Clinical Examination in Ophthalmology PDF

 CLINICAL EXAMINATION IN OPHTHALMOLOGY “This page intentionally left blank"  CLINICAL EXAMINATION IN OPHTHALMOLOGY P.K. Mukherjee, MS Former Dean, Professor and Head...

 CLINICAL EXAMINATION IN OPHTHALMOLOGY “This page intentionally left blank"  CLINICAL EXAMINATION IN OPHTHALMOLOGY P.K. Mukherjee, MS Former Dean, Professor and Head Department of Ophthalmology Pt. J.N.M. Medical College Raipur, India ELSEVIER A division of Reed Elsevier India Private Limited Clinical Examination in Ophthalmology, 2/e Mukherjee ELSEVIER A division of Reed Elsevier India Private Limited Mosby, Saunders, Churchill Livingstone, Butterworth Heinemann and Hanley & Belfus are the Health Science imprints of Elsevier. © 2006 Elsevier All rights are reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the publisher. ISBN-13: 978-81-312-0335-4 ISBN-10: 81-312-0335-2 Medical knowledge is constantly changing. As new information becomes available, changes in treatment, procedures equipment and the use of drugs become necessary. The authors, editors, contributors and the publishers have, as far as it is possible, taken care to ensure that the information given in this text is accurate and up-to-date. However, readers are strongly advised to confirm that the information, especially with regard to drug dose/usage, complies with current legislation and standards of practice. Published by Elsevier, a division of Reed Elsevier India Private Limited, Sri Pratap Udyog, 274, Captain Gaur Marg, Sriniwaspuri, New Delhi – 110065, India. Printed and bound in India at  To my teachers who ignored my ignorance and To my students who were ignorant of my ignorance “This page intentionally left blank"  P REFACE Whenever a new book is published, the most often asked question is, “Yet another book, but why?” Robert Hutchison the author of Hutchison’s Clinical Methods in 1897 answered it very well, “It is not intended as a treatise upon clinical diagnosis. On that subject there are already suffi- ciency of good works in existence.” The present author also subscribes to this statement more than a century after Hutchison. In fact there is no shortage of textbooks in ophthalmology, many of which are written in a superb fashion. Most of these books, generally concise, contain a chapter on examination of the eye, which is not sufficient for an undergraduate student. Hence this book. However, the author does not claim to have produced a book that answers all questions which come to the minds of the students nor is this book the last word in examination of the eyes. Having been a teacher and an examiner for many years, the author has realized that both undergraduates and postgraduates may be able to form a diagnosis but fumble miserably when asked, how? or why? A resident is known to order a battery of costly investigations to prove his theoretical knowledge without bothering to do simple outdoor procedures like recording of vision, use of pin-hole, cover test or listen carefully to the complaints of the person, which may in fact lead to diagnosis and provide a clue to appropriate investigations. The book is addressed primarily to undergraduate students; however this book will be a good foundation for postgraduates too. The book has not been written in the Queen’s English deliberately. It has been written in English that is spoken in the third world. The book includes general information regarding signs, symptoms and terminology. Each chapter is devoted to a system of the eye. There are some repetitions in various chapters, prima- rily in order to emphasize the importance of certain key facts. For details of sophisticated and specialized investigations and their interpretations, the postgraduates are advised to consult standard references on such subjects. Management of various diseases is out of this book’s limit, hence has not been included. In spite of the author’s best efforts, it is unlikely that this book is free from inaccuracies like typographic errors, statistical ambiguities, etc. Feedback from teachers and students will be most welcome in order to remove them and improve the book. P.K. Mukherjee “This page intentionally left blank"  ACKNOWLEDGEMENT I am thankful to my students who for years have been urging me to publish my notes in a book form. It is their desire that has prompted me to put my thoughts on examination of eyes in a book form. I am thankful to Elsevier, a division of Reed Elsevier India Private Limited, for publishing the book. I am thankful to their officers especially Shri Tanveer Ahmad, Shri Rajiv Banerji, Ms. Shabina Nasim and other members of the staff for their cooperation and help in getting this book published. I profusely thank members of the upgraded Department of Ophthalmology, Pt. J.N.M. Medical College, Raipur for the help that they have rendered to me. Prof. S.L. Adile, Prof. A.K. Chandrakar, Dr. M.L. Garg, Associate Professor, Dr. Nidhi Pandey, Assistant Professor, Dr. Subhash Mishra and Dr. B.K. Das of the Mobile Unit have been generous enough to give me books and journals for reference. I thank them profusely. I am also thank- ful to Dr. Dilip Agrawal, Plastic Surgeon, Raipur, Dr. Alka Das, Ophthalmic Consultant, Raipur and Dr. Madan Kumar Deshpande, Ophthalmic Consultant, Bilaspur, for permitting me to use the photograph of their patients from their collection. I am thankful to Dr. K. Appa Rao, Dr. Sunil Gupta, Dr. Santhosh Patel. I am thankful to Dr. Manik Chatterjee, Assistant Anatomy, Dr. Preeti Gupta, Consultant Ophthalmologist and Dr. B.P. Sharma, Consultant Ophthalmologist, Bhilai, for having provided me with their personal books. I am thankful to Padmashree Dr. A.T. Dabke for helping me in collecting the photographs of my patient over the years. The real inspiration behind this book remains my wife, Protima. My daughters, Protibha and Preeti kept on pestering me to keep to the time schedule and even permitted their respective spouses Satyadeep and Abir to spend their holidays in typing the manuscript and rearranging them many a time. They also laboured very hard in drawing and re-drawing the figures. They all deserve thanks. I am thankful to Shri Maneesh Dandekar of HyperSoft Computers, Raipur for typing of the book. P.K. Mukherjee “This page intentionally left blank"  C ONTENTS Preface vii Acknowledgement ix Chapter 1 Symptomatology and History Taking 1 Chapter 2 Examination of Vision and Recording of Visual Acuity 14 Chapter 3 Examination of Eyes Under Diffuse Light 37 Chapter 4 Examination of Eyes Under Focal Illumination 42 Chapter 5 Examination of the Lid 49 Chapter 6 Evaluation of a Case of Ptosis 65 Chapter 7 Examination of the Lacrimal System 74 Chapter 8 Examination of the Conjunctiva 81 Chapter 9 Examination of the Globe, Cornea and Sclera 100 Chapter 10 Evaluation of an Eye with Disorder of Tear Film 127 Chapter 11 Examination of Anterior Chamber 134 Chapter 12 Examination of Iris, Ciliary Body and Choroid 141 Chapter 13 Examination of Lens and Evaluation of an Eye for Lens Extraction 158 Chapter 14 Measurement of Intraocular Tension 173 Chapter 15 Examination of Eyes with Abnormal Intraocular Tension 180 Chapter 16 Examination of the Eyes Requiring Optical Correction 213 Chapter 17 Examination of a Case of Squint 232 Chapter 18 Neurological Examination of the Pupil 278 Chapter 19 Examination of the Orbit and Radiology of Ophthalmic Interest 285 Chapter 20 Examination of Retina and Macula 309 Chapter 21 Examination of Vitreous 343 Chapter 22 Examination of the Optic Nerve and the Visual Pathway 349 Chapter 23 Examination of Eyes in Paediatric Age 365 Bibliography 372 Index 379 “This page intentionally left blank"  CHAPTER 1 S YMPTOMATOLOGY AND H ISTORY TAKING Symptoms comprise complaints of the person regarding the disease he or she is suffer- ing from and signs are clinical features that an examiner notices or elicits. Some of the symptoms are signs by themselves, e.g. deviation of eye in a particular direction. This is an obvious complaint of the patient but is also a sign, which requires further examination to find out if it is paralytic or non-paralytic, if it is a simple deviation or is associated with diminished vision, and if the diminished vision can be improved. Redness around the cornea is an important sign that patients first notice and report. Many times symptoms provide an important clue towards diagnosis, e.g. if a per- son of forty years complains of difficulty in reading but has no difficulty in distant vision, the obvious diagnosis is presbyopia. An adult with gradually diminishing night vision is most probably a case of retinitis pigmentosa. It is important to listen carefully to what the patient has to say in his or her own words. SYMPTOMS IN OPHTHALMIC DISORDERS Symptoms in ophthalmic disorders are as follows: A. Ocular B. Non-ocular Ocular Symptoms Ocular symptoms can be: 1. Visual 2. Non-visual 3. Mixed Visual Symptoms of Ocular Disorders Diminished distant vision Diminished near vision Diminished distant as well as near vision Diminished night vision Diminished day vision Diminished colour vision Diminished field of vision 2 CLINICAL OPHTHALMOLOGY Diminished vision in bright light Diplopia Polyopia Metamorphopsia Photopsia Chromatopsia Coloured haloes Glare Photophobia Frequent change of glasses Visual symptoms are brought about by: Errors of refraction Anomalies of accommodation Opacities in media Pathology in optic pathway, retina and choroid Disturbance of ocular motility Neurological Amblyopia Diminished distant vision Diminished distant vision is the commonest visual symp- tom for which a person seeks help. It surpasses all other symptoms. Diminished distant vision can be unilateral or bilateral. It is seldom equal in both eyes. Differences may vary from slight to severe. It could be gradual or sudden in onset. It could be associated with non-visual symptoms like pain, redness, watering or could just be gradual without any other symptoms. Again, gradual painless diminished distant