Corneal diseases.pdf

Block 2.1 (2024-2025) CORNEAL DISEASES Done by : Dhuha AlBjais. Zainab Moayad Objectives § Basic anatomy of the cornea § Corneal defence mechanisms § Keratitis: definition, causes § Herpetic eye disese –Keratitis: clinica picture & management ...

Block 2.1 (2024-2025) CORNEAL DISEASES Done by : Dhuha AlBjais. Zainab Moayad Objectives § Basic anatomy of the cornea § Corneal defence mechanisms § Keratitis: definition, causes § Herpetic eye disese –Keratitis: clinica picture & management  The cornea and sclera are composed of The refractive power of the eye is 60 collagen, however, the cornea is diopters, cornea has 2/3 which is 40 transparent, why? Bc the Arrangement diopters , on the other hand, the lens takes of collagen fibres (collagen type 2). 20 diopters which is represented with 1/3. Cornea Cornea derived from the greek word (Kerato) ; horn or shield. It is the most important refractive media in the eye The formula to calculate diopters is: D=1/focal length in meters. It is the transparent tissue in the front of the globe through which light passes into the eye. through which light passes into the eye, where the sharp vision can be formed and then sent to the optic nerve and finally to the brain.  very very important slide. Embryology oThe corneal epithelium is a derivative of surface ectoderm located proximal to the developing lens. oThe corneal stroma and endothelium, along with the anterior segment, are derived from neural crest cells. oThe mature, transparent cornea is ultimately formed when the mesenchymal-derived stromal keratocytes produce organized collagen matrix. The cornea is of two origins: the anterior part is formed by ectoderm the posterior part is formed from neural crest cells. Embryogenesis of the cornea limbus is an important structure cause it contains a stem cells Cornea & Limbus Anatomy Dimension & thickness Cornea is divided into central and Central thickness , peripheral peripheral. Mature cornea Histology & physiology Cornea is covered by epithelium, which is capable of fast regeneration with stem cells located at the Limbus. Bowman’s layer, located beneath epithelium, it is acellular layer Develops scarring whenever it is damaged, If scarring develops in the visual axis or central cornea, vision is impaired. The corneal stroma is made of collagen fibers type 2 produced by Keratocytes and comprises 75% of the corneal thickness. Continue Descemet’s membrane: the strongest layer of the cornea. it consists of collagen fiber type 4, on which grows endothelium. Endothelium Opposite Endothelium: to epithelium, there is monolayer of hexagonal cells no regeneration. non- regenerating cells maintains corneal transparency (actively transport fluid from stroma into the anterior chamber) be formed of 5 layers ; 1- Epithelium. 2-Bowman layer. 3-Stroma. 4-Descemet membrane. 5-Endothelium. Continue ‫ بالسفينة التي تحتوي على‬cornea ‫شبه الدكتور عمل ال‬ ‫ثقوب وطاقم السفينة في عمل دائم الخراج الماء منها كالية‬.gap junctions ‫عمل ال‬ ‫مثال بعد السباحة في مسبح تكون الرؤية ضبابية خصوصا‬.‫حول االضواء بعدها بفترة من الوقت ترجع الرؤية طبيعية‬ Active fluid pumping: This movement of water is necessary to maintain a transparent cornea. Damage to the endothelium from injury, inflammation, or high intraocular pressure results in corneal edema. the function of endothelium: 1- covers the lens (protection). 2-takes the aqueous humor out of the cornea.  -Combination of mechanical, anatomical, and immunological defense mechanisms : Eyelids, Reflexive blinking. Protective Tear film: Flushing effect of tear fluid, immune Mechanisms of mediated cells & lysozyme. the Cornea Epithelium: Hydrophobic property form a diffusion barrier, regenerate quickly & completely. Subepithelial nerve plexus , highly sensitive  Keratitis: Most common type of eye pathology (Kerat-) means cornea (-it is) means inflammatory Keratitis isinflammationof thecornea It may involve single or multiple layers Types: infectious or non-infectious (inflammatory process). Infectious means there is infection, non-infectious due to chemical injury or autoimmune or traumatic. There are 4 forms of infectious keratitis, include bacterial, Viral , fungal andparasitickeratitis.  Is there condition we lose the sensation of cornea? First, the nerve that is related to pain sensation is ophthalmic branch of trigeminal nerve Second, lose of sensation is due to either congenital causes or acquired causes like post surgery, Ocular pain, (Rarely absent, examples…?) post trauma, trigeminal ganglion, nfections like (herpes) - Note optic nerve is sensory in which it conduct light signals ( Irritation Not pain) med211 Redness (injection) Tearing (epiphora) Keratitis symptoms Clear, watery Purulent secretion (discharge) Not clear, it could be The symptoms for patients with kertatitis: -pain and it is rarely absent, when could the pain be absent? Photosensitivity (photophobiua) yellow and green ( +Photophobia indicating bacterial), Whrn there is nerve damage. Impaired vision. whitish (viral or allergy) The nerve supply for cornea trigerminal nerve the ophthalmic branch, so if there is any damage to the trigerminal ganglion (due to trauma, malignancy etc..) the patient would present with painless inflammation of cornea Irritation -Redness (injection) in the conjunctiva covering the sclera ( not the sclera bc it is avascular) so any inflammation,dryness it will cause dilation of these blood vessels and appears as redness  The clinical signs are many some of them are specific of some types and other less specific dendritic ulcer ulcer and it’s less Hypopial inside the defined eye ( ‫) مثل الفص‬ viral parasitic Fungal Bacterial Infectious Keratitis with Different Etiologies Each one of these appearances