1 OUTER COAT 2 MIDDLE COAT 3 INNER
- Slides: 65
1. OUTER COAT 2. MIDDLE COAT 3. INNER COAT *
Tough Fibrous Coat Post 5/6 th of Globe White & Opaque Sclera Radius---12 mm *
Tough Fibrous Coat Ant 1/6 th of Globe Transparent Cornea Radius---8 mm *
Junction of Cornea and Sclera Contains 1. Trabecular Meshwork 2. Canal of Schlemn *
Verticle-------10. 6 mm Horizontal---11. 7 mm Thickness Central portion----0. 52 mm Peripheral portion----1 mm *
Three Layers 1. Epithelium & its Basement 2. Stroma & its ant condensation ( Bowman Zone) 3. Endothelium & its Basement (Descemet Membrane) *
From Anterior to Posterior 1. Epithelium 2. Bowman Zone 3. Stroma 4. Descemet Membrane 5. Endothelium *
*50 -60 µm thick *Covers the stroma anteriorly *Continuous with epithelium of conjunctiva *Life of epithelial cells is 7 days *Prevent aqueous solutions to penetrate *
*Surface cell layer *Wing cell layer *Basal cell layer *Basement membrane *
90% of the corneal thickness *Bowman Zone *Lamellar Stroma Once deformed its typical structure is not restored *
*Descemet membrane (Regenerates) *Endothelium Single layer of cells Cells are tightly bound together Responsible for dehydration * Never regenerates
*Central cornea is avascular *Corneoscleral limbus is generously supplied by anterior conjuntival branches of the anterior ciliary arteries *Aqueous humor and tear film provides nutrients *
*Branches of the ophthalmic division of trigeminal nerve and are solely sensory *Most are concentrated in the anterior stroma beneath the Bowman zone and send branches forward into epithelium *Descemet membrane and * endothelium are not innervated
*The microvilli of the anterior surface of the squamous cell layer are wet by the mucin of tear film *These cells are joined by tight junctions that exclude water soluble substances *
*Tight junctions of the epithelial cells *Endothelial pump mechanism *Absence of blood vessels *Absence of pigments *Scarcity of cell nuclei in stroma *Regular structure of stroma *
Superficial 1. Punctate epithelial erosions Tiny , slightly depressed, epithelial defects which stain with flourescein but not with rose Bengal PEE are non specific and may develop in a wide variety of keratopathies *
Superficial 2. Punctate epithelial keratitis It is the hallmark of viral infections. *Swollen epithelial cells *Visible unstained *Stains with rose bengal *
Superficial 3. Epithelial Oedema Sign of *Endothelial decompensation *Severe acute elevation of IOP *
Superficial 4. Filaments Small coma shaped mucus strands lined with epithelium. One end attached with epithelium *
Superficial 5. Pannus Inflammatory or degenerative ingrowth of fibro vascular tissue from limbus *
Stromal Lesions 1. Infiltrates Focal areas of active stromal inflammation 2. Oedema Increased corneal thickness Decreased transparency 3. Vascularization *
Lesions of Descemet Membrane 1. Breaks Corneal enlargement Keratoconus Birth trauma 2. Folds (Striate Keratopathy) Surgical trauma Ocular hypotony Stromal oedema *
* * * Control of infection Control of inflammation Promotion of re-epithelialization – lubrication – lid closure – bandage soft contact lens *Prevention of perforation – tissue adhesive glue – conjunctival flap – systemic immunosuppressive agents * Corneal grafting *
*Ocular surface disease: Trauma, post-herpetic corneal disease, bullous keratopathy, corneal exposure, dry eye and diminished corneal sensation. *Contact lens wear *
Pathogens which can produce corneal infection in intact epithelium. *1. Neisseria gonorrhoeae *2. Corynebacterium diphtheriae *3. Listeria *4. Haemophilus *
*Oval, yellow-white, densely opaque stromal suppuration surrounded by relatively clear cornea *
*Thick mucopurulent exudate, diffuse liquefactive necrosis and semi-opaque ground glass appearance of adjacent stroma *