vision surpasses other painful symptoms. Causes of gradual painless diminished distant vision are: (a) Errors of refraction (b) Gradually developing opacities in ocular media (c) Chronic optic neuropathy Chronic glaucomas, primary or secondary, produce diminished distant vision when they are well advanced Heredofamilial optic neuropathy Consecutive optic atrophy Secondary optic atrophy Drug-induced neuropathy (d) Chronic maculopathy Macular degenerations and dystrophies Cystoid macular oedema Diabetic maculopathy Chronic macular oedema, secondary to vascular lesion, inflammation, trauma or drug induced (e) Chronic retinopathy Diabetic retinopathy Hypertensive retinopathy Branch artery occlusion Branch vein occlusion Sub-retinal neovascularisation  SYMPTOMATOLOGY AND HISTORY TAKING 3 (f) Amblyopia Anisometropic Strabismic Ex anopsia (form vision deprivation) (a) Errors of refraction are myopia, hypermetropia and astigmatism (b) Ocular media are cornea, aqueous, lens and vitreous Most frequent gradually increasing opacity in ocular media is immature cataract, followed by opacities of cornea, which may be post-traumatic and post-infective, vascularisation of cornea, degenerations, dystrophies and deposits on the cornea Aqueous is not capable of being opaque.Vitreous opacities are common but do not produce visual loss unless they are very large or present in front of and near macula (c) Chronic optic neuropathy (d) Chronic maculopathy In amblyopia, gradual painless unilateral diminished vision may go unnoticed by the patient especially in the absence of other symptoms like squint, corneal opacity, etc. It is detected either on routine checkup or when the patient closes the seeing eye and for the first time realises diminished vision in the other eye. It is generally due to errors of refraction developing after six or seven years of age, or small angle tropias or faint cen- tral corneal opacities. These eyes are generally not capable of improvement. Sudden loss of distant vision can be painful or painless. Causes of sudden painful loss of distant vision are: 1. Trauma 2. Corneal ulcer 3. Herpes zoster ophthalmicus 4. Interstitial keratitis 5. Acute iridocyclitis 6. Acute congestive glaucoma 7. Endophthalmitis Causes of sudden painless loss of distant vision are: 1. Central artery occlusion 2. Retinal vein thrombosis 3. Vitreous haemorrhage in front of macula 4. Macular haemorrhage 5. Retinal detachment 6. Central serous retinopathy 7. Acute ischaemic optic neuropathy 8. Cortical blindness 9. Malingering All the above causes are generally unilateral. For a bilateral sudden loss of vision, the lesion is generally vascular involving both the visual pathways. Causes of bilateral sudden loss of vision are: 1. Cortical blindness 2. Hysterical patient sometimes report bilateral sudden painless loss of distant vision 3. Malingering 4 CLINICAL OPHTHALMOLOGY 4. Uraemia 5. Methyl alcohol poisoning 6. Quinine toxicity Diminished near vision It could be gradual or sudden. Generally, gradual dimin- ished near vision is bilateral and equal. It is universal after 45 years of age. If a person after age of 45 years does not develop diminished near vision then there are only two possibilities, i.e. he is myope or does not have to undertake near work at usual near distance of 30 cm. Causes of gradual diminished near vision are: 1. Presbyopia 2. Posterior capsular cataract 3. Posterior polar cataract 4. Macular degeneration 5. Bilateral large corneal opacity on the nasal side Causes of sudden diminished near vision are: 1. Instillation of cycloplegic for therapeutic or diagnostic purpose. It can be accidental or psychogenic (cycloplegia with atropine may last as long as fortnight) 2. Internal ophthalmoplegia 3. Total ophthalmoplegia 4. Spasm of accommodation 5. Iatrogenic (a) Aphakia (b) Pseudophakia (c) Over correction of myopia (d) Under correction of hypermetropia (e) Systemic parasympatholytic drug administration Diminished distant as well as near vision It is seen in uncorrected aphakia, pseudo- phakia, advanced cataract, macular degeneration, corneal degeneration and dystrophy, and uncorrected errors of refraction. Diminished night vision By far the commonest cause of diminished night vision is vitamin A deficiency followed by retinal dystrophy. It should be remembered that: ➤ If a child under five years of age presents with diminished night vision, it is most probably due to vitamin A deficiency and will improve with therapeutic dose of vitamin A ➤ An adult with night blindness is most probably suffering from retinitis pigmentosa and will not improve with administration of vitamin A Diminished colour vision This is commonly known as colour blindness. However, as there is no change in visual acuity due to the diminished colour sense, it is not appropriate to designate it as blindness. The commonest cause of this defect is genetic, seen almost exclusively in males. About 4–8% of male population have colour vision defects not amenable to treatment, and patients are generally unaware of the defect unless it is specifically tested for, or causes social embarrassment in the form of choice of dress.  SYMPTOMATOLOGY AND HISTORY TAKING 5 Other causes of diminished colour vision are acquired, e.g. immature cataract, optic neuritis and macular degeneration. Diminished field of vision (scotoma) Loss of field is called scotoma. It could be cen- tral or peripheral, unilateral or bilateral, simultaneous or one may follow the other. One eye may have more advanced scotoma than the other. A scotoma is said to be positive if the person is aware of its presence and negative when the person is not aware of it. Blind spot is a physiological negative scotoma. In the long-run positive scotomas can become negative, while the reverse is not possible. A scotoma is called relative when its density or shape changes with illumination or colour. In case of relative scotoma the patient seems to see through a haze. Patients describe scotoma in various terms. Patients may complain that they have to move their head to see an object on one side. Hemianopias are generally spoken of as diminished vision. Central field defects are also reported as diminished vision. Causes of central scotoma are: 1. Optic neuritis 2. Retrobulbar neuritis 3. Macular lesions Peripheral scotomas are produced by lesions of retina, optic nerve and optic pathway. Causes of peripheral scotoma are: 1. Advanced glaucoma, mostly primary 2. Retinal dystrophy, retinitis pigmentosa and related conditions 3. Choroidal dystrophy 4. Retinal detachment 5. Acute ischaemic optic neuropathy 6. Pituitary tumours 7. Post-papilledematous optic atrophy 8. Drug induced 9. Lesions of chiasma, optic tract and optic radiation Scotoma can be congruous or incongruous; it can be homonymous or heteronymous. Congruous field defects are those defects where the edges of the scotoma in each eye are symmetrical. Homonymous field defects are those defects that are situated on the same side of visual field, e.g. right nasal and left temporal. Heteronymous field defects are those that are situated on the same position, e.g. right temporal defect and left tempo- ral defect of right and left eye, respectively. Diminished vision in bright light (diminished day vision) Patients complain that they have good vision in the evening or at night, but in bright light their vision is greatly reduced. Common causes of diminished vision in bright light are: 1. Posterior polar cataract 2. Central nuclear cataract 3. Macular lesions 4. Central corneal opacity Diplopia (seeing double) The patient sees two images of a single object. The main image has a sharp outline. The second image is fainter, may partially overlap the first 6 CLINICAL OPHTHALMOLOGY image or may be separated by a gap. It may be displaced horizontally or vertically, may be tilted, the distance between the two images may change in different gazes and may disappear with compensatory change in head posture. Both the images may be on the same side or may cross over mid-line. If diplopia disappears by closing one of the eyes, it is known as binocular diplopia. If diplopia disappears by obstructing the affected eye, it is called uniocular diplopia. The commonest cause of binocular diplopia is paralytic squint, other causes being restrictive strabismus, dysthyroid oculopathy, blow out fracture of the orbit, post- operative entrapment of muscles in retinal surgery, myasthenia gravis, retrobulbar growth, and trauma to muscles. Uniocular diplopia is relatively rare. Causes of uniocular diplopia are: 1. Recent corneal opacity 2. High astigmatism 3. Subluxated lens 4. Iridodialysis 5. Displaced IOL 6. Retinal detachment Polyopia (seeing multiple) The patient complains of seeing multiple images of linear or crescent-shaped lights, commonly moonlight and streetlight. It is seen in incipient stages of immature cataract. Metamorphopsia (distorted vision) In metamorphopsia objects look distorted. They may look smaller—micropsia or larger—macropsia. Lines may look wavy. Metamorphopsia may be seen in retinal detachment, macular oedema, macular degen- eration, and central serous retinopathy. Photopsia (flashes of light) The patient complains of flashes of light in the periph- ery of field of vision. These are transient and recurrent, and are best appreciated in the dark. They imply retinal or cerebral irritation. They may be a warning symptom of impending retinal detachment. They are also seen in posterior vitreous detachment. Chromatopsia (coloured vision) The patient complains that light-coloured objects like whitewashed wall, white clothes, etc. seem to be tinged. If the tinge is blue, which is very common, it is called cyanopsia, if the tinge is red it is called erythropsia, and yellow is xanthopsia. Coloured haloes around lights Rainbow-like haloes are seen around artificial lights in dark surroundings. They could be unilateral or bilateral. They are caused by the splitting of white light into seven colours due to the prismatic effect of fluid in the cornea or lens. They are seen in prodromal stage of acute congestive glaucoma, corneal oedema and incipient stage of cataract. In acute mucopurulent conjunctivitis, mucus shreds on cornea may have prismatic effect and produce coloured haloes that disap- pear with the removal of mucus. Glare (discomfort of bright light) The patient does not like bright light. This is to be differentiated from photophobia.  