Eye lect1.html usha kannan

EYE BALL

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INTRODUCTION

• The Eye is the organ of vision.

• Composed of :1. Eyeball.2. The adnexa.

Eyeball

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The Eyeball• Equator :an imaginary line about

the eyeball, which is the equidistant from the poles.

• Meridian: is one of many lines

passing from pole to pole that intersects the equator at right angles.

– Optic nerve :leaves the eyeball slightly ventral to the posterior pole

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Terminology of the eye• Cornea : the transparent

part of the eyeball .• Anterior pole: the highest

point on cornea .• Posterior pole : the

highest point on posterior surface .

• Optic axis: the straight line passing through both poles

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Eyeball The three tunics are:I- An external fibrous tunic-Cornea and Sclera.

II- A middle vascular tunic-Choroid coat,Cilliary body (cilliary muscle and cilliary process) and Iris.

III- An internal nervous tunic-Retina.

The fibrous tunic• The cornea forms

about one quarter of the fibrous tunic and bulges forward. It is composed off dense connective tissue arranged in lamellar form .

• The cornea doesn’t contain blood vessels; nutrients for its cells permeate from vessels in the limbus or are carried to it its surface in the lacrimal fluid and aqueous humor . 10

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The vascular Tunic (uvea)2) The ciliary body : toward the limbus the choroids

thickness to form it. 3) The Iris: the smallest part of the

vascular tunic, which extends from the cornea to the lens.

• It attached to sclera and ciliary body by pectinate ligament.

• the opening in the center is the pulpi

The internal tunic

• The internal tunic of the eyeball contains the light-sensitive receptor cells (known as retina). – It’s an extension of the

brain to which remains connected by the optic nerve.

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Anatomy of the Eye• 1. *The conjunctiva is a

clear membrane covering the white of the eye (sclera).

• The sclera is the postreior five-sixth of the outer coat. 

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• 3. *The cornea is a clear, transparent portion of the outer coat of the eyeball through which light passes to the lens. 

• 4. *The aqueous humor is a clear, watery solution in the anterior and posterior chambers.

• 5. *The iris gives our eyes color and it functions like the aperture on a camera, enlarging in dim light and contracting in bright light. The aperture itself is known as the pupil. 

6. *The pupil is the opening, or aperture, of the iris. 

• 7. *The anterior chamber is the area bounded in front by the cornea and in back by the lens, and filled with aqueous. 

• 8. *The lens helps to focus light on the retina

• 9. *The vitreous humor is a transparent, colorless mass of soft, gelatinous material filling the eyeball behind the lens. 

• 10. *The retina is the innermost coat of the back of the eye, formed of light-sensitive nerve endings that carry the visual impulse to the optic nerve. The retina may be compared to the film of a camera. 

• 11. *The choroid, which carries blood vessels, is the inner coat between the sclera and the retina. 

• 12. *The optic nerve conducts visual impulses to the brain from the retina.

• 13. *The artery is the vessel supplying blood to the eye. 

14. *The canal of Schlemm is the passageway for the aqueous fluid to leave the eye. 

• 15. *The ciliary body is an unseen part of the iris, and these together with the ora serrata form the uveal tract. 

• 16. *The macula is a small area in the retina that provides our most central, acute vision

• 17. *The ora serrata and the ciliary body form the uveal tract, an unseen part of the iris. 

• 18. *The posterior chamber is the area behind the iris, but in front of the lens, that is filled with aqueous

• 19. *The rectus medialis is one of the six muscles of the eye. 

• 20. *The vein is the vessel that carries blood away from the eye. 

• Optic disc:• Is a white spot medial and

superior to the posterior pole of the eye ball

• 1.5mm in diameter.

• Devoid of rods and cones.

• Blind spot.• Central artery of Retina enters

the eye through optic disc.

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• Macula lutea:• Is an yellowish area at

the posterior pole of the eye , about 3mm lateral to the Optic disc.

• 3mm-horizontally,• 1mm-vertically.• The Macula presents a

central depression –Fovea centralis, the bottom -Foveola o.4mm in diameter.

• Only cones are present .

Production of Aqueous Humor and Intraocular pressure

1. Ciliary Process:Produces Aqueous Humor

2. Posterior Chamber:Aqueous Humor flows from this chamber through thepupil in Anterior Chamber

3. Canal of SchlemmReabsorbs Aqueous Humor

Glaucoma:Increase in intraocular pressure due to build up ofAqueous Humor

Opthalmoscopic view of the retina showing the location of the Macula to the Optic Disc

Visual Pathway

1. Cones2. Bipolar neurons3. Ganglion cell’s axon forms the optic nerve4. Optic nerve to the Optic Chiasm5. Optic tract6. Lateral geniculate nuclei of the thalamus7. Optic Radiations8. Primary visual areas of the occipital lobes

Abnormalities ofThe Eye:1. Myopic -

nearsighted2. Hypermetropic -

Farsighted3. Presbyopia -

age-related failure of lens to accommodate

4. Astigmatism - Distorted vision due to irregular-shaped lens orcornea

5. Color Blindness - genetic defect that causes dysfunction of cones

Hemianopsia or hemianopia is visual field loss on the left or right

side of the vertical midline. It can affect one eye but usually affects

both eyes. Homonymous hemianopsia, or homonymous

hemianopia, is hemianopic visual field loss on the same side of both

eyes.

Homonymous hemianopsia occurs because the right half of the brain

has visual pathways for the left hemifield of both eyes, and the left half

of the brain has visual pathways for the right hemifield of both eyes.

When one of these pathways is damaged, the corresponding visual field

is lost.

Anatomy of the Eyeball

• Fibrous Tunic:CorneaSclera

• Vascular TunicChoroid coat Ciliary Body (Ciliary muscle, Ciliary process)Iris

• Nervous TunicRetina

• 5. *The iris gives our eyes color and it functions like the aperture on a camera, enlarging in dim light and contracting in bright light. The aperture itself is known as the pupil. 

6. *The pupil is the opening, or aperture, of the iris. 

• 7. *The anterior chamber is the area bounded in front by the cornea and in back by the lens, and filled with aqueous. 

• 8. *The lens helps to focus light on the retina. 

• 9. *The vitreous humor is a transparent, colorless mass of soft, gelatinous material filling the eyeball behind the lens. 

• 6. *The pupil is the opening, or aperture, of the iris. 

• 7. *The anterior chamber is the area bounded in front by the cornea and in back by the lens, and filled with aqueous. 

• 8. *The lens helps to focus light on the retina. • 9. *The vitreous humor is a transparent,

colorless mass of soft, gelatinous material filling the eyeball behind the lens. 

• 10. *The retina is the innermost coat of the back of the eye, formed of light-sensitive nerve endings that carry the visual impulse to the optic nerve. The retina may be compared to the film of a camera. 

• 11. *The choroid, which carries blood vessels, is the inner coat between the sclera and the retina. 

• 12. *The optic nerve conducts visual impulses to the brain from the retina.  

• 13. *The artery is the vessel supplying blood to the eye. 

• 14. *The canal of Schlemm is the passageway for the aqueous fluid to leave the eye. 

• 15. *The ciliary body is an unseen part of the iris, and these together with the ora serrata form the uveal tract. 

• 16. *The macula is a small area in the retina that provides our most central, acute vision. 

• 17. *The ora serrata and the ciliary body form the uveal tract, an unseen part of the iris. 

• 18. *The posterior chamber is the area behind the iris, but in front of the lens, that is filled with aqueous. 

• 19. *The rectus medialis is one of the six muscles of the eye. 

• 20. *The vein is the vessel that carries blood away from the eye.