisolone was started at 0.5 mg/kg/day for 5 days then every other day for 10 days. The topical medication continued. The eye improved well, with Schirmer tear test readings of 10 mm in the left and 12 mm in the right after 3 weeks. The treatment was then continued with ciclosporin three times in the left (still twice in the right) and lubricants four times daily. After another month tear production was 14 mm in the left and the ciclosporin was reduced to twice daily. This example illustrates that controlled cases of keratoconjunctivitis sicca can wax and wane such that the medication needs to be adjusted. The dog clearly developed a bacterial infection but it is difficult to know if this was the reason for the reduction in tear production or a result of it. Tear production remained low despite apparently controlling the infection, which suggested some lacrimal gland adenitis. The systemic steroids appeared to settle this and tear production returned to the pre- infection levels. 222  PRESENTATION AND HISTORY The dog had a 1-year history of bilateral KCS which was controlled on the standard medication of twice daily ciclosporin only. Tear production had increased from 8 mm/min to 16 mm/min (similar in both eyes) and no problems were reported. However, suddenly the right eye started to discharge excessively and the dog cried out when the owner tried to clean the eye. They started using some chloramphenicol drops twice daily which they had in the house. They presented the dog 5 days later. CLINICAL SIGNS The dog was slightly depressed but otherwise clinically unremarkable. The right eye was closed and the dog shied away and cried when attempts were made to examine it. A copious mucopurulent ocular discharge was present. Schirmer tear test readings were 8 mm/min in the right and 4 mm/min in the left. The latter had mild corneal vascularization and conjunctival hyperplasia typical of chronic KCS. After gently cleaning the right eye the severe corneal pathology became apparent. Marked corneal oedema and vascularization were present with what appeared to be intrastromal haemorrhage. A ventrolateral ruptured corneal ulcer was present, along with a deep ulcer more medially which was obscured by the third eyelid (Figure 16.8). A dazzle response was present but no menace response and a pupillary light reflex could not be assessed, although there was a consensual constriction of the left pupil when light was shone in the right. 223 Figure 16.8 Eleven-year-old CKCS with chronic KCS and acute ulceration. Note corneal oedema, vascularization and ruptured pinpoint corneal ulcer (the bubble of aqueous can be seen in the defect). Copious mucopurulent discharge with some adherent to the cornea is typical of severe KCS. WORK-UP A swab was taken from the discharge but no significant growth was detected. It is difficult to know if this was as a result of the previous usage of chloramphenicol drops, although twice daily is a suboptimal level to achieve the bacteriostatic effect. The owners were given the option of attempting to salvage the eye or enucleation and opted for the former, and referral for this was arranged. Parotid duct transposition was discussed but the owners were reluctant to have this procedure as well. Pre-anaesthetic blood tests were unremarkable. TREATMENT Under general anaesthesia the corneal ulcers were repaired using a long conjunctival pedicle graft sutured into the two ulcers (Figure 16.9). Postoperative medication was intensive (see Table 16.2) and continued for 2 weeks before reducing to just ciclosporin three times daily and frequent lubrication. Ciclosporin was increased to three 224 times daily in the left at the time of surgery since tear production was also reduced in this eye. Figure 16.9 Same eye as Figure 16.6, 2 weeks after conjunctival graft. Table 16.2 Postoperative medical treatment for Case example 16.2 Drug Frequency Reason Ciclosporin 4× Try to stimulate increased tearing Ciprofloxacin 6× Treat any infection (in spite of non-diagnostic swab) Tropicamide 3× Mydriasis to reduce reflex uveitis Carbomer gel 6× Topical lubrication Cefalexin 125 mg twice daily Reduce risk of secondary infection Carprofen 20 mg twice daily Analgesia and anti-inflammatory OUTCOME The dog did very well. Four weeks later the graft was incorporated into the cornea and the oedema and vascularization had reduced dramatically. Vision was good. The discharge was also minimal and tear production was back to 10 mm in the right and 8 mm in the left. The dog was continued on ciclosporin three times daily for another 2 months, at which time tear production was 13 mm in the right and 12 mm in the left, and it was reduced to twice daily again. 225  This case illustrates the sudden deterioration which occurs if ulceration develops. The dog could easily have lost the eye. If tear production had not improved again then parotid duct transposition would have been advised. The owners are aware that the left eye could ulcerate and check the dog very carefully. 226  17 Chronic epiphora INITIAL PRESENTATION Discharge PRESENTING SIGNS Epiphora is defined as tear overflow and thus these patients present with wet eyes! The discharge is typically serous in nature and can be unilateral or bilateral. It can be congenital (although the wetness does not often manifest until the animal is over 3–4 months of age) or acquired (e.g. following dacryocystitis or feline herpes virus infection). In most instances the patient is not uncomfortable but the owner is concerned about the wetness or the unsightly staining it causes (especially in pale coloured animals). Sometimes owners will also complain about the smell from the face. CASE HISTORY With congenital problems the owner may have noticed that the puppy had wet eyes right from when they first brought it home from the breeder. They might even have been made aware of the wetness by the breeder (who might have said that the puppy had ‘a bit of a cold’ or had been scratched by one of its littermates). However, the owners might not have been aware of any abnormalities until the puppy was 3–4 months old (or even older) when the epiphora and tear staining became more obvious with the growth of the animal. Sometimes the increased wetness is blamed on the puppy teething but it continues well beyond the full eruption of its adult teeth. The classic patient is the young miniature poodle with bilateral tear 227 staining. With acquired cases the patient is usually older (perhaps with the exception of post-feline herpes virus infection in kittens). Acquired cases normally would have a history of a previous ocular problem – an infection or injury for example – which resolved with treatment but the pet was left with chronic tear overflow. CLINICAL EXAMINATION General clinical examination is typically unremarkable. On ophthalmic examination the obvious abnormality is a wet face – tear overflow from the medial canthus runs down the side of the nose (Figure 17.1). Often there is dark staining (as the presumed lactoferrin-type pigments in tears react with the atmosphere), and some localized skin inflammation and moist dermatitis can be present. It is essential to determine whether the tear overflow is purely due to poor drainage (i.e. epiphora) or to increased lacrimation. Sometimes a combination of both can be present. However, if Schirmer tear test readings are normal and there is no evidence of ocular discomfort, then epiphora can usually be assumed. Figure 17.1 Severe epiphora in a 6-month-old Cavalier King Charles spaniel (CKCS). 