SYMPTOMATOLOGY AND HISTORY TAKING 7 Glare is seen in: 1. Large pupil 2. Myopia 3. Use of mydriatic and cycloplegic 4. Immature cataract 5. Recent aphakia 6. Large iridectomies 7. Albinism Photophobia (intolerance to light) The patient is not able to tolerate light and may close the eye or move the head away from the source of light. This is associated with forceful closure of lids. Photophobia can be unilateral or bilateral. Photophobia is more marked in children. Causes of photophobia are: 1. Trauma to the cornea 2. Embedded foreign body in the cornea 3. Interstitial keratitis 4. Rupture in the Descemet’s membrane 5. Phlyctenular keratoconjunctivitis 6. Acute iridocyclitis 7. Chemical burn 8. Ultraviolet light exposure (welding, snow blindness) Frequent change of glasses Change of power every year or alternate year is com- mon. A myopic child requires increased power every year. A presbyope may require a change every second or third year. If a person feels uncomfortable with glasses and requires change frequently, this should receive attention. Causes of frequent change of glasses are: 1. Keratoconus 2. Central nuclear cataract 3. After cataract 4. Chronic simple glaucoma 5. Hypoglycaemia 6. Hyperglycaemia 7. Macular oedema 8. Retrobulbar growth 9. Hypotony 10. Subjective prescription of glasses in children Visual agnosia: Inability to recognise familiar object by sight, for example the patient may not be able to recognise a watch but can identify it with its sound or by touch. Visual hallucinations: They may be formed or unformed. Formed hallucinations represent objects, persons and animals that are not actually present. Unformed hallucina- tions represent vague forms, lights and colours. Dyslexia: Impaired ability to comprehend the written words (reading difficulty) in the presence of good vision and hearing, generally seen in children who may be stigmatised as dull or mentally retarded. Dyslexia in milder form may persist in adults, and go unnoticed. 8 CLINICAL OPHTHALMOLOGY Non-Visual Symptoms of Ocular Disorders Like visual symptoms, the list of non-visual symptoms is also very long, which may be associated with visual symptoms as well. They are: (a) Redness (b) Watering (c) Discharge (d) Dryness (e) Itching (f) Pain in and around the eye (g) Change in appearance of the eye (h) Growth of the eye and its adnexa (i) Change in colour of the cornea (j) Change in colour of the pupil (k) Change in colour of the lids (l) Whitening of eyebrow and lashes (m) White spot on the conjunctiva (Bitot’s spot) Redness of the eye This is a very common symptom. It can be associated with pain or may be painless. It can be unilateral or bilateral, generalised or localised. It may be associated with watering discharge, displacement of globe, diminished vision, etc. Causes of redness of the eye are: 1. Conjunctivitis—infective or allergic 2. Trauma 3. Sub-conjunctival haemorrhage 4. Keratitis 5. Iridocyclitis 6. Acute and chronic congestive glaucoma 7. Episcleritis and scleritis 8. Pterygium 9. Conjunctival growth Causes of redness of the eye with pain are: 1. Trauma 2. Acute iridocyclitis 3. Keratitis 4. Corneal ulcer 5. Herpes zoster 6. Acute congestive glaucoma 7. Episcleritis and scleritis 8. Endophthalmitis Causes of redness of the eye without pain are: 1. Simple allergic conjunctivitis 2. Spring catarrh 3. Phlycten (conjunctival) 4. Pterygium 5. Non-traumatic sub-conjunctival haemorrhage  SYMPTOMATOLOGY AND HISTORY TAKING 9 6. Angular conjunctivitis 7. Trachoma 8. Chronic dacryocystitis ➤ Unilateral redness of eye is seldom conjunctivitis ➤ Other causes of redness should be looked for ➤ Bilateral redness of eyes need not be conjunctivitis always Watering from the eye Normal eyes are always wet; however an average person is not aware of the wetness. A person becomes aware when either there is excessive pro- duction of tear or there is normal tear production with inadequate drainage. Tradi- tionally, the former is called lacrimation and latter epiphora. Recently, it has become common practice to use epiphora for both; and lacrimation is only referred to as reflex epiphora. Lacrimation is always due to irritation of the fifth nerve in the eye, adnexa or sur- rounding structure. It can also be psychological in nature. Causes of lacrimation are trauma, foreign body, allergy, infective conjunctivitis, corneal ulcer, keratitis, lagophthalmos, proptosis, entropion, trichiasis and ectropion. Causes of epiphora are coloboma of lower lid, lagophthalmos, ectropion of lower lid and puncta, obstruction of puncta and canaliculi, chronic dacryocystitis, absence of sac, and nasolacrimal duct blockage. ➤ Acute watering is generally lacrimation ➤ Prolonged watering is invariably epiphora Discharge from the eye Discharge from the eye may be from the conjunctiva, lacrimal sac or orbital sinus. Conjunctival causes of discharge can be mucopurulent conjunctivitis, or purulent due to ophthalmia neonatorum, gonococcal conjunctivitis in adults. Ropy discharge is characteristic of spring catarrh. Chronic dacryocystitis may be associated with mucopurulent or purulent discharge on pressing the sac. A discharging sinus of orbit or paranasal sinus may open in the conjunctival sac. Blood discharge is seen in cases of trauma, membranous and pseudo-membranous conjunctivitis, papilloma of the conjunctiva, haemangioma of conjunctiva, oculo- sporidiosis, blood dyscrasia and haemorrhagic conjunctivitis. Dryness of the eye (scanty tear formation) Generally the patient does not com- plain of reduced tear formation but complains about irritation, pain and redness, which are produced by scanty tears. When dryness of the eye is pointed out to the patient, then the patient may come forward with the information that even during crying, there is either very little or no water. Causes of dry eye are grouped under dry eye syndromes (see Chapter 11). Itching of the eye Itching of the eye is very common in children; it is generally bilateral and seasonal. It may also be seen in adults and may be perennial. 10 CLINICAL OPHTHALMOLOGY Causes of itching of the eye are spring catarrh, acute allergic conjunctivitis, seasonal allergic conjunctivitis, perennial allergic conjunctivitis, giant papillary conjunctivitis, systemic allergy, chronic follicular conjunctivitis, blepharitis and drug-induced aller- gic conjunctivitis. ➤ Trachoma, pterygium and phlycten do not cause itching per se Pain in and around the eye Causes of pain in the eyeball are trauma, iritis, irido- cyclitis, acute and chronic congestive glaucoma, corneal ulcer, herpes zoster, episcleri- tis, scleritis, endophthalmitis and absolute glaucoma. Causes of tenderness in the eyeball are iritis, iridocyclitis and retrobulbar neuritis. Causes of pain on movement of the eye are retrobulbar neuritis, optic neuritis and myositis. Causes of pain around the eye are stye, infected chalazion, lid abscess, acute dacry- ocystitis, dacryoadenitis, orbital cellulitis, superior orbital fissure syndrome, cavernous sinus thrombosis, lid abscess, fracture of orbit, sinusitis, herpes zoster and trigeminal neuralgia. Causes of tenderness in periocular structures are trauma, stye, infected chalazion, lid abscess, acute dacryocystitis, acute dacryoadenitis, sinusitis and fractured orbit. ➤ White eyes are generally not painful ➤ Yet all red eyes need not be painful Change in appearance of the eye Causes of change in appearance of the eye are: 1. Narrow palpebral aperture: Ptosis, pseudoptosis and soft eye 2. Wide palpebral aperture: Lagophthalmos and lid retraction 3. Proptosis and exophthalmos 4. Squint 5. Pterygium, growth of conjunctiva, corneal opacity and staphyloma 6. Loss of eyebrow: Idiopathic, senile, hypothyroidism, leprosy and burns 7. Loss of eyelashes: Idiopathic, senile, blepharitis, trachoma and burns Growth of the eye and its adnexa Intraocular growths go unnoticed until they produce other symptoms of loss of vision, pain, redness, etc. Extraocular growths are prominent. They can arise from lid, lacrimal gland, conjunctiva and orbit. They can be benign or malignant, primary or secondary. Change in colour of the cornea This may be due to corneal opacity or corneal ulcer, blood staining of cornea, blood in anterior chamber and tattooing. Change in colour of the pupil This may be due to congenital cataract, traumatic cataract, senile cataract, retinoblastoma or other diseases simulating retinoblastoma. Change in colour of the lids If the colour of lid turns white, it may be due to albinism, vitiligo, leprosy, burns, scar, sympathetic ophthalmia and Vogt Koyanagi syndrome. If the colour of lid turns dark, it may be due to birthmark, haemangioma, neuro- fibromatosis, nevus, black eye, spring catarrh or idiopathic.  