Transcript CORNEA
CORNEA ANATOMY & PHYSIOLOGY Three Coats of Eye Ball 1.OUTER COAT 2.MIDDLE COAT 3.INNER COAT Outer Coat Tough Fibrous Coat Post 5/6th of Globe White & Opaque Sclera Radius---12mm Outer Coat Tough Fibrous Coat Ant 1/6th of Globe Transparent Cornea Radius---8mm Corneoscleral Limbus Junction of Cornea and Sclera Contains 1.Trabecular Meshwork 2.Canal of Schlemn Size of Cornea Verticle-------10.6 mm Horizontal---11.7 mm Thickness Central portion----0.52 mm Peripheral portion----1 mm Structure Three Layers 1. Epithelium & its Basement 2. Stroma & its ant condensation ( Bowman Zone) 3.Endothelium & its Basement (Descemet Membrane) Layers of Cornea Structure From Anterior to Posterior 1. 2. 3. 4. 5. Epithelium Bowman Zone Stroma Descemet Membrane Endothelium Epithelium • 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 Epithelium • Surface cell layer • Wing cell layer • Basal cell layer • Basement membrane Stroma 90% of the corneal thickness • Bowman Zone • Lamellar Stroma Once deformed its typical structure is not restored Inner Lining • Descemet membrane (Regenerates) • Endothelium Single layer of cells Cells are tightly bound together Responsible for dehydration Never regenerates Blood supply • 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 Nerve Supply • 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 Cornea • 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 Transparency • 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 Signs of Corneal Disease 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 Signs of Corneal Disease Superficial 2.Punctate epithelial keratitis It is the hallmark of viral infections. • Swollen epithelial cells • Visible unstained • Stains with rose bengal Signs of Corneal Disease Superficial 3.Epithelial Oedema Sign of • Endothelial decompensation • Severe acute elevation of IOP Signs of Corneal Disease Superficial 4.Filaments Small coma shaped mucus strands lined with epithelium. One end attached with epithelium Signs of Corneal Disease Superficial 5.Pannus Inflammatory or degenerative ingrowth of fibro vascular tissue from limbus Signs of Corneal Disease Stromal Lesions 1.Infiltrates Focal areas of active stromal inflammation 2. Oedema Increased corneal thickness Decreased transparency 3. Vascularization Signs of Corneal Disease Lesions of Descemet Membrane 1. Breaks Corneal enlargement Keratoconus Birth trauma 2. Folds (Striate Keratopathy) Surgical trauma Ocular hypotony Stromal oedema PRINCIPLES OF MANAGEMENT OF CORNEAL DISEASE • • • 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 MICROBIAL KERATITIS ( Bacterial) • Ocular surface disease: Trauma, post-herpetic corneal disease, bullous keratopathy, corneal exposure, dry eye and diminished corneal sensation. • Contact lens wear MICROBIAL KERATITIS ( Bacterial) Pathogens which can produce corneal infection in intact epithelium. • 1.Neisseria gonorrhoeae • 2.Corynebacterium diphtheriae • 3.Listeria • 4.Haemophilus Staph. aureus and strep. pneumoniae • Oval, yellow-white, densely opaque stromal suppuration surrounded by relatively clear cornea Psuedomonas • Thick mucopurulent exudate, diffuse liquefactive necrosis and semi-opaque ground glass appearance of adjacent stroma Enterobacteriaceae • Shallow ulceration, grey-white pleomorphic suppuration and diffuse stromal opalescence. Endotoxins may induce ringshaped corneal infilterates MANAGEMENT • History • Clinical examination (including staining and sensitivity) • Hospitalization • Corneal scrapping • Treatment 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 750mg BD • Cycloplegics • Steroid therapy (controversial) • Corneal biopsy or excisional keratoplasty Poor response to treatment • Wrong diagnosis • Wrong treatment • Drug toxicity FUNGAL KERATITIS • Filamentous fungal keratitis –Aspergillus - Fusarium History of vegetable matter injury • Greyish-white ulcer with indistinct margins • Surrounded by feathery infilterates • Ring infilterate • Endothelial plaque • Hypopyon Candida keratitis • Usually develops in pre-existing corneal disease or immunocompromised patient • Yellow-white ulcer • Dense suppuration D/D of fungal keratitis • Suppurative bacterial keratitis • Herpetic stromal necrotic keratitis MANAGEMENT • Culture • Biopsy • Antifungal therapy – Initially broadspectrum econazole 1% topically – Then depending upon sensitivity natamycin or imidazole for 6 weeks • Systemic ketoconazole • Therapeutic penetrating keratoplasty ACANTHAMOEBA KERATITIS • Protozoan –active (trophozoite) –dormant (cystic) • Common in swimmers and CL wearers CLINICAL FEATURES • Blurred vision and disproportionate pain • Patchy anterior stromal infilterates • Perineural infilterates (radial keratoneuritis) • Infilterates coalesce –ring abcess, ulceration and hypopyon • White satellite lesions MANAGEMENT • Corneal scrappings stained with calcoflour white • Corneal biopsy • Treatment with chlorhexidine, polyhexamethylenebiguanide drops, dipropamidine and propamidine. • Therapeutic penetrating keratoplasty HERPES SIMPLEX KERATITIS Primary ocular herpes: - Blepharoconjunctivitis - Keatitis (punctate epithelial) DENDRITIC ULCER • 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 Differential diagnosis • Herpes zoster keratitis • Healing corneal abrasion • Pseudodendrites due to soft contact lens • Acanthamoeba keratitis • Drug toxicity TREATMENT • Antiviral therapy – Acycloguanosine 3% ointment – Trifluorothymidine 1% drops – Adenine arabinoside 3% ointment, 0.1% drops – Idoxuridine • Debridement (with sterile cottontipped bud 2mm beyond the edge of ulcer) OTHER ENTITIES • Stromal necrotic keratitis • Disciform keratitis PHLYCTENULOSIS • Predominantly affects children • Etiology – Tuberculosis – Delayed hypersensitivity reaction to staphylococcal or other bacterial antigen PRESENTATION • Photophobia, lacrimation and blepharospasm. SIGNS • Conjunctival: Pinkish-white nodule surrounded by hyperaemia • Corneal: May resolve spontaneously or extend radially to the cornea. May cause severe ulceration or perforation. TREATMENT • Short course of topical steroids • Topical antibiotics KERATOCONUS • Onset at puberty • Central or paracentral stromal thinning • Apical protrusion • Irregular astigmatism • Autosomal dominant transmission with incomplete penetrance proposed CLASSIFICATION • By keratometry: - Mild (< 48 D), - moderate (48-54 D) - severe (> 54 D) • By morphology: - Nipple cones – Oval cones – Globus cones Early signs • 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). LATE SIGNS • Decreased visual acuity • Munson sign • Fleischer ring • Corneal scarring • Acute hydrops Keratoglobus MANAGEMENT • Spectacle correction • Contact lenses • Penetrating keratoplasty