228  Careful examination with magnification and a good light source are required to evaluate potential causes for the epiphora. The nasolacrimal punctae should be evaluated for presence, size and position. Any medial entropion should be assessed together with lid apposition – some toy breeds have very tight skin–globe apposition which functionally reduces drainage. The caruncles in the medial canthi should be examined to see if any hairs are present on them which could be wicking tears away from the punctae and down the face. Other facial hair can contact the tear film and cause wicking as well – the fine curling fur of poodles is an important contributor to tear overflow. Examination for conditions which could cause irritation and increase tear production slightly should be undertaken. Thus the presence of nasal folds rubbing on the cornea or conjunctiva, distichia or ectopic cilia, overt entropion or corneal ulcers should be noted (Figure 17.2). In most cases of pure epiphora these latter abnormalities are not present and the rest of the ophthalmic examination is normal. Figure 17.2 Epiphora and increased lacrimation in a young English bulldog. In addition to the tear staining at the medial canthus this dog is wet around the lateral canthus (unlike Figure 17.1) and some lower lid entropion is present causing increased tear production rather than the dog 229 just having poor drainage. Schirmer tear test readings would be high in this dog, but normal in the CKCS in Figure 17.1. DIFFERENTIAL DIAGNOSES Epiphora: – Imperforate punctae – Micropunctae – Misplaced punctae – Medial entropion – Caruncular trichiasis – Tight lid–globe apposition Increased lacrimation: – Entropion – Distichiasis – Ectopic cilia – Corneal ulceration – Nasal fold trichiasis – Intraocular pain CASE WORK-UP The diagnosis should be reached from the ophthalmic examination since the reasons for poor drainage are usually noted on careful inspection of the medial canthal area in particular. Nasolacrimal flushing should be attempted. In the case of imperforate or micropunctae this might not be possible, although normally the upper punctum is of sufficient size for cannulation with a small nasolacrimal cannula (frequently only the lower one is imperforate). Gentle pressure on the syringe attached to the cannula (filled with sterile saline) will result in a small bleb of conjunctiva over the location of the ventral canaliculus pointing to the location for the punctum. This confirms the diagnosis of imperforate punctum and surgery can be performed (see below). 230  If the punctae are of normal size and nasolacrimal flushes are successful, then attention should be focused on tear dynamics and which of the anatomical abnormalities are most important regarding tear overflow such that the appropriate surgery can be performed as detailed in the following sections. NURSING ASPECTS No specific nursing instructions, other than the application of medication as required and bathing the discharge, are necessary. EPIDEMIOLOGY Once again, as is often the case for ophthalmic conditions, the selective breeding of pedigree dogs has led to the clinical problems encountered. Imperforate or micropunctae can occur in any breed, but golden retrievers and cocker spaniels (both English and American) are certainly over-represented, together perhaps with the Cavalier King Charles spaniel, miniature and toy poodle, Samoyed and Bedlington terrier. The tear overflow syndrome seen in the miniature and toy poodle, Maltese terrier and so on is partly due to the head shape and ocular appearance of these dogs which has been specifically chosen by breeders. The small, tight eyelids can lead to medial entropion and physical closure of the punctae which are frequently already small. Unfortunately, the same problems are now seen in brachycephalic cats as well, where selection for the short nose and prominent eyes has led to medial entropion, tight medial lid–globe apposition and trichiasis in exactly the same way as in some dogs. Since in many patients the epiphora does not cause any clinical problem to the animal, and is therefore purely cosmetic, breeders do not see that this is still an abnormality which further selective breeding could reduce significantly. 231  CLINICAL TIPS Determine whether epiphora (STT normal) or increased lacrimation (STT high) is present Look carefully at where the wetness actually is (compare Figures 17.1 and 17.2) Apply fluorescein and see if drainage to nose/oropharynx occurs and watch where the dye goes (e.g. directly over the face on application) Check patency of nasolacrimal system Look carefully at the medial canthal area Rule out causes of ocular pain TREATMENT OPTIONS – MEDICAL In some patients minimal intervention is required. If the epiphora is not excessive, and no moist dermatitis is present, then all that is necessary is regular wiping of the discharge and drying the area. Sometimes the application of a bland ophthalmic lubricant ointment will both guide any hairs away from the canthal area such that the trichiasis is reduced, and will provide a barrier to the tears scalding the delicate skin in the area. Some owners are concerned about the unsightly appearance of the tear staining together with the smell it creates. Systemic antibiotics such as oxytetracycline, doxycycline and metronidazole have been used orally for 2–3 weeks and certainly reduce the tear staining and smell (without lowering Schirmer tear test readings). However, the discoloration returns as soon as they are stopped and clearly they are not a long-term solution. TREATMENT OPTIONS – SURGICAL Surgical correction of imperforate or micropunctae is normally straightforward and successful. Complicated cases, where not only is the punctum absent but the canaliculus has also failed to form 232 properly, are thankfully rare. Under general anaesthesia, ideally with some form of magnification, the upper punctum is cannulated and sterile saline gently injected to delineate the location of the lower punctum – seen as a raised bleb of conjunctiva (Figure 17.3). If the upper punctum is small or difficult to locate, a Nettleship’s dilator, a fine pencil-like instrument, can be gently slid along the inner aspect of the upper lid towards the canthus which will catch on the opening of the punctum and thus can be introduced to slightly stretch it, making cannulation easier. Figure 17.3 Surgery to create a punctum where the lower one is imperforate: (a) cannulate upper punctum then gently inject saline 233  (b) locate ‘bleb’ of conjunctiva over canaliculus, grasp it with fine forceps and cut out the conjunctiva overlying it. Once the bleb is identified the conjunctiva overlying it is removed – a triangular piece is normally excised and the correct location of the punctum is revealed as saline flows though. Once the newly created punctum has been tidied it should be cannulated and drainage to the nose/oropharynx established by flushing with sterile saline. Postoperatively topical mediation with an antibiotic/steroid combination is normally prescribed – the corticosteroid will both reduce any post-surgical inflammation and slow healing such that the punctum remains patent. Owners can be directed to gently massage the medial canthal area after the application of drops or ointment, which again will reduce the risk of the conjunctiva sealing the opening. The success rate following opening or enlarging the punctae is normally good – the epiphora decreases within a couple of weeks. It is uncommon for the punctum to seal over again providing it has been created in the correct place! In the few instances where it does seal over, a second procedure is required and it is prudent to place an indwelling cannula for 2–3 weeks while maintaining the topical medication as above. If the nasolacrimal punctae are present and of normal