SYMPTOMATOLOGY AND HISTORY TAKING 11 Whitening of eyebrows and lashes The causes are physiological, sympathetic ophthalmia, Vogt Koyanagi syndrome and albinism. Mixed Symptoms of Ocular Disorders There are many conditions where both visual and non-visual symptoms coexist. Some examples are errors of refraction and squint, squint and amblyopia, pterygium and diminished vision. There can be many such combinations. Non-Ocular Symptoms The commonest non-ocular symptom with which the patient comes to the ophthal- mologist is headache followed by vertigo. Most frequent non-ocular symptom with which a patient is referred to ophthalmic checkup is also headache. Acute headaches without ocular signs are most often not related to eye. Ocular causes of headache con- stitute a small group of causes. Some of the important ocular causes of headache are: 1. Uncorrected error of refraction: Large errors of refraction are less likely to cause headache. Myopia causes headache less frequently than hypermetropia. Astigmatism is a very common causes of ocular headache; oblique axis causes more trouble than vertical or horizontal axis. 2. Wrong glasses: Hypermetropic children may be prescribed myopic glasses Presbyopia: Uncorrected, over or under corrected 3. Accommodation and convergence disparity 4. Muscle imbalance: Both phorias and tropias can cause headache. Paralytic squint can cause headache, or headache may be due to raised intracranial tension, hypertension or diabetes. Muscle imbalance for near can especially cause headache Headache radiated to the distribution of the fifth nerve on the same side can be due to iritis, iridocyclitis, acute and chronic congestive glaucoma, absolute glaucoma, endoph- thalmitis, panophthalmitis, proptosis, Tolosa Hunt syndrome, oculomotor palsy due to posterior communicating artery aneurysm or diabetes, chronic granuloma of orbit and post-herpetic neuralgia. ➤ Posterior uveitis and retinitis do not produce headache or pain in the eye ➤ Spectacles will not relieve headache unless it is due to asthenopia ➤ Headache may be independent of error of refraction HISTORY TAKING IN OCULAR DISORDERS History of a disease is the keystone that binds subsequent diagnosis in all branches of medicine; ophthalmology is no exception. It is rewarding to take a proper history and cor- relate it with the symptoms. Some of the symptoms and their clinical presentation may directly lead to a diagnosis. For example, a school going child finds it difficult to see the letters on the blackboard in the classroom but has no difficulty in reading his books. Obviously this child is suffering from an error of refraction, most probably myopia. In contrast to this, a grandfather who has been using glasses for reading finds that, of late, 12 CLINICAL OPHTHALMOLOGY he can read his newspaper without glasses, although his distant vision has diminished considerably. This indicates that he is suffering from central nuclear sclerosis. There are numerous instances where history directly leads to diagnosis. A patient may use local jar- gon or a term that may mean different symptoms to different persons especially the cli- nician. A patient may report that he has night blindness. On questioning it is revealed that he actually finds it difficult to read at night due to dim illumination. In fact he is suf- fering from presbyopia. Pain is a very personal sensation. Threshold of pain varies among individuals; chil- dren have better tolerance for pain but are more apprehensive about the mode of treat- ment. Many adjectives are prefixed to pain, e.g. mild, severe, dull, throbbing, bursting, boring, etc. However, history alone is not always sufficient in clinical ophthalmology. It should be backed by clinical signs, symptoms, usual clinical procedures, routine investigations and special investigations. History should be elicited under following heads: 1. History of present illness 2. Past history of ocular and non-ocular diseases and treatment taken 3. Allergy and drug reaction 4. Family history 5. Occupation 6. Personal history History of Present Illness History of present illness should give information regarding the onset of disease, whether sudden or gradual, acute exacerbation on chronic disease and recurrence of a treated disease. In acute cases patient may be able to state not only the date of onset but also the hour of onset. In chronic cases the patient is not very sure of the date and time. Unilateral or bilateral: If bilateral, did the other eye get involved simultaneously or was there a gap of some days, and if the condition is equal in both eyes. Symptoms: Visual, non-visual or combination of both. Is it painful or painless. The exact location of pain or tenderness. Does it radiate? Is there an improvement with treatment? Has it remained the same? Has it worsened? Treatment: Has the patient taken any treatment, may be a home remedy, or prescribed by a general practitioner or a specialist. Details of medicine, its dose and frequency should be noted. Trauma: Trauma is one of the major causes of ocular morbidity. A child may pre- fer to hide history of trauma, while in a medico-legal or labour dispute, the patient may try to overplay the role of trauma. Past History Past History of Ocular Disease It may be related to the present disease, e.g. history of blunt injury leading to the development of cataract, hyphaema or even rupture of globe and retinal detachment. Stye, chalazion and infective conjunctivitis in childhood cannot be correlated to cataract or glaucoma in later life but a child who has been under treatment for spring  SYMPTOMATOLOGY AND HISTORY TAKING 13 catarrh by steroids may develop diminished vision due to steroid-induced cataract, glaucoma or both. A patient may have a disease in the other eye, which is not related to the present disease or a similar disease may develop in other eye later. Common examples are iridocyclitis, episcleritis, scleritis, myopic retinal detachment and age- related macular degeneration. Past history of surgery: Common instances are a patient of amblyopia who has had squint correction, a patient of retinal detachment with a history of lens removal, or someone with hypotony following glaucoma surgery. Question should be asked regarding the age at which the surgery was done? Was it followed by another opera- tion? Did the vision improve following surgery? (The patient may not be able to state the exact nature of surgery performed.) Spectacles: It should be ascertained whether the glasses are for distance, near or both; age at which the glasses were prescribed for the first time and the purpose of it. Has the power changed since then and if so how often and how much? Could the patient read the last line in the vision chart when last prescribed? Were they prescribed by a qualified optometrist, optician or ophthalmologist or by a non-qualified person? Past History of Systemic Disease (a) Infective diseases—tuberculosis, syphilis, leprosy, gonorrhoea, diptheria and meningitis (b) Metabolic disorders—diabetes and dysthyroid state (c) Autoimmune diseases—rheumatoid arthritis, Reiter’s disease and Still’s disease Allergy and Drug Reaction (a) Exogenous: Dust, fume, pollen, husk, fur, nylon, wool and food (b) Endogenous: Patient may not be able to state (c) Drug: Local instillation of antibiotics, atropine, pilocarpine, iodine containing drops and skin lotion, local anaesthetics or systemic anaesthetics. Acetazolamide, sulpha drugs, analgesics and antibiotics Family History Many ocular disorders have a strong genetic background, which becomes more pertinent in cases of consanguinity among parents, e.g. errors of refraction, squint, glaucoma, cataract, dystrophies, abiotrophies, diabetic retinopathy and hypertensive retinopathy. Infective disease, both acute and chronic, may inflict members of a family or society— trachoma, acute epidemic conjunctivitis, tuberculosis and sometimes leprosy. Some maternal infections are passed to the child, e.g. rubella, syphilis, gonorrhoea and AIDS. Occupation Some occupations pose a threat to vision, e.g. blast furnace workers, glass blowers and people employed in the drug industry. People working on lathe machines are prone to foreign bodies in the eye, both intraocular and extraocular. Personal History Smoking and drinking may lead to chronic retrobulbar neuritis and toxic amblyopia.  CHAPTER 2 E XAMINATION OF V ISION AND R ECORDING OF V ISUAL ACUITY From Chapter 1 it is obvious that ocular symptoms outnumber non-ocular symptoms. Out of ocular symptoms, visual complaints are far more common than non-visual symp- toms. Hence, evaluation of visual status of a patient is of extreme importance in the clinical examination of an eye. Visual evaluation should get priority over the rest of the examination; this should be first, followed by others. The visual evaluation comprises the following: A. Distant vision B. Near vision C. Colour vision D. Field of vision E. Night vision In a given patient all of these need not be subnormal, various combinations are possible in the same patient and same eye. ➤ Recording of vision is not only of diagnostic, therapeutic and prognostic value, it has tremendous legal value that should not be overlooked in clinical ophthalmology There are individual variations in recording of vision. Each ophthalmologist has his/her own style and follows a particular school of training. It is customary to record distant and near vision in the following order. Vision without glasses is noted in the right eye first and then the left, followed by both the eyes together. Binocular vision is better than uniocular vision which was recorded separately, unless one eye is not fixing, may be amblyopic, or blind. Recording of vision with glasses is followed by examination without glasses in the same order. Next step, one should find out if the glasses used are for distance, near, or both, their type and power. Most widely used method to examine distant vision is to use Snellen’s chart (Fig. 2.1) in the language of the literate patient. For illiterate persons various types of modification like E chart (Fig. 2.2), Landolt’s broken C (Fig. 2.3), Allen picture chart (Fig. 2.4), and dots are available. Landolt’s C and E charts are most accurate, they are better than alphabets of Snellen’s charts. STYCAR (Snellen’s test for young children and retarded, Figs 2.5 and 2.6) is used for children. The charts are generally used at a distance of 6 m or 20 ft from the patient and kept straight.  EXAMINATION OF VISION AND RECORDING OF VISUAL ACUITY 15 Snellen’s charts consist of clearly inscribed black letters on white background. There are 28 letters arranged in seven rows. First line has a single and largest letter, seventh has the smallest letters. Size of the letters gradually diminishes in a ratio of 10 : 6 : 4 : 3 : 2 : 1.5 : 1, i.e. the topmost letter is 10 times larger than the letters in seventh row. The number of letters increases as size diminishes in successive lines. 