The eye is the The eye is the photosensory organphotosensory organ of the of the body.body.

It is composed of three tunics (coats):It is composed of three tunics (coats):

1.1. Fibrous coatFibrous coat ( (sclera and corneasclera and cornea) ) forming the tough outer coat.forming the tough outer coat.

2.2. Vascular coatVascular coat ( (choroid, ciliary body choroid, ciliary body and irisand iris) forming the pigmented and ) forming the pigmented and vascular middle layer.vascular middle layer.

3.3. Neural coatNeural coat ( (retinaretina), forming the ), forming the innermost layer.innermost layer.

The eye is the The eye is the photosensory organphotosensory organ of the of the body.body.

It is composed of three tunics (coats):It is composed of three tunics (coats):

1.1. Fibrous coatFibrous coat ( (sclera and corneasclera and cornea) ) forming the tough outer coat.forming the tough outer coat.

2.2. Vascular coatVascular coat ( (choroid, ciliary body choroid, ciliary body and irisand iris) forming the pigmented and ) forming the pigmented and vascular middle layer.vascular middle layer.

3.3. Neural coatNeural coat ( (retinaretina), forming the ), forming the innermost layer.innermost layer.

ScleraScleraScleraScleraTough white fibrous coat.Tough white fibrous coat.

Forms the posterior 5/6 of the eye ball.Forms the posterior 5/6 of the eye ball.

About 0.5 mm in thickness.About 0.5 mm in thickness.

Composed of flat bundles of collagen fibers Composed of flat bundles of collagen fibers running in directions parallel to the surface.running in directions parallel to the surface.

Functions:Functions:– Protection of the internal structures.Protection of the internal structures.– Maintains the shape of the eye.Maintains the shape of the eye.– Gives attachment to the extrinsic muscles.Gives attachment to the extrinsic muscles.

Tough white fibrous coat.Tough white fibrous coat.

Forms the posterior 5/6 of the eye ball.Forms the posterior 5/6 of the eye ball.

About 0.5 mm in thickness.About 0.5 mm in thickness.

Composed of flat bundles of collagen fibers Composed of flat bundles of collagen fibers running in directions parallel to the surface.running in directions parallel to the surface.

Functions:Functions:– Protection of the internal structures.Protection of the internal structures.– Maintains the shape of the eye.Maintains the shape of the eye.– Gives attachment to the extrinsic muscles.Gives attachment to the extrinsic muscles.

CorneaCorneaCorneaCorneaThe cornea is The cornea is transparenttransparent, , avascularavascular and and forms the anterior 1/6 of the eye ball.forms the anterior 1/6 of the eye ball.

Its is composed of Its is composed of five layersfive layers::

1.1. Corneal epithelium.Corneal epithelium.

2.2. Bowman’s membrane.Bowman’s membrane.

3.3. Stroma (substantia propria).Stroma (substantia propria).

4.4. Descemet’s membrane.Descemet’s membrane.

5.5. Corneal endothelium.Corneal endothelium.

The cornea is The cornea is transparenttransparent, , avascularavascular and and forms the anterior 1/6 of the eye ball.forms the anterior 1/6 of the eye ball.

Its is composed of Its is composed of five layersfive layers::

1.1. Corneal epithelium.Corneal epithelium.

2.2. Bowman’s membrane.Bowman’s membrane.

3.3. Stroma (substantia propria).Stroma (substantia propria).

4.4. Descemet’s membrane.Descemet’s membrane.

5.5. Corneal endothelium.Corneal endothelium.

Corneal epitheliumCorneal epitheliumCorneal epitheliumCorneal epitheliumStratified squamous non-keratinized. Stratified squamous non-keratinized. About five-cells thickness.About five-cells thickness.

The lateral membranes of the adjacent The lateral membranes of the adjacent cells are extensively interdigitated and cells are extensively interdigitated and joined by desmosomes.joined by desmosomes.

The epithelium has many free nerve The epithelium has many free nerve endings and is very sensitive to stimuli endings and is very sensitive to stimuli specially pain.specially pain.

Stratified squamous non-keratinized. Stratified squamous non-keratinized. About five-cells thickness.About five-cells thickness.

The lateral membranes of the adjacent The lateral membranes of the adjacent cells are extensively interdigitated and cells are extensively interdigitated and joined by desmosomes.joined by desmosomes.

The epithelium has many free nerve The epithelium has many free nerve endings and is very sensitive to stimuli endings and is very sensitive to stimuli specially pain.specially pain.

Bowman’s membraneBowman’s membraneBowman’s membraneBowman’s membraneA thin membrane below the corneal A thin membrane below the corneal epithelium.epithelium.

Appears homogenous on light Appears homogenous on light microscope.microscope.

With electron microscope, it appears to With electron microscope, it appears to be formed of type I collagen fibers be formed of type I collagen fibers arranged in random fashion.arranged in random fashion.