size, but misplaced (normally more lateral than usual), they can be repositioned by microsurgical techniques which require referral to a suitably qualified colleague. Medial entropion and caruncular trichiasis can be addressed in general practice providing some magnification is available. Surgery at this location is more complicated than laterally due to the tight medial canthal ligament making tissue manipulation more difficult, together with the less easy access to the surgical field. However, a simple Hotz-Celsus procedure along the ventromedial lid can be undertaken. Often the piece of skin removed needs to be almost 234 triangular in shape, with the point of the triangle opposite the punctum, rather than the more usual ellipse (Figure 17.4). Sutures should be fine and soft – 6/0 polyglactin 910 is commonly utilized. If the caruncle is to be surgically removed, it is vital that the nasolacrimal punctae and canaliculi are not damaged. Catheterization of them with coloured nylon will assist in their delineation such that they are not inadvertently lacerated. The canaliculi pass quite superficially and careless surgery can easily damage them. Thus, although the procedure of cutting out the caruncles, including the hair follicles, seems very straightforward, one must be aware of the potential complications and referral should be considered, particularly if good magnification is not available. Figure 17.4 Modified Hotz-Celsus procedure for medial canthal entropion: 235  (a) skin at medial canthus is turned inwards closing punctum and allowing hairs to rub on cornea (b) triangle-shaped piece of skin is removed to return the lid to its normal position. An alternative to surgical excision of the caruncular trichiasis is cryosurgery. Nitrous oxide and liquid nitrogen systems are both suitable. A small probe is applied directly to the caruncle and a double freeze–thaw cycle is employed. Postoperative swelling is to be expected – a topical antibiotic/steroid ointment is necessary for 14 days. The area will depigment and this can worry some owners. If there is no entropion present and the punctae are normal, such that it is only the caruncular trichiasis which needs addressing, then cryosurgery is a reasonable option; however, if sharp surgery is also required it seems sensible to address the caruncular problem via this route as well. Acquired lesions (e.g. following trauma) are more complicated to manage and referral should be considered – particularly if lacerations to the canaliculi or duct have been incurred. PROGNOSIS The prognosis obviously depends on which of the various causes for epiphora are present on a patient-to-patient basis – for example, a simple imperforate punctum in a golden retriever carries a very good prognosis. A combination of medial entropion, tight lid–globe apposition and caruncular trichiasis in a miniature poodle carries only a fair prognosis since although the situation can be improved with surgery the tear dynamics will never be normal and some epiphora is likely to be permanent. However, since this is often cosmetic, with owner education the final outcome is often satisfactory. 236 Figure 17.5 Decision-making tree – epiphora. CASE EXAMPLE 17.1 Patient details: Cavalier King Charles spaniel, 6 months old, male PRESENTATION AND HISTORY The dog was presented with wet eyes and a smell from the face. This had been present since the owner acquired the puppy at 3 months and was getting worse. The dog showed no signs of discomfort and the eyes were not red. 237 CLINICAL SIGNS On ophthalmic examination marked epiphora and tear staining were present bilaterally (see Figure 17.1). No conjunctival hyperaemia or blepharospasm were present and lid alignment was good. Schirmer tear test readings were 21 mm bilaterally, considered normal. No corneal ulceration was present. Gentle eversion of the lower eyelid medially revealed no nasolacrimal punctum ventrally in either eye, although the upper ones were visible (Figure 17.6). Intraocular examination revealed abnormalities on fundus examination – several dark vermiform streaks were present in the tapetal fundus of both eyes consistent with multifocal retinal dysplasia (Figure 17.7). Vision was unaffected. This condition was unrelated to the epiphora but is an inherited condition in the breed and some dogs can be more severely affected with areas of retinal detachment for example. Figure 17.6 Same dog as in Figure 17.1 showing the absence of a ventral nasolacrimal punctum. 238 Figure 17.7 Fundus examination of 6-month-old CKCS showing dark vermiform streaks of multifocal retinal dysplasia in the tapetal fundus. Vision was unaffected. WORK-UP Under topical anaesthesia the upper nasolacrimal punctum was cannulated and saline injected. This appeared at the ipsilateral nostril but none appeared in the eye, confirming an imperforate lower punctum. Close inspection of the lower eyelid at the medial canthus revealed a small bleb of conjunctiva when saline was flushed into the upper punctum. Both eyes were similar. Surgery was advised. TREATMENT Under general anaesthesia the upper punctum was cannulated as above and the bleb of conjunctiva snipped off as shown in Figure 17.3. Saline then flowed from the newly created punctum when the upper one was flushed. Postoperatively the dog was discharged with neomycin, polymyxin B and dexamethasone ointment (Maxitrol, Alcon) three times daily for 5 days then twice daily for another 10 days, with instructions to gently massage the medial canthus for 5 minutes after the application of ointment. 239 OUTCOME The dog did very well. The epiphora gradually reduced over the following 3 weeks and the unpleasant smell disappeared completely. The ventral punctae were easily visible on ophthalmic examination. Mild tear overflow did continue but this was not excessive and the owner was happy to accept that it was purely cosmetic. This case illustrates that some cases of epiphora can be easily resolved with simple surgery. The unrelated multifocal retinal dysplasia is inherited and unfortunately neither the sire or dam nor the litter had been tested for this. Thankfully, the dog was mildly affected and was not intended for breeding, but it does show that owners should enquire about eye tests before purchasing puppies! CASE EXAMPLE 17.2 Patient details: Miniature poodle, 8 months old, female PRESENTATION AND HISTORY The dog was presented with persistently wet eyes. The facial skin was slightly inflamed and the dog rubbed its face along the carpet and the settee several times daily. The eyes themselves did not appear uncomfortable. The dog had been treated with topical antibiotic/steroid drops with no improvement. CLINICAL SIGNS On ophthalmic examination severe epiphora was present bilaterally. The medial skin was wet and inflamed. The lid margins were tightly opposed to the cornea and lower lid medial entropion was present. Schirmer tear test readings were 25 mm/min bilaterally – at the upper end of normal. No corneal ulceration was present but fluorescein flowed straight over the face (Figure 17.8) and did not appear at the nostrils. The nasolacrimal punctae were visible but the 240 lower ones were smaller than the upper ones. Some fine facial hairs were touching the corneal surface and a few fine hairs were also present on the caruncles in both eyes. Intraocular examination was normal. Figure 17.8 Severe epiphora in an 8-month-old miniature poodle showing fluorescein dye flowing over the face. The eyelid margins are tightly opposed to the cornea with some medial lower lid entropion. WORK-UP The dog was sedated and nasolacrimal flushing was performed. This was possible from upper to lower punctae and down the