60 H A L E 36 60 T N C E E 24 36 O L H A E E E 18 24 E C T N O E E E E E 12 18 9 C L O H N A E E E E 12 6 A E L O H C T E E E E E E 9 5 H T N E L A C O E 6 E E E E E E 4 A E C O H N T L Fig. 2.1 | Snellen’s chart. Fig. 2.2 | E test types. c c c c c c c c c c c c c c c c c c c c c c c c c c c c Fig. 2.3 | C chart. Fig. 2.4 | Allen pictures. 16 CLINICAL OPHTHALMOLOGY The charts are of two types: 1. Self-illuminated rotatory drums, which can be revolved round either a vertical or a horizontal axis manually or electrically. The panels of these drums are actually fitted in rectangular boxes and are translucent 2. Letters written on opaque white boards that are externally illuminated H LX V T A U V A C H T X 0 T X U L T O H H C A X O L Fig. 2.5 | STYCAR (Snellen’s test for young children and retarded) chart (left) to be used at 6 m. Small card (right) to be held by child to point out to the matching letter. F N P R Z 60 metres 200 1-0 (feet ) 48 (160) E Z H P V 0.9 38 (125) D P N F R 0.8 30 (100) R D F U V 0.7 24 (80 ) U R Z V H 0.6 19 (63 ) H N D R U 0.5 15 (50) Z V U D N 0.4 12 (40) V P H D E 0.3 9.5 (32) P V E HR 0.2 7.5 ( 25) E H V D F 0.1 6 ( 20) N U Z F E Log MAR 0 4. 0 :161 U H N Z R 3 0 ( 12.8 ) D N E F P 3. 0 ( 10 ) P U E P I Fig. 2.6 | Minimal angle of resolution in minute is MAR. Bailey–Lovie Log MAR chart for distant and near vision.  EXAMINATION OF VISION AND RECORDING OF VISUAL ACUITY 17 If there is shortage of space, then instead of 6 m, 3 m distance is used with changed position of drum in relation to the patient. The patient sits under a reversed chart and looks at a plain mirror in front, fixed at a distance of 3 m. As the patient looks into the mirror he gets a virtual, erect, laterally reversed view of the chart that seems to be at 6 m of distance. In still smaller places two plane mirrors and one usual chart is used with suitable adjustment of mirrors. A proportionately reduced smaller distance chart is also available, which is good for home visits, non-ambulatory patients, school surveys and mass screening. As rays arising from 3 m are slightly divergent, a person may use accommodation or may move a little forward resulting in wrong assessment of vision, especially in children. Letters of the Snellen’s chart can be projected on a suitable screen as well. Method of Recording of Vision The patient sits comfortably in front of a vision drum kept at 6 m away in a nor- mally illuminated room. The right eye is tested first. The other eye is occluded com- pletely without exerting pressure on the globe. Various methods of occlusion are given below: 1. Occluder 2. Hand-held occluder 3. Palm of the patient In children, it is better to close the eye with the palm of the examiner. Otherwise they try to peek over the occluder. Trial frame (Fig. 2.7): These are spectacle frames in which lenses and other optical devices like occluder, pin hole, stenopeic slit, Maddox rod and prisms can be put and removed at ease. They have an adjustable nose bridge and a pair of sidebars. The rims are open on the upper side and have slots for multiple devices. The fronts of the rims have axis of cylinder etched on their faces. The numbering is done according to uni- versal convention where zero is marked on temporal side of right eye and nasal side of left eye, 180⬚ on nasal side of right eye and temporal side of left eye, 90⬚ is vertically down in mid position. The axis is marked at an interval of 5⬚, which is sufficient for usual clinical work. The trial frame should be light and well fitted with provision to adjust intrapupillary distance. They are generally available in two sizes, adult and child. They may also be hand held or fixed to a headband. A very sophisticated trial frame is incorporated in refraction unit. 0 Rt 180 0 Lt 180 45 135 45 135 90 90 Fig. 2.7 | Notation in a trial frame. 18 CLINICAL OPHTHALMOLOGY CONSTRUCTION OF LETTERS IN SNELLEN’S CHART Vision denotes the smallest retinal image, which can be appreciated correctly at a given distance. This depends upon the intensity of light, spectrum of light and distance. Area of retina-stimulated plays a very important part in visual acuity. Vision is maxi- mum at the fovea and falls sharply at the periphery. Vision on the retinal periphery is one-tenth of foveal vision in the normal eye, and that is why a patient with a small macular lesion may not be able to read more than two lines on a Snellen’s chart, while a patient with extensive peripheral lesions and unaffected macula may have very good vision. It is customary to state that parallel rays form a pinpoint image on the macula to give good vision. In clinical practice it is presumed that a pencil of rays form a minute circle of clear vision, called circle of least diffusion. The larger the circle of least diffusion, the poorer the vision. Diameter of an ideal circle of least diffusion is 0.04 mm. This forms the basis of construction of the Snellen’s chart. In a typical Snellen’s chart, the letters are so constructed that one line of each letter forms a square, which forms an angle of 5 min on the fovea at a specific distance. For example the top letter forms an angle of 5 min at a distance of 6 m; this angle will enlarge if the letter is moved nearer to the patient, and diminish if it is moved away, making it blurred (Figs 2.8–2.10). Each square is divided into 25 smaller squares of equal size. Each square forms an angle of 1 min on the fovea. An angle less than 1 min which is equal to 0.04 mm, is not visible to the eye. This is the diameter of ideal circle of blur or minimal separable distance that can be differentiated by fovea. ➤ One degree ⴝ 1/360th of a circle. 1/60 degree ⴝ 1 min ➤ Thus each arm of a letter should form an angle of 1 min to be visible at a given distance 5 min 5 min 1 min 1 min 1 min Fig. 2.8 | Construction of Snellen’s letter and Landolt’s ring. 6/36 6/26 6/12 H C E Fig. 2.9 | H, C and E subtend an angle of 5 min at 36, 24 and 12 m, respectively.  EXAMINATION OF VISION AND RECORDING OF VISUAL ACUITY 19 E E E 12 m 24 m 36 m Fig. 2.10 | Letter of same size when brought nearer subtends larger angle. In MAR chart (Fig. 2.6), optotypes of subsequent lines differ by a logarithmic differ- ence. The charts are larger than usual Snellen’s chart and are used at 4 m. In Snellen’s chart, the size of the letters (optotypes) changes by half octave after 6/36 and is noted as 6/60, 6/36, 6/24 and 6/18, etc. If a person cannot see the top letter, following options are available: 1. Increase the size of the letter till it becomes visible 2. Reduce the distance between the chart and the patient The first option is not practical. However with letters projected on a screen in place of the usual charts, the size of a letter may be changed at will. The second option is used to record vision if the top letter is not visible. HOW TO RECORD LEVEL OF DISTANT VISION Vision is recorded as a fraction in which the denominator denotes the distance at which the letter should be visible and the numerator indicates distant at which the let- ter is visible. The top letter in a standard vision chart should be visible at a distance of 60 m in a normal eye. If it is visible at 6 m it is written as 6/60, similarly 6/36 means that the letter that should be visible at 36 m is visible at 6 m. The same fraction can be written as 6/60 ⫽ 1/10 ⫽ 0.1 or 20/200, where 200 stands for distance in feet. A normal eye should be able to read the seventh line at a distance of 6 m and it should be written as 6/6. If the patient cannot make out the top letter at 6 m on a standard chart, the patient is moved by 1 m at a time until the top letter becomes clear. If it is visible at 5 m it is noted as 5/60, at 4 m as 4/60 and then 3/60, 2/60 and 1/60, respectively, as the patient is moved by 1 m at a time. A patient with 5/60 vision may be able to read the second or third line, i.e. he can read 6/36 or 6/24 line, if moved by 1 m towards the chart, e.g. 4 m from it. It will be inappropriate to write 5/60 as 4/36 or 4/24. If the patient cannot see the top letter at a distance of 1 m then attempts to record vision on the vision chart are given up and the patient is asked to count fingers of the examiner at various distances. This is noted as FC or finger counting. The distance at which the patient can count fingers is noted. For example, counting fingers at a distance 20 CLINICAL OPHTHALMOLOGY of half a meter is noted as FC half meter. A single finger count may be guesswork by the patient. At least three accurate counts should be taken as correct. Finger count can be roughly translated into Snellen’s factor, since thickness of the adult finger is almost the same as that of a single line of the top letter. A patient with 6/60 vision should be able to count fingers at a distance of 6 m. Therefore 6/60 ⫽ FC 6M, 5/60 ⫽ FC 5M, 1/60 ⫽ FC 1M roughly. If the patient is unable to count fingers at 1 m, the examiner moves his palm in front of the eye and asks if the patient can see something moving. If a patient appre- ciates the movement of the hand, it is noted as hand movement and recorded as HM. While eliciting the ability to count fingers or ability to appreciate movement of the hand, the examiner’s finger or hand is used as an object and not the patient’s; even a blind person can say if his own hand is moving or not. If a patient’s vision is less than hand movement, his ability to perceive light is tested and recorded as perception of light (PL). How to Test Perception of Light To test PL one eye is completely closed so that no light reaches it. Light is then flashed in the uncovered eye and the patient is asked if he can sense this light. If the patient fails to do so, vision is recorded as no perception of light or NO PL. While recording the vision of a person, it is the maximum vision present that should be noted, e.g. a patient, who can read the top letter from 6 m (6/60) will surely