It is synthesized by the corneal It is synthesized by the corneal epithelial cells and underlying stroma.epithelial cells and underlying stroma.

A thin membrane below the corneal A thin membrane below the corneal epithelium.epithelium.

Appears homogenous on light Appears homogenous on light microscope.microscope.

With electron microscope, it appears to With electron microscope, it appears to be formed of type I collagen fibers be formed of type I collagen fibers arranged in random fashion.arranged in random fashion.

It is synthesized by the corneal It is synthesized by the corneal epithelial cells and underlying stroma.epithelial cells and underlying stroma.

Substantia propriaSubstantia propriaSubstantia propriaSubstantia propriaThe thickest layer of the cornea.The thickest layer of the cornea.Composed of type I collagen fibers Composed of type I collagen fibers and corneal cells (modified and corneal cells (modified fibroblasts).fibroblasts).The fibers are arranged in lamellae The fibers are arranged in lamellae which run parallel to the corneal which run parallel to the corneal surface.surface.The matrix consists of sulfated The matrix consists of sulfated proteoglycans rich in chondroitin proteoglycans rich in chondroitin sulfate and keratin sulfate.sulfate and keratin sulfate.

The thickest layer of the cornea.The thickest layer of the cornea.Composed of type I collagen fibers Composed of type I collagen fibers and corneal cells (modified and corneal cells (modified fibroblasts).fibroblasts).The fibers are arranged in lamellae The fibers are arranged in lamellae which run parallel to the corneal which run parallel to the corneal surface.surface.The matrix consists of sulfated The matrix consists of sulfated proteoglycans rich in chondroitin proteoglycans rich in chondroitin sulfate and keratin sulfate.sulfate and keratin sulfate.

Descemet’s membraneDescemet’s membraneDescemet’s membraneDescemet’s membraneIt is a thin membrane containing It is a thin membrane containing an atypical type of collagen an atypical type of collagen fibers which have elastic fibers which have elastic character.character.

It is considered as the It is considered as the basement membrane of the basement membrane of the corneal endothelium.corneal endothelium.

It is a thin membrane containing It is a thin membrane containing an atypical type of collagen an atypical type of collagen fibers which have elastic fibers which have elastic character.character.

It is considered as the It is considered as the basement membrane of the basement membrane of the corneal endothelium.corneal endothelium.

Corneal endotheliumCorneal endotheliumCorneal endotheliumCorneal endotheliumIt is the innermost layer of the It is the innermost layer of the cornea.cornea.Composed of a single layer of Composed of a single layer of large hexagonal squamous large hexagonal squamous cells.cells.This layer is involved in This layer is involved in transport of materials from the transport of materials from the anterior chamber.anterior chamber.

It is the innermost layer of the It is the innermost layer of the cornea.cornea.Composed of a single layer of Composed of a single layer of large hexagonal squamous large hexagonal squamous cells.cells.This layer is involved in This layer is involved in transport of materials from the transport of materials from the anterior chamber.anterior chamber.

The cornea is The cornea is avascularavascular, it derived its , it derived its nutrition from the aqueous humour and the nutrition from the aqueous humour and the blood vessels of the surrounding limbus.blood vessels of the surrounding limbus.Corneal epithelial cells divide repeatedly by Corneal epithelial cells divide repeatedly by mitotic division, but the endothelial cells do mitotic division, but the endothelial cells do not divide after birth the are not replaced.not divide after birth the are not replaced.The transparency of the corneaThe transparency of the cornea is due to: is due to:

1.1. Its uniform diameter.Its uniform diameter.2.2. Regular arrangement of the collagen Regular arrangement of the collagen

fibers.fibers.3.3. Properties of ground substance (matrix).Properties of ground substance (matrix).4.4. Absence of blood vessels.Absence of blood vessels.5.5. Ion pumps of the corneal endothelial cells Ion pumps of the corneal endothelial cells

maintains a critical fluid level within the maintains a critical fluid level within the substantia propria.substantia propria.

The cornea is The cornea is avascularavascular, it derived its , it derived its nutrition from the aqueous humour and the nutrition from the aqueous humour and the blood vessels of the surrounding limbus.blood vessels of the surrounding limbus.Corneal epithelial cells divide repeatedly by Corneal epithelial cells divide repeatedly by mitotic division, but the endothelial cells do mitotic division, but the endothelial cells do not divide after birth the are not replaced.not divide after birth the are not replaced.The transparency of the corneaThe transparency of the cornea is due to: is due to:

1.1. Its uniform diameter.Its uniform diameter.2.2. Regular arrangement of the collagen Regular arrangement of the collagen

fibers.fibers.3.3. Properties of ground substance (matrix).Properties of ground substance (matrix).4.4. Absence of blood vessels.Absence of blood vessels.5.5. Ion pumps of the corneal endothelial cells Ion pumps of the corneal endothelial cells

maintains a critical fluid level within the maintains a critical fluid level within the substantia propria.substantia propria.