*Shallow ulceration, grey-white pleomorphic suppuration and diffuse stromal opalescence. Endotoxins may induce ring-shaped corneal infilterates *
*History *Clinical examination (including staining and sensitivity) *Hospitalization *Corneal scrapping *Treatment *
*Topical antibiotics – combination therapy with fortified amino glycoside and fortified cephalosporin or monotherapy with fluoroquinolone. Initial instillation at hourly intervals. *Subconjunctival injections *Systemic ciprofloxacin 750 mg BD *
*Cycloplegics *Steroid therapy (controversial) *Corneal biopsy or excisional keratoplasty
*Wrong diagnosis *Wrong treatment *Drug toxicity *
*Filamentous fungal keratitis - Fusarium * –Aspergillus
*Greyish-white ulcer with indistinct margins *Surrounded by feathery infilterates *Ring infilterate *Endothelial plaque *Hypopyon *
*Usually develops in pre-existing corneal disease or immunocompromised patient *Yellow-white ulcer *Dense suppuration *
*Suppurative bacterial keratitis *Herpetic stromal necrotic keratitis *
*Culture *Biopsy *Antifungal therapy – Initially broad- spectrum econazole 1% topically – Then depending upon sensitivity natamycin or imidazole for 6 weeks *Systemic ketoconazole *Therapeutic penetrating keratoplasty *
*Protozoan – active (trophozoite) dormant (cystic) *Common in swimmers and CL wearers * –
*Blurred vision and disproportionate pain *Patchy anterior stromal infilterates *Perineural infilterates (radial keratoneuritis) *Infilterates coalesce –ring abcess, ulceration and hypopyon *White satellite lesions *
*Corneal scrappings stained with calcoflour white *Corneal biopsy *Treatment with chlorhexidine, polyhexamethylenebiguanide drops, dipropamidine and propamidine. *Therapeutic penetrating keratoplasty *
* Primary ocular herpes: - Blepharoconjunctivitis - Keatitis (punctate epithelial)
*Opaque cells arranged in a course punctate or stellate pattern *Central desquamation leads to a linear branching ulcer. –Fluorescein stain – Rose Bengal stain –Diminished corneal sensitivity *Anterior stromal infilterates *Geographical or amoeboid ulcer *
*Herpes zoster keratitis *Healing corneal abrasion *Pseudodendrites due to soft contact lens *Acanthamoeba keratitis *Drug toxicity *
*Antiviral therapy – Acycloguanosine 3% ointment – Trifluorothymidine 1% drops – Adenine arabinoside 3% ointment, 0. 1% drops – Idoxuridine *Debridement (with sterile cotton- tipped bud 2 mm beyond the edge of ulcer) *
*Stromal necrotic keratitis *Disciform keratitis *
*Predominantly affects children *Etiology Tuberculosis – Delayed hypersensitivity reaction to staphylococcal or other bacterial antigen * –
*Photophobia, lacrimation and blepharospasm. *
*Conjunctival: Pinkish-white nodule surrounded by hyperaemia *Corneal: May resolve spontaneously or extend radially to the cornea. May cause severe ulceration or perforation. *
*Short course of topical steroids *Topical antibiotics *
*Onset at puberty *Central or paracentral stromal thinning *Apical protrusion *Irregular astigmatism *Autosomal dominant transmission with incomplete penetrance proposed *
*By keratometry: Mild (< 48 D), moderate (48 -54 D) severe (> 54 D) *By morphology: – Oval – Globus Nipple cones *
*Ophthalmoscopy: Oil droplet reflex *Retinoscopy: Irregular scissor reflex *Keratometry: Irregular astigmatism (principal meridians no longer 90 degree apart and mires cannot be superimposed) *Placido disc: Irregular reflected ring *Slit-lamp: Very fine deep stromal striae (Vogt lines). *
* *Decreased visual acuity *Munson sign *Fleischer ring *Corneal scarring *Acute hydrops
*Spectacle correction *Contact lenses *Penetrating keratoplasty *
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