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HISTOLOGY OF EYE

Dr Iram Tassaduq

EPITHELIUM Stratified

squamous non keratinized

Consist of 5-6 layer

Active mitosis Turnover time

for cells is 6-7 days

Extremely sensitive to touch

BOWMANS MEMBRANE Consists of collagen

fibers Acellular clear

membrane lie under the epithelium

Cannot be regenerated if destroyed

Provides strength to cornea

Acts as a barrier against spread of infections

CORNEAL STROMA Many layers of

collagen bundles run parallel to each other and parallel to the surface of the cornea making the cornea transparent,

Avascular structure Nuclei of fibroblasts 90% of corneal

thickness

DESCEMENTS MEMBRANE Fine

collagenous filaments

5-10 micrometer thick

Regenerates quickly

ENDOTHELIUM

Single layer of flat hexagonal cells with no mitosis

Pumps water out Prevent corneal

edema opacification

Maintain corneal transparency

LENS Capsule Refractile and formed of

type IV collagen Sub capsular

epithelium Single layer of cuboidal

epithelium present on anterior surface

Lens fibers Highly differentiated

cells.

LENS FIBERS Form the body of the lens.

located deep to the subcapsular epithelium.

Nucleated in the soft, outer cortex of the lens. As new lens fibers are added to the periphery of the cortex, lens fibers located deeper in the cortex loose their nuclei .

Cytoplasm filled with crystalline proteins. These proteins are responsible for the transparency .

RETINA Innermost layer of eye ball Develops from double walled optic cup Outer layer forms pigment epithelium Inner layer forms neural retina

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RETINA The retina is the site of sensory

transduction The retina is nervous tissue composed of

6 major types of neurons and one special type of glial-like cell (the Muller cell) 

The organization of the retina is based on a three neuron chain (photoreceptor cell to bipolar cell to ganglion cell)

MAJOR RETINAL CELLSRODS Thin elongated cells Composed of inner and outer segments 120 million photoreceptor cells called

rods (responsible for peripheral and dim light vision)

Contain rhodopsin

MAJOR RETINAL CELLSCONES Lesser in number than rods Responsible for providing central, bright

light, fine detail, and color vision Contain visual pigment iodopsin

MAJOR RETINAL CELLS Horizontal cells -

interconnect groups of photoreceptor cells

Bipolar cells - interconnect photoreceptor cells with ganglion cells

Amacrine cells interconnect groups of ganglion cells and bipolar cells

Ganglion cells possess long axons that extend through the nerve fiber layer of the retina and then come together to form the optic nerve 17

LAYERS OF RETINA Pigment epithelium The layer of rods and cones External limiting membrane. The outer nuclear layer Outer plexiform layer Inner nuclear layer. The internal plexiform layer Ganglion cell layer. Layer of optic nerve fibers The internal limiting membrane

PIGMENT EPITHELIUM Consist of columnar

cells Absorbs light Synthesizes

melanin granules Vitamin A

metabolism Cells have

phagocytic properties

LAYER OF RODS AND CONES

EXTERNAL LIMITING MEMBRANE Not a true

membrane Formed of row of

zonula adherens between muller cells and rods and cones

OUTER NUCLEAR LAYER

OUTER PLEXIFORM LAYER Formed by the

processes of photoreceptor cells and retinal neuronal cells that is horizontal, bipolar and amacrine cells

INNER NUCLEAR LAYER Consist of

nuclei of bipolar, amacrine,

horizontal and muller cells

INTERNAL PLEXIFORM LAYER

Formed of complex intermingled nerve cell processes

GANGLION CELL LAYER Consist of cell

bodies of large multipolar neurons

OPTIC NERVE LAYER Consist of axons of

ganglion cells

INTERNAL L+-IMITING MEMBRANE