be able to do so from 5 and 4 m. The patient will have FC, as well as HM, but it should be noted as 6/60 and not as 6/60 with CF, hand movement and PL. Absence of light per- ception should be recorded as NO PL and not blind. ➤ Perception of light is the ability to perceive light anywhere on the retina. It is not a macular function test. A patient may have an extensively scared macula but will retain perception, while other macular functions may be absent or faulty Causes of loss of perception of light Causes are total disruption of optic nerve, trans-section of optic nerve, avulsion of optic nerve, primary, secondary and glaucomatous optic atrophy, central retinal artery occlusion, extensive retinal lesion and total retinal detachment. ➤ Any amount of opacity of media may it be corneal, lenticular or vitreous with intact retina and optic nerve will not produce loss of perception of light. Perception of light once lost is lost forever Projection of Light So far the methods employed were used for recording central vision. It has already been noted that peripheral vision is less than central or foveal vision. However, in the  EXAMINATION OF VISION AND RECORDING OF VISUAL ACUITY 21 presence of a good central vision, the periphery may be extensively defective and vice versa. It is of extreme importance that both peripheral and central vision be noted for complete evaluation of visual status of an eye. ➤ Projection of light denotes gross retinal function at the periphery ➤ Central vision denotes function of cones ➤ Peripheral vision shows function of rods How to Examine Projection of Light Projection of light is the ability to perceive light at the retinal periphery. To examine the projection of light, the patient is asked to look straight and the other eye is closed. A small beam of light is thrown from various directions. The patient is asked to state the direction of light, the direction is noted down, projection of light is recorded as PR and the direction is noted along with it. Presence of projection of light is denoted as ⫹ and absence as ⫺. For example PR ⫹ ⫹ ⫹ ⫹ means projection from all quadrant, PR ⫹ ⫹ means projection from two quadrants. The quadrant in which projection is present is noted as superior, lateral, inferior and medial. When the patient can see light coming from the temporal side his nasal retina is stimulated and tested, similarly if the patient can see light from the nasal side then his temporal retina is stimulated and tested. It is generally believed that projection should be tested only when vision is reduced to perception of light and not with any other level of vision. In case of retinal detachment of lower part, the patient may have 6/36 or better vision with faulty projection infe- riorly. Similarly a patient with advanced chronic simple glaucoma may have HM and faulty projection. Hence, it should be a routine practice to test projection of light with every level of visual acuity noted. Causes of faulty projection are: 1. Retinal detachment 2. Long-standing glaucoma 3. Advanced retinal dystrophy 4. Central artery obstruction 5. Post-papilledematous optic atrophy Points to Remember in Recording Distant Vision 1 First examine the right eye 2. Close the left eye while testing right eye 3. Record maximum vision 4. If there is no perception, write it as NO PL and not as blind 5. Test projection with every level of vision 6. Repeat it in the left eye 7. Record vision in both eyes together 8. Take every possible care while recording vision in eyes of children, as they may memorise Snellen’s Chart, see through the other eye or peek over the occluder 22 CLINICAL OPHTHALMOLOGY Method of Documenting Distant Vision Vision in the right eye is preceded by the abbreviation RE and left by LE. If abbrevi- ation RE and LE are not inscribed then vision appearing on the left side of the paper or on the top is taken as belonging to the right eye, e.g. 1. RE 6/60 LE 6/36 or 6/60 6/36 2. RE 6/60 6/60 LE 6/36 6/36 Vision in both eyes together is preceded by the abbreviation BE. The other method is using letters OD, OS and OU standing for RE, LE and BE, respectively. Letters OD mean oculus dexter, OS mean oculus sinister, and OU mean oculus uterque or unitas. Recording of Near Vision In a normally illuminated room, the patient is given a near vision chart of Snellen’s or Jaeger’s to read at his normal working distance. Though near vision is tested in both eyes simultaneously, the more scientific method would be to test it in the two eyes sep- arately. While testing near vision, distant vision should be tested first it as there may be difference in vision in the two eyes. In presbyopic age, a patient with uniocular myopia uses the myopic eye for near and the emmetropic or hypermetropic eye for distance and does not require a near correction. The near vision charts may have letters rather than sentences, dots, Landolt’s broken C or E to read. The size of the letters gradually reduces from bottom towards top. They are designated between 5 and 48, each prefixed by the letter N or J depending on the type of chart used, e.g. N5, N6, etc. Causes of diminished near vision Commonest cause of diminished near vision is presbyopia followed by uncorrected facultative hypermetropia and aphakia. If the patient uses glasses for near vision, power of glasses should also be recorded. Examination of Spectacles of the Patient After recording the distant vision attention should be directed towards the patient’s spectacle or spectacles. Each pair of spectacles should be examined to find out if it is for distance, near or for both. Is it bifocal, unifocal, multi-focal or progressive? While examining spectacles the patient should be asked if he/she is using any other magnifier for near as well as distant vision, e.g. low vision aids or contact lenses. The next step is to find out the type and power of the lenses in the patient’s spectacles. Procedure to examine spectacles (Plates 2.1 and 2.2) 1. Hold the spectacle by the frame and not by the lens 2. The lenses should be very close to the eyes of the examiner 3. Look at a distant object  EXAMINATION OF VISION AND RECORDING OF VISUAL ACUITY 23 Plate 2.1 | Correct method to find out type and power of a given glass. Hold the glass very near the eye and see shape, size and movement of a distant object. Plate 2.2 | Wrong method. Holding glasses away from the eye and looking at a near object. 4. Move the lenses from side to side, up and down and rotate to note the movement and the size of the object and any distortion Spectacle Lenses A lens is an optical device, which has at least one curved surface. Optical lenses are of two types: 1. Convex or converging lenses 2. Concave or diverging lenses Divergence is also known as negative convergence. For calculation and reconstruction of images the rays are always presumed to travel from left to right. Those lenses in which parallel rays are brought to focus on the right side of the lens are plus or converging lenses, while those in which rays come to focus on the left-hand side of the lens are divergent or negative lenses. 24 CLINICAL OPHTHALMOLOGY Biconvex Plano-convex Concavo-convex Biconcave Plano-concave Convexo-concave Fig. 2.11 | Types of lenses. Fig. 2.12 | Movement of image in a plus sphere. Based on shape lenses can be plano-convex or plano-concave, when one surface is plane and other surface is convex or concave, respectively. It could be biconvex or biconcave. It could be concavo-convex or convexo-concave; the last word denoting the type of lenses (Fig. 2.11). A lens can be spherical, cylindrical or sphero-cylinder. The first two can either be plus or minus sphere or plus and minus cylinder. Sphero-cylinders are those lenses that have both spherical and cylindrical components. They could be of the same type, e.g. plus sphere with plus-cylinder or minus-sphere with minus-cylinder; these are called com- pound sphero-cylinder. The next combination is the combination of sphere and cylinder of opposite signs and they are called mixed sphero-cylinders, where the value of the cylin- der is always more than that of the sphere and opposite in sign. To find out the type of lens, it should be held between the thumb and index finger by the edge and not the substance and is kept as near as possible to the eye of the exam- iner. A distant object is seen through the lens. The lens is then moved by the following three movements: 1. Move side to side 2. Move up and down 3. Rotate between thumb and index finger 4. Do not focus a near object 5. Do not move the lens in anterio-posterior direction These rules are applicable for spectacle lenses also. Characteristics of plus sphere (Fig. 2.12 and Table 2.1) 1. The image moves opposite to the direction of movement of the lens, i.e. if the lens is moved to the right, the image moves to the left  EXAMINATION OF VISION AND RECORDING OF VISUAL ACUITY 25 2. Movement is equal in all directions 3. There is no distortion of the image on rotating the lens 4. There is magnification of the image 5. Thickness of the lens is maximum at the centre Characteristics of minus sphere 1. The image moves in the direction (Table 2.1) of the lens, i.e. if the lens moves to the right the image also moves towards the right 2. The movement is equal in all directions 3. There is no distortion of the image on rotation of the lens 4. There is minification of the image 5. Thickness of the lens is minimum at the centre A spherical lens is part of a sphere, hence it has equal power in all meridians and parallel rays are brought to a pinpoint on the focal point. A cylindrical lens is part of a cylinder, it has power in one meridian and parallel rays are brought to focus as a line at the focal plane. Characteristics of a plus cylinder 1. The image moves against in one direction 2. There is no movement at right angles to this meridian 3. The image is elongated at right angles to the axis and shortened in the direction of the axis 4. When the cylinder is rotated, there is distortion of