nose bilaterally, showing that anatomically the drainage system was in place, although clearly it was not functioning normally. Surgery was advised to improve tear dynamics. TREATMENT Under general anaesthesia the lower nasolacrimal punctae were enlarged, the medial caruncles were excised and lower lid entropion surgery was performed as shown in Figure 17.4. Postoperatively topical neomycin, polymyxin B and dexamethasone ointment (Maxitrol, Alcon) was dispensed twice daily for 2 weeks and 5 days 241 of carprofen 4 mg/kg/day were also supplied. OUTCOME The epiphora improved but did not fully resolve. The eyelid surgery healed well and the nasolacrimal punctae remained open. However, on blinking, some tears still drained over the face and not down the nasolacrimal ducts. It was realized that as the facial fur grew longer the tear overflow got worse, and so the owners kept the fur very short around her eyes, and used soft white paraffin ointment to protect the corneas if they saw any curly hairs touching the cornea. Although the face was still slightly wet the skin inflammation subsided. The dog did improve further as she reached maturity but the eyes were never perfect! This case shows how in some patients surgery can improve the situation but not completely cure the tear overflow. However, the owners understood the situation from the beginning and were happy that the skin was no longer inflamed and the dog had stopped rubbing her face. They had had poodles previously and thought that it was ‘normal’ for them to have some epiphora. 242  18 Dacryocystitis – chronic purulent conjunctivitis INITIAL PRESENTATION Discharge PRESENTING SIGNS Dacryocystitis is inflammation within the lacrimal sac and nasolacrimal duct. Affected animals are presented with ocular discharge – usually this is mucopurulent in nature. Alternatively, a unilateral red eye due to conjunctivitis with conjunctival hyperaemia and a variable discharge can be the initial presenting sign. It is quite common for the patient not to be brought to the surgery when the signs first develop, but only when they change and become persistent with a chronic mucopurulent discharge. The discharge is most copious at the medial canthus and reforms frequently following cleansing and removal by the owner. Sometimes the medial canthal skin is erythematous or swollen and the patient is uncomfortable. The condition is rarely encountered in cats but occurs occasionally in dogs and quite frequently in rabbits. The latter are discussed separately in Chapter 19. CASE HISTORY The patient may have history of a wet eye 1–3 weeks prior to the development of the chronic discharge and the discharge itself could have changed from serous to purulent in nature. A previous conjunctivitis or even removal of a conjunctival foreign body might have occurred. The patient can be any age or breed. Although normally unilateral in dogs, the condition can be bilateral on 243 occasion (this is more common in rabbits, as discussed in Chapter 19). CLINICAL EXAMINATION General clinical examination is usually normal in dogs. Ophthalmic examination reveals a unilateral ocular discharge centred around the medial canthus (Figure 18.1). Evidence of pain with blepharospasm or self-trauma though rubbing is variable. Conjunctival hyperaemia is normally present in the nictitans conjunctiva but can be widespread. Schirmer tear test readings are normal. No corneal disease is usually present and the rest of the ocular examination is unremarkable. On cleaning the discharge (after taking a swab for culture and sensitivity testing and cytology for Gram stain) gentle pressure at the medial canthus will often result in the appearance of further purulent material at the nasolacrimal punctae (often just the lower one but sometimes the upper as well). Fluorescein passage to the nostril is absent on the affected side (Figure 18.2); remember to compare both sides, and also that false negatives are common. Figure 18.1 Right eye of a 5-year-old golden retriever with mucopurulent discharge at medial canthus plus elevation and hyperaemia of nictitans membrane. 244 Figure 18.2 Another golden retriever with a blocked left nasolacrimal duct – notice the fluorescein at the right nostril but not the left, while it pools below the left eye. DIFFERENTIAL DIAGNOSES Chronic bacterial conjunctivitis Entropion Distichiasis Foreign body in conjunctival sac Micropunctum/imperforate punctum Keratoconjunctivitis sicca Medial canthal pocket syndrome (compare Figure 18.1 with Figure 12.1) CASE WORK-UP Nasolacrimal duct flushing is necessary to reach a definitive diagnosis and to assist with establishing the underlying aetiology, if possible. Often this can be done conscious but sedation or general anaesthesia will be required if the condition is painful or if further diagnostic tests are to be undertaken. Some purulent material can be 245 flushed between upper and lower punctae (depending which one is cannulated). Initially there is likely to be resistance to the passage of saline down the nasolacrimal duct to the nose; however, with persistence, and using steadily increasing pressure, it might be possible to establish drainage. Purulent material should be collected from the nasal ostium for bacterial culture and sensitivity testing. If the nasolacrimal flush is not successful under topical anaesthesia or sedation, then the patient should undergo general anaesthesia. Sometimes flushing from one punctum to the other in dogs will lead to the expulsion of fragments of foreign material (most commonly pieces of grass awn) which will suggest similar material down the nasolacrimal duct itself. Care should be exercised to prevent damage to the duct by overzealous flushing. If sharp pieces of foreign material are present, then exerting excessive pressure could result in rupture of the duct. If any bloodstained material is encountered, then further attempts at flushing should be discontinued. If it is not possible to establish drainage, then there are several options available. The first is to attempt retrograde flushing. This is really only feasible in medium and large sized dogs. The nasal ostium of the duct is located on the ventrolateral nasal meatus approximately 1 cm inside the external meatus. An otoscope or small vaginal speculum is useful to provide magnification and illumination when trying to locate the opening. Initial cannulation with monofilament nylon (e.g. 2/0) is achieved and this is passed up the duct as far as possible – occasionally it is stiff enough to dislodge any inspissated material as the duct widens as it approaches the lacrimal sac. A narrow gauge catheter can be introduced over the nylon thread into the nasal ostium such that retrograde flushing can be attempted. If retrograde cannulation or flushing is not feasible, then further case work-up will involve radiography – both plain and contrast studies (dacryocystorhinography). Plain radiographs might reveal 246 bony fractures or neoplastic processes which were not clinically noted. Periodontal disease involving the upper premolars or canine teeth might be present, leading to a localized inflammation in the nasolacrimal duct and subsequent obstruction. Contrast studies, using water-soluble contrast agents, can locate the exact blockage and help identify whether surgical intervention is feasible. In dogs, small amounts (1–2 ml) of contrast are injected into the upper punctum while holding the lower one closed, such that the contrast material is forced down the duct. Care should be taken to ensure that no excess contrast material is spilled as this could easily confuse interpretation of the radiographs. It is sensible to take a lateral radiograph