Histology of cornea and retina
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  • 2. Organ of vision  Spherical in shape  Has 3 Coats i) Fibrous coat: Sclera & Cornea ii) Vascular coat: Choroid, ciliary body & Iris iii) Nervous coat: Retina  EYE
  • 3. CORNEA
  • 4. It is located in front of the eye and is continouous with the sclera at the limbus.  It is transparent  Avascular  Thickness: 1mm  Layers: (Superficial to deep) i) Corneal epithelium ii) Bowman’s membrane iii) Corneal stroma iv) Descemet’s membrane v) Endothelium  CORNEA
  • 6. 1.Corneal epithelium: Made of str.squamous non-keratinised Epithelium. - Extremely sensitive
  • 7. 2. BOWMAN’S MEMBRANE Also called as “Anterior limiting membrane”  It is about 10-12µm thick  Homogeneous lamina consisting of randomly oriented thin fibrils of collagen.  Synthesized by both corneal epithelium and underlying stroma.  Acts as a barrier to the spread of infection.  It can’t regenerate if damaged. 
  • 8. 3. CORNEAL STROMA It constitutes the bulk of the stroma (90% of thickness)  Type 1 collagen fibres arranged in many layers  Collagen fibres are highly ordered. 
  • 9. CANAL OF SCHLEMM - Is present at the sclero-corneal junction (limbus). - It is the site of outflow of Aqueous humor from the anterior chamber into the venous system
  • 10. 4. DESCEMET’S MEMBRANE Also known as ‘’Posterior limiting membrane’’  Acellular, homogeneous basement membrane consisting of interwoven network of collagen fibrils.  Derived from endothelium. 
  • 11. 5. ENDOTHELIUM Consists of single layer of squamous or low cuboidal cells on the posterior surface of cornea.  Functions: - Metabolic exchange - Synthesis of proteins - Reabsorption of excessive fluid 
  • 12.  SCLERA: It is a tough fibrous connective tissue layer. It consists of irregularly arranged dense tissue (Type I collagen fibers) connective  CHOROID: It is a thin, highly vascular layer that lies between sclera and retina. Layers: i) Supra choroid layer – fine collagen fibers, elastic fibers and pigment cells ii) Vascular layer – Large blood vessels iii) Chorio-capillary layer – Capillary network essential for nutrition of retina iv) Bruch’s membrane - A thin refractile membrane that seperates choroid from retina
  • 13. CILIARY BODY: - Consists of ciliary muscle (smooth muscle) and ciliary process. - Ciliary muscles alter the shape of lens for near and far vision. - Ciliary epithelium produces aqueous humour IRIS: lens - It arises from ciliary body and lies between cornea and - It has smooth muscle fibers, melanocytes and blood vessels Smooth muscles: Dilator pupillae and sphincter pupillae - Acts as diaphragm which controls amount of light entering the eye
  • 14.  LENS: It is a transparent, flexible, biconvex disc.  Consists of i) Lens capsule – Made up of type IV collagen and proteoglycans ii) Anterior epithelium – simple cuboidal epithelium iii) Lens substance – Anterior epithelial cells towards the equator become columnar in shape to form lens fibers. 
  • 15. RETINA
  • 16. RETINA Inner coat of the eyeball  Lines the posterior 3/4th surface  Contains photoreceptors (Rods & Cones) which are essential for vision  MACULA:(Fovea centralis) Part of retina where vision is most acute. Contains only cones BLIND SPOT: The point where optic nerve leaves the eye. No photoreceptors 
  • 17. LAYERS OF RETINA - Pigment epithelium - Layer of Rods & Cones - Outer Nuclear layer - Outer plexiform layer - Inner nuclear layer - Inner plexiform layer - Ganglion cell layer - Nerve fiber layer
  • 18. PIGMENT EPITHELIUM Outermost layer of retina which is seperated from choroid by Bruch’s membrane.  Consists of low cuboidal cells which contain melanin granules.  Melanin pigment absorbs light, thus prevents its reflection from outer coats of eye. 
  • 19. LAYER OF ROD AND CONE CELL PROCESSES  ROD – Processes are cylindrical  CONE – Processes are thicker and cone shaped.  This layer is photoreceptor in function.
  • 20. OUTER NUCLEAR LAYER Consists of nuclei belonging to rods and cones.  Nuclei are arranged in several layers.  This layer is thickly stained  Presence of pink linear marking called as outer limiting membrane or lamina. This results because of zonula adherens of the glial cells (Muller cells) with cellbodies of Photoreceptor. 
  • 21. OUTER PLEXIFORM LAYER This layer stains lightly  Contains synapses between rods and cones with the dendritic processes of bipolar cells and horizontal cells. 
  • 22. INNER NUCLEAR LAYER It consists of cell bodies and nuclei of bipolar cells, horizontal cells, amacrine cells and Muller’s cells  Bipolar cells – oriented perpendicular to the layers of retina  Horizontal cells – oriented parallel to the layers of retina  Amacrine cells – synaptic contact with axonal processes of bipolar cells in inner plexiform layers 
  • 23. INNER PLEXIFORM LAYER In this layer axons of bipolar cells synapse with dendrites of ganglion cells and amacrine cells
  • 24. GANGLION CELL LAYER Mainly consists of body and nuclei of large multipolar neurons (Ganglion cells)  They receive input from bipolar cells and their axons form optic nerve 
  • 25. NERVE FIBER LAYER It consists of central processes of ganglion cells, which gather together at the optic papillae (disc) and leave the eye as optic nerve.  Soon after leaving eye ball, it becomes myelinated  Blood vessels of retina are present only in the nerve fiber layer. 
  • 28. GLAUCOMA Failure of drainage of aqueous humour from the anterior chamber of eye, leads to prolonged increase in intraocular pressure. This condition is known as glaucoma.  An important cause of blindness 
  • 30. RETINAL DETACHMENT  As the apical ends of rods and cones are not firmly attached to the pigment epithelium, the retina may get separated from pigment epithelium. This condition is called detachment of retina.
  • 31. THANK YOU