Eye Care: Parts and Functions of the Eyes

1. Retinal blood vessel,
2. Choroid: Blood vessels within this layer supply the eye with essential nutrients,
3. Retina: This innermost layer of the eyeball contains nerve fibers and light-sensitive cells,
4. Optic disk : This area, where the optic nerve leaves the eye, lacks light-sensitive cells and is also known as the ‘blind spot’,
5. Optic nerve: Nerve impulses travel along the optic nerve from the retina to the brain,
6. Eye muscle: Six muscles surround the eye, allowing it to rotate in any direction,
7. Fovea: The fovea, at the centre of the macula, is packed with light- sensitive cells and is the most sensitive part of the retina,
8. Vitreous humour: The back part of the eye is filled with a jelly-like substance called vitreous humour,
9. Lens : The elastic lens can change shape to focus light rays from both near and distant object, 10. Sclera : The tough sclera is the white of the eye, forming the outer coat of the eyeball,
11. Conjuctiva: This thin, transparent membrane covers the white of the eye andforms the lining of the eyelids,
12. Aqueous humour: This watery fluid, produced by the ciliary body, fills front chamber of the eye, which is between the lens and the cornea,
13. Cornea: This transparent cornea at the front of the eye plays an important role in focusing light rays,
14. Pupil: Light enters the back part of the eye through the pupil, the opening in the centre of the coloured iris,
15. Iris: The coloured iris of the eye contains muscles that control the size of the pupil,
16. Suspensory ligament: The fibers of the suspensory ligament attach the lens to the ciliary body,
17. Ciliary body: The ciliary body controls lens thickness to focus light correctly; it also secretes aqueous humour,
18. Skull bone: The bony orbit of the skull protects the eyeball.

1. The Ciliary ring which adjoins the choroid.

2. The Ciliary Processes : It is a series of about seventy radial ridges behind the iris to which suspensory ligament of the lens is attached.

3. Ciliary Muscles : Contraction of these ciliary muscles accounts for altered curvature of the lens (as explained above under the caption ‘accommodation’ which may be seen.)

Eye-Ball: It is body of the eye and is roughly spherical. It lies in the orbit and is bounded by sclera. It has close relation with associated accessory structures viz., conjunctiva, lachrymal apparatus and eyelids and the three extrinsic eye-muscles control its movement.

Eye-Brow : It is a small fringe of hair, just above the eye, where bony ridge is located. For ladies, it is a sign of beauty but its purpose is to prevent moisture, water, sweat-drops running into the eye. Both the eye-brows resemble a bow. Not only that but raised eye brows indicated anger or surprise and lowered eyebrows are raised upper eye, lids close the eyes, partially or fully). Eye-brows are parameters of our (sudden) change in mood and expression.

Eye-Lash : It is the long stiff hairs which form a row that projects outward from the frontal edge of the lower and upper eye lids. They help to keep away the dust and other finer particles from entering into the eyes. Just imagine how ugly and clumsy a person would look if he had no eye-lashes. Eye-lashes also form and enhance beauty of the eyes and ladies, in particular, keep them well-groomed and good-looking.

Eye-Lid : Each eye has two lids each—one lower and one upper. Each pair of eye-lids provides a covering to the eye. Each eye-lid consists of skin, muscle and connective tissue. Each one of the eye-lids is lined (inside) with a membrane called conjunctiva and is fringed with eyelashes. Stimulation of the pain receptors in the cornea causes the eye-lids to close in reflex action. Eyelids are protective guards of eyes because they automatically close even when there is a remote chance of foreign body entry into the eye. They also protect our eyes from entry of water, wind, heat, dust, and other harmful foreign matters.

Eye-Ground : It is an ocular fundus of the eye, which can be viewed through an instrument called ‘ophthalmoscope.’

Part I

Sclero—situated in the posterior (back) part.
Cornea—situated in the frontal part (anterior).

Part II

Choroid—situated at the back.
Iris—situated in the front part.

Part III

Retina and there are two chambers—posterior and anterior.

Refractive media: These can be subdivided into three division, viz.

□ Vitreous Humour—situated in the posterior chamber
□ Aqueous Humour—situated in the frontal part.
□ Crystalline—LENS—situated on posterior wall.

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