after injecting the affected side, followed by dorsoventral or intraoral views after injecting both sides for comparison. Cystic dilations can be delineated by this method, as well as locating radiolucent foreign material. If the blockage is anterior – within the lacrimal bone for example – then referral for surgical removal can be considered. NURSING ASPECTS Frequent gentle bathing is required and owners should be shown how to do this effectively. Sterile saline on cotton wool pads or soft gauze swabs is advised. A combination of topical and systemic medication is normally necessary and again the nurse should ensure that the owner is able to medicate effectively. EPIDEMIOLOGY Dacryocystitis is usually an isolated unilateral finding in dogs and is not contagious. It is most commonly associated with infection following a conjunctival foreign body or extension of dental disease. Secondary bacterial infections are often due to mixed populations of bacteria, and culture and sensitivity testing is recommended. The lacrimal sac and nasolacrimal duct are small conduits which easily 247 become blocked. Neoplasia spreading from adjacent structures can occasionally result in dacryocystitis and traumatic fractures in the area can also lead to problems, although other clinical signs would normally assist the diagnosis in this instance. CLINICAL TIPS Temporary obstructions are easier to treat and as such early nasolacrimal duct flushing is advised Consider flushing the nasolacrimal duct immediately should a conjunctival foreign body be identified, or if the owner reports removing such an object prior to presentation with the ocular discharge Take swabs for culture and sensitivity testing from the discharge and subsequent flushings – the latter are likely to be more representative Repeat flushing every few days during treatment, especially if initial flushing is not successful TREATMENT OPTIONS – MEDICAL Initial medical treatment should involve both topical and systemic antibiotics. Broad spectrum agents are chosen such as topical chloramphenicol and systemic cefalexin until culture and sensitivity results are obtained. Repeated attempts at nasolacrimal flushing are advised every few days. If flushing is successful, then both topical and systemic treatment should be continued for 3–4 weeks – even if the clinical signs appear fully resolved before then. Failure to treat systemically, and to use too short a course of medication, are both common reasons for animals to have recurring problems. Some dogs need 6 weeks of oral antibiotics and owners should be advised that the full course of treatment should be completed to avoid relapses. If there is marked conjunctival inflammation at the medial canthus, then a short course of topical corticosteroid drops can be used alongside the antibiotics. Systemic anti-inflammatory agents such as carprofen or meloxicam can also be beneficial. 248 TREATMENT OPTIONS – SURGICAL If medical management is not successful, then surgical intervention can be considered. Referral to a suitably qualified veterinary ophthalmologist is recommended. If the nasolacrimal duct is patent then a catheter can be sutured in place for 3–4 weeks while continuing with the medical treatment outlined above. However, if a permanent blockage is present, attempts at removing this can be considered. It should be ascertained that the blockage is due to foreign material or a cystic lesion for example, rather than a neoplastic process, before surgery is undertaken. Magnetic resonance imaging might even be necessary. Surgical approaches include via the nasal chambers or from the lacrimal bone with gentle curettage of the bone over the duct. Clearly these are difficult approaches. If the duct is totally blocked, but no foreign matter is present and any infection has been fully resolved, the patient will be left with chronic epiphora. This can occur following inflammation of the duct, such that the swelling incurred at the time sticks the duct together (like a straw collapsing on itself and remaining so). Although the permanent epiphora can be worrying for the owner, it rarely is so for the patient. In many cases it can be managed with regular wiping of the serous discharge and general hygiene. However, on occasions, the patient can suffer from serious epiphora such that the skin along the face becomes inflamed and infected with a type of moist dermatitis. In these rare cases it might be necessary to recreate an alternate pathway for tear drainage. Procedures such as a conjunctivorhinostomy or conjunctivobuccostomy, where alternate routes for tear drainage are established to the nasal chambers or mouth respectively, can be undertaken as specialist procedures. 249 Figure 18.3 Decision-making tree – dacryocystitis. STT – Shirmer tear test. PROGNOSIS The prognosis for cases of dacryocystitis will depend upon the inciting cause and the duration of symptoms. Thus a relatively acute inflammation, where the duct is still patent and repeated flushing is possible, carries a good prognosis, providing treatment is continued for long enough. Stopping oral antibiotics too soon can result in recurrence. Clearly if a neoplastic process involving the nasal 250 chambers is present, the prognosis is guarded. As with so many ophthalmic complaints, early diagnosis and appropriate treatment does offer the best outcome. Thus the dog with the purulent discharge which is sent away with inappropriate topical medication could re-present 2 weeks later with a permanently blocked duct, chronic infection and persistent epiphora, while simply flushing the nasolacrimal duct at the initial consultation could have resulted in a complete cure. CASE EXAMPLE 18.1 Patient details: Golden retriever, 5 years old, male PRESENTATION AND HISTORY The dog presented with a purulent right ocular discharge which had been present for 2 months. The owner was unclear regarding its initial appearance but thought that the eye had been a bit red and weepy for a few days before she took the dog to the veterinary surgeon for an unrelated problem (grass seed in his left ear). The eye then became sticky and the owner mentioned this at the recheck for the ear. Treatment for the presumed conjunctivitis had included two different antibiotic drops and an antibiotic/steroid ointment. Although the eye improved slightly on all of these, within days of stopping the discharge returned as before. The other eye was fine and the dog was very well in himself. CLINICAL SIGNS General clinical examination was unremarkable. On ophthalmic examination the right eye had a mucopurulent ocular discharge at the medial canthus and the nictitans membrane was prolapsed and inflamed (see Figure 18.1). No corneal ulceration was noted and the bulbar surface of the third eyelid looked normal. No conjunctival foreign body was noted. Intraocular contents were normal. Fluorescein failed to flow to the nostril on the affected side, but did 251 so rapidly on the normal side. WORK-UP A swab was taken for culture and sensitivity testing prior to the instillation of fluorescein dye. After cleaning the discharge away the medial canthus was palpated. The dog showed signs of discomfort when this was done, and more purulent material exited from the lower punctum. General anaesthesia for nasolacrimal flushing was advised – the dog would not tolerate this fully conscious and since the area was painful it was thought that sedation might not be sufficient. TREATMENT Under general anaesthesia the lower punctum was cannulated but no drainage could be established. The upper punctum was cannulated and copious amounts of purulent material were flushed out from the lower punctum. A swab was taken from this material and this was sent for bacterial culture while the previous swab from the conjunctival discharge was discarded. Small fragments of grass awn were present within the purulent material (Figure 18.4). It was not possible to flush to the nose initially. A piece of monofilament nylon was used as a gentle probe down the ventral nasolacrimal punctum, but this could only be extended 1.5 cm down the duct before stopping. Some bloodstained discharge was produced. The probe was removed and the upper punctum flushed again until only clear fluid drained from the lower punctum. 