are sign of suggestive of specific type of karatitis  First the clinical diagnosis. Second we take sample with the help of slit lamp ( microscope ). Third culture and sensitive test. Doing culture can help us to know the organism First patient will be on topical anesthesia culture and sensitivity test will be useful with bacteria and fungi because they will grow there. Keratitis is an emergent disorder that can lead to irreversible vision loss if left untreated. Diagnosis of infectious Diagnosis is usually based on history & clinical findings onslit- lampexamination; however, culture of the organism is mandatory & keratitis confirmatory. most sensitive less sensitive There are many types of herpes viruse but in ophthalmology we are concerned with two types 1-simplex 2 -zoster Simplex is two types 1 : above the diaphragm infections 2 : below the diaphragm infections But there’s isolated cases of types 2 in the eye HSV is a double-stranded DNA virus that causes disease after direct contact with skin or mucous membranes Herpes Virus by virus-laden secretions from an infected host. HSV &HZV Once in the tissue, the virus spreads from the site of the initial infection to the neuronal cell bodies, where it can lie dormant for similarity of HSV & HZV : years until reactivation occurs. 1- both of them from the same group of viruses. 2- both of them have primary infection and secondary reactivation The differences: 1- in HSV : the first attack will produce rash 2- in HZV : the first attack will produce chicken box Herpes Virus It has been found that almost 90% percent of people worldwide over the age of 60 harbor HSV. HSV &HZV Primary infection is in childhood The two most common forms of HSV are HSV-1 & HSV-2. HSV-2 commonly present with genital infections, though crossover does occur.  The first infection come from mucus debris or secretions in the eye, then it will go to the ophthalmic branch then to the trigerminal ganglion, and stay there Dormant Reactivation of Herpetic infection  Herpes simplex keratitis Infection due to reactivatedherpes simplex virusHSV- 1from the trigeminalganglion Clinical features + lid swelling Usuallyunilateralredness, eyepain, Foreign body sensation, Photophobia & Blurry vision Can lead to vision loss if untreated Skin rash , vesicles may present This can come after a period of prodrome, so what does prodrome mean? The symptoms that proceed the clinical picture In herpes simplex and with many other viruses the patient would have flu-like symptoms ( myoalgia, generalised body aches, fever) then the clinical picture would be obvious Diagnostics Good history by making sure about any previous attacks Slit-lampexamination and fluorescein staining Fluorescein staining:superficial corneal erosions in the shape of branching ulcer(dendriticulcers) that resemble the branches of a treewith terminal bulb Direct fluoresceinantibodytest (HSV antigen detection) orpolymerase chain reaction(PCR) test If the picture is not clear clinically and I would to make sure it herpes simplex , we do PCR  If the patient is immunocompromised, old age. Having repeated attacks, we use oral Or of the patient is scared to use something on their eyes. if HSV affects the epithelial will use typical treatment , but if it affects on the deep tissue and reache the stroma we will use systemic. Treatment for Epithelial HSV Keratitis: Topical Antiviral gel or ointments like trifluridine or ganciclovir Oral antiviral (e.g.,acyclovir)when topical treatment cannot be administered by the patient, or refractory cases despite topical treatment Steroids should not be used in initial treatment of dendriticepithelial keratitis. Steroids will make the virus more active, and for the ulcer, much bigger  Difference depends on the rash: HSV 1 rash mostly around the mouth HSV 2 rash mostly around genitalia HZV vascular eruption will be localized in Specific Herpes zoster keratitis dermatome, med211 Etiology:reactivatedHZV (VZV) Clinical features: Prodrome: headache , malaise , fever Impaired vision, eye pain, &irritation (foreign body sensation), Photophobia Vesicular eruption& anesthesia in theinnervation atophthalmic nerve (V1) area (forehead, bridge and tip of the nose) Very uniquely, it respects the midline, the end of the innervation Terminal bulbs are absent  Herpes zoster keratitis Diagnosis Slit-lampexamination and fluorescein staining Small dendritic lesions on the corneal surface without terminal bulb Treatment:Topical and oralantiviral treatment : acyclovir , valacyclovir or famciclovir. Prognosis treated early ——> ulcer and scarring are small and not affects the vision Children’s treatment will be different because the vision in children is still developing so that we will start with oral treatment to prevent any abnormalities in development that lead to vision defect If the cornea affected severely, we could ‫ ﻦﻴﻌﻟا ﻞﺴﻛ‬such as amblyopia do corneal transplant On the other hand, there is a chance of recurrent Also, the patient will use topical steroid ( risk factor of recurrence ) Med211 Quiz Q1/Regeneration dose not occur Q2/In embryologic life the corneal in which of the following: epithelium is formed by which of the following: A. Endothelium. B. Epithelium. A. Neural crest. C. Stroma. B. collagen matrix D.Bowman layer. C. Ectoderm. D. Endoderm. Q3/All of the following are Q4/In the diagnosis of keratitis, which of considered predisposing factor of the following is correct? F21 keratitis, EXCEPT F21 A.Based on history taking only A.Diabetes B.Identification of the pathogen is crucial by B.Contact lens microbiological examination C.Logphthalmos C.Not necessary painful D.Hydrophobic epithelium D.Corneal sensation is intact in herpes zoster keratitis 4/B 2/C 3/D 1/A Answers Good Luck !