12 EYE

What is the function of the lacrimal gland?

Produces tears that drain into the nasal cavity through the lacrimal duct. Tears moisten and lubricate the eye surface and contain enzymes that kill bacteria.

The oil component found in tears is produced by which glands?

Tarsal glands; these are sebaceous glands inside the eyelid that produce sebum/oil to lubricate the eyeball.

Why can corneas be transplanted without typical tissue rejection?

The cornea is avascular, except around the periphery, so there is no tissue rejection when transplanted.

What is another term for the zonule?

Suspensory ligament of the lens.

Describe presbyopia.

Old eyes; occurs around age 45-50. The lens cannot accommodate because it loses flexibility and stays positioned for seeing far, causing trouble focusing on near objects.

What are cataracts?

Clouding of the lens.

What is the function of the iris?

Constriction or dilation of the pupil regulates how much light reaches the visual receptors of the eye.

What region of the retina has the highest amount of cones?

Fovea centralis; the center point of the macula with the highest concentration of cones.

Visual information travels from the retina deep into the brain via which pathway, and is it visible with an ophthalmoscope?

Optic chiasma; it is on the brain surface, so it is not visible with an ophthalmoscope.

After traveling through the optic chiasma, which section of the brain receives visual information?

Occipital region of the brain.

Which 6 structures are visible when an ophthalmoscope is used to look inside the eye?

Optic disc, fovea centralis, macula, lens, retina, and blood vessels.

What causes retinal detachment, does it cause blindness immediately, and does the detached portion contain capillaries?

Usually caused by a blow to the eye. It does not cause blindness immediately; it takes a few hours. The detached portion still has some capillaries supplying oxygen for a few hours.

Why is retinal detachment considered a medical emergency?

If not lasered back into place immediately, permanent blindness can result.

Describe hyperopia.

Eyes are too short. The person is farsighted: they can see far away but cannot focus close up. It is not the same as presbyopia.

What causes myopia?

Eyes that are too long; the person is nearsighted and can see close up but not far away.

How do hyperopia and presbyopia differ?

In hyperopia the lens can accommodate, but in presbyopia it cannot.

What is astigmatism?

An irregular shape of the cornea.

What is glaucoma?

Increased pressure within the anterior chamber of the eye; it leads to blindness.

What are the 4 main conditions that cause blindness?

Macular degeneration, cataracts, glaucoma, and diabetic retinopathy.

What is the 20-20 rule?

Every 20 minutes, look up for 20 seconds at something 20 feet away.