252 Figure 18.4 Several pieces of grass awn flushed from the lower punctum of Figure 18.1. The patient was recovered from anaesthesia and discharged with oral cefalexin and carprofen, along with topical neomycin, polymyxin B and dexamethasone drops. Five days later the dog was anaesthetized again and repeated flushing was performed. By this stage the discharge had reduced significantly and it was possible to flush down to the nose although with moderate resistance. No further fragments of plant matter were identified. A moderate grown of mixed bacteria was isolated which were sensitive to the antibiotics prescribed. These were continued for a further 3 weeks (both topically and systemically), together with the carprofen. OUTCOME The dog continued to improve. Two weeks later it was possible to flush the nasolacrimal duct under sedation and minimal resistance to this was encountered, with saline appearing at the nostril, but no mucopurulent material. Four weeks after initial presentation 253 treatment was stopped and the dog remained clinically normal. This case illustrates how grass seeds can become lodged in the nasolacrimal canaliculus and initiate a dacryocystitis. The fact that the dog had a grass seed in the opposite ear at the same time as the eye started to show symptoms should have alerted the veterinary surgeon in attendance that a foreign body could have been present in the eye. This was not looked for (it might have been in the ventral fornix at that stage and only tracked down the duct later, or might have been visible in the punctum). Identification and removal in the first place would have avoided the chronic problem and repeated anaesthesia. Thankfully the grass awn had started to break up and did not proceed down the bony part of the nasolacrimal duct where permanent obstruction is more likely to develop. 254  19 Rabbit dacryocystitis INITIAL PRESENTATION Discharge PRESENTING SIGNS Dacryocystitis, inflammation of the nasolacrimal system, is frequently encountered in rabbits and can be a frustrating condition to manage. Since the aetiology and prognosis are different from dogs (and cats) the condition is being discussed separately. Most rabbits present with unilateral disease but on occasion it can be bilateral. The owners bring the rabbit along because the eye has a nasty discharge. This is usually a thick, whitish, sticky material and can be copious. The medial canthal fur is typically wet and matted and sometimes the rabbit is unable to open the eye as the discharge sticks the lids closed. Sometimes the animal will also show evidence of dental disease, with excessive drooling, anorexia with weight loss and grooming problems (leading to caking of the faeces and so on). CASE HISTORY The condition is normally quite gradual in onset – the owners might have been aware that the eye was a bit wet or mucky for several days, or that the rabbit had been off its food for example. There is not normally any specific history suggesting a primary infectious agent (such as the introduction of a new rabbit to the environment). The condition may have occurred previously and if this is the case the owner is more likely to present the rabbit earlier in the course of the disease. 255 CLINICAL EXAMINATION Ophthalmic examination will confirm the presence of a copious mucopurulent discharge centred around the medial canthus (Figure 19.1). Samples should be taken for bacterial culture and sensitivity (although samples from nasolacrimal flushings will be more representative – see below). The discharge can then be gently removed, including from the ventral fornix, with damp gauze swabs to facilitate examination. Conjunctival hyperaemia is normally present, often more severe at the medial canthus. Gently pressing the area will result in pus appearing from the single ventral nasolacrimal punctum. The cornea should be evaluated and fluorescein dye used – some patients will have ventromedial corneal ulceration present (presumably related to excoriation by the discharge). Intraocular contents are normally unremarkable although a mild reflex uveitis can be present. Figure 19.1 Rabbit with copious white purulent discharge and fur matting around the medial canthus. General clinical examination should pay particular attention to the teeth. Overgrowth of both incisor and molar teeth can be the primary problem, as can generalized hyperparathyroidism due to 256 imbalance in the calcium metabolism – often diet related and resulting in poor skull calcification. The rabbit’s bodily condition should also be assessed. DIFFERENTIAL DIAGNOSES Dacryocystitis can normally be readily diagnosed from the clinical examination. However, other conditions which could appear similar include: bacterial conjunctivitis conjunctival foreign body with secondary infection allergic conjunctivitis primary dental disease with secondary ocular involvement. CASE WORK-UP The most important diagnostic test, which is also an important part of treatment, is to perform a nasolacrimal flush in exactly the same way as in dogs. Most rabbits tolerate this conscious (Figure 19.2). This will differentiate dacryocystitis from a solely conjunctival disease and samples can be obtained for bacterial culture and sensitivity. Once the discharge has been bathed away, including pressing at the medial canthus a couple of times and removing the extra discharge thus produced, topical anaesthetic is instilled into the conjunctival sac. The ventral punctum is cannulated (rabbits do not have an upper punctum) and sterile saline is gently injected. It is likely that initially there will be marked resistance and backflow of purulent discharge around the cannula. However, with repeated gentle attempts hopefully the discharge will be loosened and milky fluid will drip from the ipsilateral nasal punctum. Further flushing and treatment is described below. 257 Figure 19.2 Nasolacrimal cannula in place in the sole ventral punctum prior to flushing (the discharge has been bathed away to facilitate localization of the punctum). In addition to flushing the nasolacrimal duct, careful dental examination is required, with skull radiography if indicated. The prognosis will vary depending on whether dental disease is also present and hence the importance of a complete oral examination. NURSING ASPECTS Frequent bathing of the accumulated discharge will be required and it is important to prevent matting of fur around the medial canthus. Thus clipping the fur in the area and the application of a protectant ointment such as soft petroleum jelly (Vaseline) can be useful – but it is important to ensure that this does not get in the eye. An ophthalmic formulation of soft white paraffin would be more suitable if this is a concern. General husbandry should be checked – for example, sawdust would not make suitable bedding as it could stick to the discharge and the eye, exacerbating the condition. Shredded paper might be more appropriate until the rabbit has recovered. Topical and sometimes systemic medication will be prescribed. Drop formulations are normally preferred since they will not allow further clogging in the area and will enter the nasolacrimal duct more readily. 