Topic 12—Disorders of vision and hearing

Question 1

How does vision work

Answer 1

The eyes contain cells called photoreceptors that generate action potentials
in response to light.

These action potentials are sent to the brain via the optic
nerve.

Accessory structures include the palpebrae (eyelids). The conjuctiva is the
membrane covering the inner surface of the palpaebrae and the ‘whites’ of the
eyes.

The lacrimal glands secrete lacrimal fluid that contains antibodies, mucus
and lysozyme.

Question 2

emmetropic

Answer 2

normal vision

Question 3

Myopia

Answer 3

short sightness

is an inability to focus clearly on distant
objects

Question 4

hyperopia

Answer 4

hyperopia or ‘long sightedness’ is an inability to focus clearly on close objects

Question 5

What causes Myopia and hyperopia

Answer 5

Myopia is caused by the eyeball being too long and hyperopia is caused by it being too short.

Question 6

Explain Presbyopia

Answer 6

As we age the lens of the eye becomes progressively less flexible, making it harder to focus on
close objects.