image (Fig. 2.13) Characteristics of a minus cylinder 1. The image moves with one direction 2. There is no movement at right angles to this meridian 3. The image is elongated along the axis of the cylinder and shortened at right angles to the axis 4. When the cylinder is rotated, there is distortion of the image Table 2.1 Comparison between characteristics of plus and minus sphere (Fig. 2.13) Characteristics Plus (Convex) Minus (Concave) Movement of image Against With Distortion on rotation Nil Nil Size of image Magnified Minified Thickness of lens Maximum at the centre Minimum at the centre Edge of lens Thin Thick AV AH AH AV Fig. 2.13 | Changes in the size and shape of the image due to alignment of axis in plus cylinder. AH ⫽ hori- zontal axis; AV ⫽ vertical axis. 26 CLINICAL OPHTHALMOLOGY Method to Find Out Power of a Lens Hand neutralisation To neutralise a lens, the first step is to find out whether it is convex, concave or mixed lens. Next, find out whether it is a sphere, a cylinder or a sphero-cylinder. Start putting spherical lenses of the opposite sign very close to the lens and observe the movement of the image. Keep on adding lenses until one meridian is neutralised. In spherical lenses, a single sphere of the opposite sign neutralises all meridians. In cylindrical lenses, a sphere of the opposite sign will neutralise only one axis; the other axis will show opposite movement equal to the cylindrical value. To neutralise a plus one cylinder if a minus one sphere is used, it will neutralise the cylindrical value but will add an equal amount of cylindrical value of the opposite sign at right angles to the cylinder. It would be best to use a cylinder of the opposite sign and same power, in the same axis, to neutralise a cylinder. To neutralise a compound sphere, first neutralise the sphere with a sphere of the opposite sign and then add a cylinder of the opposite sign in the appropriate axis. A lensometer is an optical device that is used to find out the power of a lens. There are two types of lensometers: fully optical and computerised automatic. The optical lensometer consists of a small telescope mounted on a stand, which looks like a clinical microscope. The image of a target, which is in-built, is focussed by a standard lens. The unknown lens is now inserted in the system and the target is focussed again. The difference between these two readings gives the power of lens at particular axis. The instrument can also be used to find out: 1. Power of the sphere 2. Power of the cylinder 3. Axis of the cylinder 4. Optical centre of the lens 5. Value of the presbyopic addition Automated computerised lensometer The basic principle is the same as any other lensometer. This gives a quick and more accurate reading and digital print-out is also available. Power of an optical lens is measured in dioptre. This is a unit of measurement of converging power (positive or negative) of a lens. It is the reciprocal of focal length in metres. A lens of one diopter will have focal length of 1 m. The more the converging power of a lens, the less is its focal length (Table 2.2). Table 2.2 Relation between dioptre and focal length Dioptre Focal length (cm) 10 10 5 20 4 25 2 50 1 100 0.5 200  EXAMINATION OF VISION AND RECORDING OF VISUAL ACUITY 27 Table 2.3 Type of spectacle lens and their uses Type of lens Error of refraction Plus sphere Hypermetropia, presbyopia and aphakia Minus sphere Myopia Plus sphero-cylinder Compound hypermetropic astigmatism Minus sphero-cylinder Compound myopic astigmatism Single plus cylinder Simple hypermetropic astigmatism Single minus cylinder Simple myopic astigmatism Mixed sphero-cylinder Mixed astigmatism and pseudophakia Uses of lens in ophthalmology Lenses can be used either for therapeutic purposes, i.e. to improve subnormal vision or in an instrument used for diagnostic purposes. The former is in the form of spectacles, contact lenses, low vision aids or IOLs. The latter is in the form of instruments of routine and special investigation, e.g. ophthalmoscope, slit lamp, synaptophore, etc. (Table 2.3). Prisms Prisms are composed of two refractive surfaces that are inclined to each other. The line at which the two surfaces meet is called apex, while the surface opposite to apex is called base. The angle formed by two surfaces is called the refracting angle. Light pass- ing through a prism is deviated towards the base and broken into seven colours, i.e. VIBGYOR. As the emerging rays bend towards the base, the object seems to move towards the apex. Thus, if two prisms of equal strength are put base together and apex away, light will converge towards the base. If two prisms of the same strength are put apex together and base away, the rays will diverge. Thus, two prisms with base against each other will act as a convex lens and two prism with apex against each other will act as concave lens. This principle is the basis of optics of lenses. A lens is said to be a combination of multiple prisms. If two prisms of equal strength are kept base to apex, they will act as a plate of glass (Figs 2.14 and 2.15). Nomenclature of Prism For all practical purposes, strength of a prism is measured in prism dioptre. It denotes 1 cm displacement of an image towards the apex when the object is kept at a distance of 1 m from the prism. Identification of a Prism Identifying a single thick prism is not difficult as in single prism or prism bar. For optical purposes, the prisms used are thin and low powered, and most of them are incorporated into spectacle lenses or pasted on their surface, e.g. Fresnel prisms. To find out if a given lens has prismatic value or not, hold the lens in the same fash- ion as any other lens near the eye and look at a straight line at a distance. If a device has a prism, the image of the line will move towards the apex and parallel with the base. 28 CLINICAL OPHTHALMOLOGY O A O B A I B I B B O O Fig. 2.14 | Identification of prism. A ⫽ apex, BB ⫽ base, OO ⫽ object, I ⫽ image. (A) (B) Fig. 2.15 | Optics of (A) convex lens and (B) concave lens. Now rotate the prism by 90⬚, there will be no deviation of the image. Now add prisms base to apex till there is no shift in first position, this will neutralise the prism (Fig. 2.14). Uses of Prisms 1. Therapeutic uses: Prisms by themselves do not correct errors of refraction. They are used to relieve diplopia and relax or reinforce convergence. In muscle imbalance they are prescribed as base in, base up or down. The base may rarely be oblique. 2. The diagnostic instruments that contain prisms are: (a) Maddox double prism (b) Riddley’s rotating prism (c) Synaptophore (d) Direct ophthalmoscope (e) Indirect ophthalmoscope (f) Gonioscope (g) Microscope Types of Spectacle Lenses Toric lenses: These lenses are curved lenses and curvatures are different, different in meridians and in two surfaces. It is like a section through a teaspoon or an automobile tyre. One meridian is more curved than the other. The meridian at right angles to the steepest is flatter than the other meridians. Numerically lower value is called base curve. In toric lenses, meridians of maximum and minimum curvature are at right angles to each other. Toric lenses can be plus, minus or combination of both. They can be plano- cylindrical. Toric lenses produce least distortion (Fig. 2.16).  EXAMINATION OF VISION AND RECORDING OF VISUAL ACUITY 29 Fig. 2.16 | Torus. Fig. 2.17 | Myodisc. Fig. 2.18 | Lenticular lens. Fig. 2.19 | Aspherical lens. Meniscus: Front surface is more curved than back surface. Power in all meridians is the same. Myodisc: These are high myopic lenses where peripheral part is devoid of power, the peripheral surfaces are parallel, central 25–30 mm have corrective power. They are used to reduce the overall weight of the lens (Fig. 2.17). Lenticular: These are high plus lenses where central portion is thick and has correc- tive power while peripheral surfaces are parallel; it gives an appearance of bull’s eye (Fig. 2.18). Aspherical lenses: In an aspherical lens, the inner curve is circular and spherical. The outer curve is parabolic and aspherical (Fig. 2.19). Coloured Lenses White lenses (transparent) allow not only the visible spectrum of light between 380 and 760 nm but also some of ultraviolet, less than 360 nm and infrared, i.e. more than 760 nm to enter the eye. Some of the ultraviolet and infrared lights are absorbed by the lens. Both ultraviolet and infrared have harmful effects. Ultraviolet rays have ionising effect on ocular tissues, specially cornea, conjunctiva and lens. Infrared rays have a thermal effect. To avoid these effects of light, protective glasses are prescribed. Unfortunately these coloured glasses are worn more for cosmetic reason than thera- peutic value. Coloured or tinted glasses are also used to reduced glare in large pupils, e.g. myopia, mydriasis, coloboma of iris and albinism. Therapeutic effect of tinted glasses depends directly upon their ability to absorb ultraviolet and infrared part of the spectrum. Various types of tinted glasses are available. A good tinted glass should absorb all ultraviolet, and infrared, and 60–80% of visible light. These are made out of glass as well as plastic. They are of two types. One which has a tint that does not 30 CLINICAL OPHTHALMOLOGY change with illumination. These are the usual goggles used for cosmetic purpose. The second type of tint changes in intensity with varying illumination; brighter the light darker the tint. Darkening occurs very quickly but lightening takes sometime. They are known as photosun and photogrey. Special tinted glasses are prescribed in indus- trial workers, e.g. welders, steel furnace workers and glass blowers. EXAMINATION OF COLOUR VISION Colour vision is a property of cones. Rods have very little colour sense. Colour vision depends upon three factors; hue, saturation and intensity. Hue depends upon wave- length, saturation depends upon its proportion to white, and intensity is brightness. Hues are violet, blue, green, yellow, orange