258  Some owners find drops more difficult to apply in rabbits due to the lateral placement of their eyes and nurses should show owners the easiest way to medicate their pet. EPIDEMIOLOGY The development of dacryocystitis is multifactorial. The pathogens involved are typically opportunists – Escherichia coli, Neisseria and Streptococcus spp. and Pasteurella multocida. The last is frequently cited, and can be a primary pathogen in the rabbit, but in clinical practice is not the most frequent isolate as is often quoted. Mixed infections are common. Normally individual rabbits are affected – it is not usually a contagious disease. Any age and breed can be affected, although it is uncommon in very young animals. Dwarf breeds seem to be particularly susceptible – probably due to their brachycephalic conformation. Reduced tear drainage is necessary to allow a build-up of stagnant tears within the duct, which then becomes infected. Extension from a bacterial conjunctivitis is also possible, but less likely, and foreign bodies such as seeds and grass awns can also trigger dacryocystitis. The long, twisted nature of the nasolacrimal duct and its changes in diameter (see below) contribute to the frequency of infections. Additionally, the close association with the teeth roots (molar and incisor) and the presence of open tooth roots in rabbits are predisposing factors. CLINICAL TIPS Rabbits only have one ventral nasolacrimal punctum Pressing on the medial canthus will produce pus from the punctum Consider dental examination and radiography ANATOMY AND PHYSIOLOGY REFRESHER 259 An understanding of the anatomy of the nasolacrimal duct and its close relationship with the orbit and tooth roots (molar and incisors) is important in relation to oculodental disease. The rabbit has just one nasolacrimal punctum, situated ventromedially, and the nasolacrimal duct has a convoluted path through the lacrimal and maxillary bones. In addition to the tortuous route, the duct suddenly changes diameter several times and can easily become obstructed in its narrow sections. The duct passes close to the tooth roots of both molars and incisors and subsequently becomes involved with disease processes in the tooth roots (Figure 19.3). Figure 19.3 The anatomy of the nasolacrimal duct in rabbits: (a) lateral view and enlarged inset 260  (b) dorsoventral view showing route of duct (c) the nasal meatus opening of the duct (arrow). TREATMENT OPTIONS – MEDICAL Repeated nasolacrimal flushing and appropriate antibacterial medication is the mainstay for the treatment of dacryocystitis in rabbits. How to perform the nasolacrimal flush is described above in the section on case work-up. Normally this can be done in the conscious rabbit with the use of topical anaesthesia; however, if particularly painful, then sedation should be used. Sometimes it is not possible to flush initially. Several gentle attempts are made and if these do not result in any discharge appearing from the ipsilateral nostril, it is best to abandon attempts and treat symptomatically for 48 hours before trying again. A broad spectrum systemic antibiotic such as enrofloxacin and topical gentamicin or ofloxacin is advised. All being well, a second attempt at flushing will be more rewarding. Sterile saline should be used to flush initially and once patency has been established some authors advise a final flush with an antibiotic such as enrofloxacin. However, the pH of injectable forms can be inappropriate, causing stinging, and a 2% (1 : 50 dilution) solution of povidone–iodine might be more suitable. Always ensure that it is the solution and not the detergent formulation that is used. Catheterization of the duct, using fine nylon suture material, is very difficult due to the complicated anatomy and the risk of iatrogenic damage is high. As such it is not recommended. After successful flushing, the patient is treated with topical and systemic medication for 1–2 weeks and the nasolacrimal duct should be flushed again every few days. Once there is no further discharge it is sensible to repeat a final flush 2–3 weeks later. In some cases it is not possible to establish drainage at all. This is due to either inspissated pus completely blocking the duct or stenosis at one of the narrow or twisted regions. Dacryocystorhinography 261 can be performed to locate the area of the blockage which might correspond to tooth root problems. Addressing the dental disease, and the rabbit’s diet, might prove beneficial in such cases. TREATMENT OPTIONS – SURGICAL Surgery is rarely performed for cases of dacryocystitis. Dental extractions might occasionally be required. If permanently blocked, it is theoretically possible to create another drainage route into the nasal chambers (dacryocystorhinotomy) or mouth (dacryocystobuccostomy) but these procedures are rarely performed in dogs and cats let alone rabbits. PROGNOSIS The prognosis for cases of dacryocystitis in rabbits is poor, even if there is no underlying dental disease, but guarded if the latter is present. For simple cases, repeated flushing with antibiotic cover can be curative. However, many cases can be recurrent and pose a frustrating challenge to manage successfully. Some rabbits require life-long flushing on a monthly basis to keep the condition at bay, but an outright cure is not possible. Long-term antibiosis can also be considered. Realizing that this is an oculodental disease, and addressing feeding and other general management issues, can be beneficial. 262  4 CORNEA 263  20 Cornea – introduction Diseases of the cornea are frequently encountered in general practice and affect both dogs and cats (as well as rabbits). They can be broadly divided into those involving corneal ulceration and those which are non-ulcerative, with various subdivisions depending on cause, age at onset, appearance and so on (Table 20.1). Specific details of each disease and its management are discussed in the following sections – in this introductory part we will consider various anatomical and physio-logical factors which are applicable to most corneal disease. Table 20.1 Classification of corneal disease* Ulcerative Non-ulcerative Superficial corneal ulcer Chronic superficial keratitis (pannus) Recurrent epithelial erosion Interstitial keratitis Mid-stromal ulcer Pigmentary keratitis Deep corneal ulcer Proliferative (eosinophilic) keratoconjunctivitis Descemetocoele Keratoconjunctivitis sicca Melting corneal ulcer Corneal endothelial dystrophy/degeneration Ruptured corneal ulcer Dermoid Corneal foreign body Corneal lipidosis Corneal sequestrum Lipid keratopathy Corneal neoplasia * Bold type indicates cases discussed. ANATOMY/PHYSIOLOGY REFRESHER The cornea is the transparent anterior portion of the fibrous outer layer of the globe. It is made up of several layers – the outer 264 epithelium, the middle stroma and the inner endothelium. The acellular layer of Descemet’s membrane lies between the stroma and endothelium (Figure 20.1). In dogs and cats the corneal thickness is approximately 0.45–0.55 mm. The epithelium itself is multi-layered and non-keratinized and produces its basement membrane. Cells are attached to each other and to the basement membrane via interdigitations of the cell membranes and hemidesmosomes. The stroma is the thickest layer of the cornea, made up of multiple layers of fine collagen-containing cells. Descemet’s membrane is an elastic, acellular layer between the stroma and endothelium. The endothelium itself consists of just one layer of cells and therefore is the thinnest cellular layer. Despite its small size, the endothelium is critical for