The Eye

Chapter 3

The Eye

The eye is made up of several important structures (they are so important that you will need to know them for your test).

CorneaPupilIrisLensRetina

Cornea

Captures lightSensitive to touch, temperature and

chemicalsA touch causes an involuntary closing of

the eyelid

Possibly the creepiest picture ever taken

Pupil

Opening for light waves to enter the eye (by product of the Iris)

Appears black because the light is absorbed by tissues inside the eye

Pupil

Iris

Regulates the amount of light by controlling the size of the pupil

Because it is a muscle, it can atrophy and wear out.

The colored part of the eye

Iris

Lens

Focuses light, with the help of the iris, onto the retina.

Changes shape to help focus on objects at various distances.

Deals with nearsightedness and farsightedness.

Lens

The Retina

A thin layer of nerve fibers lining the inner area of the eye (Like the film on a camera).

If light entering the eye does not hit the retina, it will not be sensed.

Too much retinal pressure (glaucoma) can lead to blindness or a blown out retina.

The Retina

Blind spots

The hole in the back of the eye in which there are no cones or rods.

The hole is called the optic disk.

Each eye has one blind spot where the visual field is interrupted.

Blind spots

Fortunately, your 2 eyes coordinate in such a way that they make up for the blind spot by working together.

A person that loses an eye will have a blind spot to deal with.

Optic Nerve

The pathway from the eye to the brain for neural impulses.

Half of the fibers from each eye travel to each hemisphere of the brain.

Each eye is controlled by both sides of the brain. This works to synchronize your eyes.

Optic Nerve