The External Eye

 

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The eyelids protect the eye and keep the front surface of the eye moist.

The cornea is the clear window at the front of the eye. Its curved shape helps focus light rays. Injuries or disease can cause scars or clouding of the cornea which may affect vision.

The sclera is the tough, white outer coat of the eye.

The conjunctiva is a thin transparent coat covering the sclera and the inner parts of the eyelids.

The iris is the coloured part of the eye which changes size to control the amount of light entering through the pupil.

The pupil is the opening (gap) at the centre of the iris. In bright light the pupil becomes small. In dull light the pupil is larger to allow for more light to enter.

More information on the parts of the eye can be found in The Internal Eye later in this chapter

Six rules for a normal healthy eye

1. The eyelids should open and close properly 2. The conjunctiva should be clear. 3. The cornea should be clear 4. The pupils should be black, round and the same size 5. The eye movements should be smooth and able to look in all directions 6. The vision should be good

Checkpoint:

What is the name of the white part of the eye?

What is the name of the central gap in the eye that usually appears black?

What is the name of the coloured part of the eye?