normal corneal functioning as will be seen later on. The corneal surface is bathed by the pre-ocular tear film. Further details of this can be found in the section on the nasolacrimal system (Chapter 15 and cases in Chapters 16 and 17). Figure 20.1 Cross-section of the normal cornea. Sensory innervation to the cornea is provided by the long ciliary nerves which derive from the ophthalmic branch of the trigeminal nerve (cranial nerve V). The nerves branch superficially – this means that more pain-sensitive nerve endings are present in the epithelium and anterior stroma compared to the deeper stroma and 265 is particularly relevant when considering corneal ulcers: shallow ulcers are often more painful than deeper ones, and as such one must be slightly wary when owners return for a follow-up consultation and report that their pet is much more comfortable with its eye. Hopefully this means the ulcer has healed, but it could be a worrying sign that the ulcer has actually got much deeper! The cornea has several functions. Along with the sclera, the posterior continuation of the outer fibrous coat of the globe, it provides structural support while protecting the intraocular contents. It also has a major role in both the refraction and transmission of light. It actually has more refractive power than the lens since the light rays pass from air to fluid (aqueous) as they traverse the cornea – crossing from aqueous through the lens has less refractive power. Corneal transparency is vital for normal functioning. This is maintained by the absence of blood vessels and pigment, the lattice organi-zation of the cellular structures and the small size of the collagen fibrils. The endothelium has pumps to remove extra fluid from the cornea which renders it in a relatively dehydrated state and this also assists in maintaining transparency. If this pump fails, then dense corneal oedema can result, giving a blue–grey colouration to the cornea and increased thickness. CORNEAL ULCERATION There are many potential causes for corneal ulceration; the more common ones are listed in Table 20.2. Table 20.2 Causes of corneal ulceration Underlying aetiology Examples Eyelid abnormalities Eyelid agenesis (coloboma) Entropion Blepharitis Eyelid neoplasia 266  Lagophthalmos Eyelash or hair abnormalities Ectopic cilia Distichiasis Trichiasis Nasal fold trichiasis Irritants Shampoo Smoke Acids or alkalis UV light Tear film abnormalities Keratoconjunctivitis sicca Qualitative tear film abnormalities Trauma Cat scratch Road traffic accident Blunt trauma (blow to face) Foreign body Infection Primary bacterial Primary viral Fungal (rare) Dystrophy/degeneration Corneal endothelial dystrophy Corneal oedema with glaucoma CORNEAL HEALING If the corneal surface is damaged, the method of healing depends on the depth of the wound. Superficial defects, i.e. those involving just the epithelium, normally heal by migration (epithelial sliding) and mitosis. Thus about an hour after the injury the epithelium at the edge of the lesion flattens and slides inwards to cover the gap. Mitosis of the epithelial cells then allows the structure to return to its normal thickness (Figure 20.2). If the whole of the epithelium is removed it takes only 48–72 hours for it to be replaced, although it remains thinner than normal for several weeks. Comparing how quickly a normal epithelium will heal with that in cases of refractory ulceration highlights the abnormalities present with the disease. 267 Figure 20.2 Steps in corneal healing: (a) simple epithelial defect heals by sliding and mitosis (b) deeper stromal involvement can heal by the above and slow stromal division (c) infection and toxins can result in complication and even rupture. If the corneal damage is deeper and also involves the stroma, the epithelium fills the defect in the same way, by sliding and dividing, 268 and this is followed by fibroblast proliferation in the stroma which slowly fills in the stromal defect and allows the then thickened epithelium to return to its normal depth. Thus when reassessing deeper corneal ulcers it is important to establish whether the epithelium has grown across the bottom of the defect and carefully flushing out any excess fluorescein will assist with this diagnostic test. Stromal injuries will result in more scarring than if the epithelium only is damaged. This is mainly due to the transformation of stromal keratocytes into fibroblasts. These interrupt the normal alignment of the fine stromal lamellae and result in permanent opacification. Blood vessels also grow into the damaged cornea from the limbus. These are a mixed blessing, since although they bring leucocytes and various growth factors to the damaged area, they can also predispose to excessive inflammation, including granulation tissue formation, and further scarring can ensue. Obviously vascularization can also be a factor in non-ulcerative corneal disease and the specific pathology of this will be mentioned if relevant for the cases discussed later. Deep injuries, or ulcers which are progressing (perhaps due to infection), can result in rupture of Descemet’s membrane. This elastic, non-cellular layer is normally under some tension, and if ruptured will coil back on itself and rarely re-forms a complete layer afterwards. Healing of the endothelium is limited since these cells have minimal regenerative capabilities in dogs and cats. As such, they heal by hypertrophy and sliding, rather than by mitosis, and this ability is limited. Corneal oedema is common if the endothelium is damaged, and can be permanent. 269 Figure 20.3 Decision-making tree – corneal ulcer. GK – grid keratotomy. CORNEAL COLOUR CHANGES As with most ocular pathology, there is only a limited number of ways the cornea can react to insults. Since the cornea is usually transparent, the colour change which occurs following disease is the most striking alteration and can be divided into white, red, blue– grey or pigmented lesions, as listed in Table 20.3. We will encounter these as we discuss the different corneal conditions in the following sections. Table 20.3 Common causes of corneal colour change Colour Cause Red Neovascularization Stromal haemorrhage Symblepharon Neoplasia (rare) White Dense oedema Lipid Calcium deposits 270  Leucocytes Stromal scarring Keratic precipitates Blue–grey Mild corneal oedema Keratomalacia with infectious agents Pigmented Superficial melanin deposition Corneal sequestrum Corneal endothelial pigment (from uveal cysts) 271  21 Recurrent epithelial erosion INITIAL PRESENTATION Discharge, abnormal appearance – red PRESENTING SIGNS Dogs and cats with recurrent epithelial erosions typically present with mild conjunctival hyperaemia, increased lacrimation and slight blepharospasm in the affected eye. Breeds typically presented include boxers and corgis although any middle-aged dog can be affected, including crossbreeds. Burmese and Persian cats tend to be over-represented compared to the general feline population. Commonly only one eye is affected but occasionally both eyes are involved at the same time. The degree of discomfort is variable – some patients do not seem sore, while others try to rub the affected eye from time to time. A few patients are particularly uncomfortable although this is quite uncommon. There may be a change in appearance of the eye – the cornea is sometimes slightly oedematous, giving a grey–blue cloudiness to the ulcerated area while some conjunctival hyperaemia is inevitable. Sometimes a secondary bacterial infection can develop and in these cases the ocular discharge will change from serous to mucopurulent in nature and the owner might present the patient because of the discharge