and red. Violet is nearer 380 nm while red is nearer to 760 nm. Colour blindness may be congenital or acquired. Congenital can be dichromatopsia which is common colour blindness or achromatopsia, a rare form with subnormal vision and nystagmus that is not seen in other types of colour blindness. Dichromatopsia (Partial colour blindness) The three subgroups of this type are as follows: Protanopia—Single-colour defect, confuse red with blue, green. Deuteranopia—Two-colour defect confuses blue and green with purple. Tritanopia—Confuses yellow and blue. Normal persons are called trichromats, while those with colour defects are called anomalous trichromats. They can recognise all bright and saturated colours and they will call a leaf green and a ripe tomato red, but will not be able to match colours of var- ious hues of red or blue. The different type of anomalous trichromats are protanom- alous, deuteranomalous and tritanomalous. ➤ Colour vision defect is not true blindness because it does not produce diminished vision. It may, however, be associated with defective vision Monochromatism is rare. Blue blindness is generally acquired. Why Should Colour Vision Defect Be Tested? Some jobs require the ability to differentiate between coloured signals, like pilots, locomotive drivers, electricians, weavers and artists. Dress designers also require good colour sense. In some of these jobs people are disqualified due to defective colour sense. It is better to screen colour defects in a child and let the child know about it to plan for the future and save from embarrassment and disappointment in later life. Acquired colour vision defect is seen in diseases of the macula and optic nerve. Immature cataract also interferes with normal colour vision. Various methods for testing colour visions are: (a) Pseudo isochromatic plates (Plates 2.3 and 2.4) (i) Ishihara plates  EXAMINATION OF VISION AND RECORDING OF VISUAL ACUITY 31 1 2 3 4 5 6 Plate 2.3 | Sample of Ishihara plate. Person with Person with Fig Normal person red-green total colour deficiency blindness 1 12 12 12 2 29 70 X 3 5 2 X 4 6 X X 5 7 X X 6 X 5 X The mark X shows that the plate cannot be read Plate 2.4 | Corresponding index of Ishihara plate. (ii) Hardy Rand Rittler plates (iii) Stilling plates (b) Farnsworth-Munsell: 100 hue test Farnsworth-Munsell: D-15 test (c) Edridge Green lantern (d) Nagel’s anomaloscope Ishihara plates—These are most commonly used devices. It is useful to detect red green defect but not for blue yellow defects. The plates are made up of dots of primary colours printed on background of similar dots of confusing colour. Primary coloured dots are 32 CLINICAL OPHTHALMOLOGY arranged in such a way that they form a number, which is visible to normal trichro- mats. The person with colour vision defects will read them as some other number. To test colour blindness the person is given an Ishihara plate to read and his answers are noted down, which are later matched with a list attached to the plate at the end and the type of colour vision defect is noted. Examination of the Visual Field When an eye fixes an object, it is not only the point of fixation that is visible but also a large area around the point of fixation. All the area that is visible at a given time around a point of fixation is the field of vision for that eye in that gaze. Visual field is restricted superiorly by the superior orbital rim, medially by the bridge of the nose and inferiorly by the maxilla. As there is no obstruction on the lateral side, hence this field is widest. Visual fields of the two eyes put together is larger than that of a single eye. Field of vision has been defined as—an island of vision in a sea of blindness. The peak of the island represents maximum visual acuity, i.e. fovea. The optic disc which has no vision acts as bottomless pit and represents, the blind spot. The visual field, besides patho- logical defects, depends upon the size of the object, the intensity of light and colour of the object. Coloured objects give less stimuli than a white object of the same size. The visual field examination gives the following information: 1. Location of lesion, e.g. retina, optic nerve, chiasma and optic tract and radiation 2. Congruence 3. Side 4. Homonymous/heteronymous Test object: Size of the test object is expressed in fractions. This represents the size of the object used to plot the contour in relation to distance at which test is per- formed. For example in a Lister perimeter that has a radius of 33 cm, the distance of eye from the target is 33 cm ⫽ 330 mm. If an object of 3 mm in diameter is used, the test object will be 3/330. These are also called test targets. The commonest colour is white, but they can be any colour. While recording field of vision the following should be noted—name of the patient, eye tested, vision in the eye, size of test object used, and distance and colour of the target. Size of the target varies between 1 and 50 mm. Various methods of testing visual field are: 1. Confrontation method 2. Amsler grid: For papillo-macular defect within 10⬚ 3. Perimeters: Arc perimeter and bowl perimeter. Perimeters are used mostly for peripheral field but central field can also be recorded 4. Tangent screen: For 30⬚ central field 5. Multiple pattern field analyser 6. Automated perimeters Confrontation method This is one of the most useful methods of charting both central as well as peripheral field of vision. It can also give information regarding colour field if tested with a coloured object like a small coloured medicine vial, small white and coloured pins etc.  EXAMINATION OF VISION AND RECORDING OF VISUAL ACUITY 33 The patient and the examiner sit face to face 1 m away from each other, the eyes of both are at the same level. To examine the right eye of the patient, the left eye is closed. The observer closes his right eye. The patient is asked to fix the left eye of the examiner. Now the observer moves his index finger of left hand from periphery to centre and the patient is asked to say yes as soon as the finger becomes visible. This is repeated all around. If the observer and patient’s area of visibility are same, the patient has normal field. The other method is to ask the patient to count fingers of the observer in different quadrants after the other eye has been closed. A medicine vial with a coloured cap can be used to give coloured field, when moved in the same fashion. The field changes shown on confrontation are gross and must be confirmed by other methods. Amsler grid (Fig. 2.20) This consists of a 10 cm ⫻ 10 cm square that is divided into 400 small squares, each 5 mm ⫻ 5 mm (Fig. 2.20A). The squares are printed on a dull background, the lines being generally white. Any graph paper will also serve the pur- pose. The outer square forms an angle of 20⬚ and each small square forms an angle of 1⬚. The chart is held 30 cm from the eye under usual indoor illumination. The presbyope should use reading glasses. When the chart is kept at a usual reading distance, it occupies the central 10⬚ of the field and the blind spot is outside the chart. Thus the chart can be used to locate field changes of 10⬚ round point of fixation, which is the geometrical cen- tre of the chart. The chart is used to plot central and centrocecal field defects, both absolute and relative and find out if there is any metamorphopsia. Thus, this can differentiate between optic neuropathy and maculopathy. Any defect on the periphery of the chart could be part of a larger field defect that should be tested and confirmed on the Bjerrum screen (Fig. 2.20E). How to use the Amsler grid: One eye is tested at a time, the other eye is closed. The patient keeps the chart at usual reading distance and fixes the central point. The patient is asked: 1. Can he see the central point? If the answer is no, the patient has an absolute central scotoma. The patient is then asked to state the extent of scotoma. He may be asked to draw it (Fig. 2.20B). A B C... D E F Fig. 2.20 | Interpretation of Amsler grid test. 34 CLINICAL OPHTHALMOLOGY 2. If he can see the central point, is it as clear as the surrounding area? If it is duller than the sur- rounding area, the patient has a relative scotoma (Fig. 2.20C) 3. Does the patient see blank spaces or holes away from the point of fixation? In this case, the patient has a paracentral scotoma (Fig. 2.20D) 4. Are all the corners of the grid intact or is one of the corners or side missing? The patient has a large scotoma that is extending beyond 10⬚ (Fig. 2.20E) 5. Are the lines are straight or wavy; a wavy outline means metamorphopsia (Fig. 2.20F) Tangent screen or bjerrum screen (Fig. 2.21) This inexpensive device can be fixed on a wall and does not require any electric supply or additional space. It is used to chart central field defect within 308 around the point of fixation. It can be made on a dull rigid cork or hard board. There is a prominent central point of fixation, and around this point of fixation are drawn inconspicuous concentric circles at a difference of 58. Six such circles are drawn so that the diameter of outer circle is 1m. There can be a screen twice this size where the outer diameter is 2m. The former is used at a dis- tance of 1m, the latter at a distance of 2m. Advantage of the large screen is that the scotomas are enlarged, hence are easily detected. Each circle is again divided by radial lines of 58 separation. The blind spots are marked on each side of point of fixation on the horizontal line that divides the circle into two equal upper and lower parts. The blind spot extends 58 horizontally and 88 vertically. It is vertically oval in shape. It lies between 138 and 188 horizontally. The test objects vary from 1 to 50 mm circular discs, generally white in colour and can be of different colours. The targets are mounted on one end of black, non-reflecting pointers. The patient sits at a distance of 1 m from the screen in front of it. The eye looks straight ahead and a