cornea

1. Slide 1: Introduction - Title: Cornea - cornea is a transperant,avascular, watch glass like structure.it forms anterior one sixth of the outer fibrous coat of the eye ball Slide 2 Anatomy of the cornea - Title: Dimensions of the Cornea - Anterior surface: elliptical - Posterior surface: circular - Thickness: 0.5-0.6 mm (center), 1-1.2 mm (periphery) - Refractive index: 1.376 - Refractive power: 45 dioptres (three-fourth of the total refractive power of the eye. Slide 4: Histology - Title: Histology of the Cornea - 6 layers: epithelium, Bowman's membrane, substantia propria (corneal stroma), pre-Descemet's membrane (Dua's layer), Descemet's membrane, endothelium - Image: Diagram showing the 6 layers Slide 5: Epithelium - Title: Epithelium - Outermost layer - Stratified squamous non-keratinized epithelial cells - It consists of 5-6 layers of cells - Tight junctions between superficial epithelial cells prevent penetration of tear fluid in stroma. Slide 6: Bowman's Membrane - Title: Bowman's Membrane - This layer is consists of acellular mass of condensed collagen fibrils. - 12 µm in thickness - Binds corneal stroma to the basement membrane of epithelium. - it shows resistant to infection, but once destroyed it is unable to regenerate and therefore it heals by scarring . Slide 7: Stroma (Substantia Propria) - Title: Stroma (Substantia Propria) - 0.5 mm in thickness (90% of total thickness) - It consists of Collagen fibrils embedded in hydrated matrix of

2. proteoglycans. - Lamellae arranged in many layers, alternating at right angles to eachother and to the plane of cornea. - Becomes continuous with scleral lamellae at the limbus Slide 8: Pre-Descemet's Membrane - Title: Pre-Descemet's Membrane (Dua's Layer - Discovered in 2013 by Dr. Harminder Dua. - Located anterior to Descemet's membrane. - 15 micrometer thick acellular structure. - Strong and impermeable to air. Slide 9: Descemet's Membrane - Title: Descemet's Membrane - It is Strong homogenous basement membrane of corneal endothelium which is Separated from stroma by Pre-Descemet's membrane - Resistant to chemical agents, trauma, and pathological processes - Can regenerate - Consists of collagen and glycoproteins. Slide 10: Endothelium - Title: Endothelium - it consists of Single layer of flat polygonal epithelial cells - it Appears as a mosaic on slit-lamp examination. - Best examined with specular microscope - Cell density: 3000 cells/mm2 in young adults - Decreases with age, compensated by enlargement (polymegathism) and migration. - endothelial cells contain Active-pump mechanism which keeps cornea dehydrated . ..Nerve supply -long Ciliary nerves