Vascular (uveal) layerVascular (uveal) layerVascular (uveal) layerVascular (uveal) layerIt is the It is the middle layermiddle layer of the eye. of the eye.Highly vascularHighly vascular layer. layer.Composed of Composed of three componentsthree components: : choroid, choroid, ciliary body and irisciliary body and iris..Choroid provides nutrition for the retina and Choroid provides nutrition for the retina and absorbs the light which has passed through it.absorbs the light which has passed through it.Ciliary muscles contract to change the Ciliary muscles contract to change the convexity of the lens.convexity of the lens.Ciliary body is responsible for secretion of Ciliary body is responsible for secretion of aqueous humour.aqueous humour.The Iris control the amount of light entering The Iris control the amount of light entering the eye by the dilator and sphincter pupillae the eye by the dilator and sphincter pupillae muscles.muscles.

It is the It is the middle layermiddle layer of the eye. of the eye.Highly vascularHighly vascular layer. layer.Composed of Composed of three componentsthree components: : choroid, choroid, ciliary body and irisciliary body and iris..Choroid provides nutrition for the retina and Choroid provides nutrition for the retina and absorbs the light which has passed through it.absorbs the light which has passed through it.Ciliary muscles contract to change the Ciliary muscles contract to change the convexity of the lens.convexity of the lens.Ciliary body is responsible for secretion of Ciliary body is responsible for secretion of aqueous humour.aqueous humour.The Iris control the amount of light entering The Iris control the amount of light entering the eye by the dilator and sphincter pupillae the eye by the dilator and sphincter pupillae muscles.muscles.

RetinaRetinaRetinaRetinaIt is the innermost layer of the eye.It is the innermost layer of the eye.Is a delicate sheet of nervous tissue that Is a delicate sheet of nervous tissue that forms the photoreceptor of the eye.forms the photoreceptor of the eye.Anteriorly, it decreases in thickness and Anteriorly, it decreases in thickness and becomes continuous with the ciliary body becomes continuous with the ciliary body and called ora serrata.and called ora serrata.Posteriorly, it forms the optic disc, where the Posteriorly, it forms the optic disc, where the nerve fibers merge to form the optic nerve.nerve fibers merge to form the optic nerve.FoveaFovea lies in the center of the retina and lies lies in the center of the retina and lies on the visual axis and represent the area of on the visual axis and represent the area of the maximum focus and visual acuity.the maximum focus and visual acuity.The retina is formed of 10 histological layers.The retina is formed of 10 histological layers.

It is the innermost layer of the eye.It is the innermost layer of the eye.Is a delicate sheet of nervous tissue that Is a delicate sheet of nervous tissue that forms the photoreceptor of the eye.forms the photoreceptor of the eye.Anteriorly, it decreases in thickness and Anteriorly, it decreases in thickness and becomes continuous with the ciliary body becomes continuous with the ciliary body and called ora serrata.and called ora serrata.Posteriorly, it forms the optic disc, where the Posteriorly, it forms the optic disc, where the nerve fibers merge to form the optic nerve.nerve fibers merge to form the optic nerve.FoveaFovea lies in the center of the retina and lies lies in the center of the retina and lies on the visual axis and represent the area of on the visual axis and represent the area of the maximum focus and visual acuity.the maximum focus and visual acuity.The retina is formed of 10 histological layers.The retina is formed of 10 histological layers.

Layers of the RetinaLayers of the RetinaLayers of the RetinaLayers of the Retina1.1. Pigment epithelium.Pigment epithelium.2.2. Rods and cones.Rods and cones.3.3. Outer limiting membrane.Outer limiting membrane.4.4. Outer nuclear layer.Outer nuclear layer.5.5. Outer plexiform layer.Outer plexiform layer.6.6. Inner nuclear layer.Inner nuclear layer.7.7. Inner plexiform layer.Inner plexiform layer.8.8. Ganglion cell layer.Ganglion cell layer.9.9. Nerve fibers (optic nerve) layer.Nerve fibers (optic nerve) layer.10.10. Inner limiting membrane.Inner limiting membrane.

1.1. Pigment epithelium.Pigment epithelium.2.2. Rods and cones.Rods and cones.3.3. Outer limiting membrane.Outer limiting membrane.4.4. Outer nuclear layer.Outer nuclear layer.5.5. Outer plexiform layer.Outer plexiform layer.6.6. Inner nuclear layer.Inner nuclear layer.7.7. Inner plexiform layer.Inner plexiform layer.8.8. Ganglion cell layer.Ganglion cell layer.9.9. Nerve fibers (optic nerve) layer.Nerve fibers (optic nerve) layer.10.10. Inner limiting membrane.Inner limiting membrane.

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