Eye

Question 1

The eye contains light sensitive ___

Answer 1

Photoreceptors

Question 2

Rods

Answer 2

Active when light - poor intensity

Gives rise to black and white vision

Question 3

Cones

Answer 3

Sensitive when light is high intensity

Permit color vision

Question 4

How is the eye protected

Answer 4

• eyeball is situated in a bony socket : protects everywhere except front (protected by lashes and lids). Sockets padded with fatty deposits
• eyelids lined with conjunctiva ( thin sensitive membrane). When stimulated, causes blinking and secretion of tears
• glands of Meiboom: inside eyelids, secret fluid that lubricates movem. Of eye, traps foreign particles.
• lachrymose glands release lachrymose fluid (tears): wash dust from eye, destroy germs, prevents desiccation, lubricates movem.

Question 5

What is the conjunctiva

Answer 5

Thin sensitive membrane lining eyelid

Causes blinking and tears when stimulated

Question 6

What does the lachrymal gland release and what does it do

Answer 6

Lachrymal  fluid (tears)
Washes dust from eye, destroys germs (contains lysozyme) prevents desiccation, lubricates movem.

Question 7

Which two fluids protect the eye and lubricate movem.

Answer 7

Glands of Meiboom secret fluid

Lachrymal glands

Question 8

(Functioning of the eye)

What is binocular vision

Answer 8

Ability to focus on one object using both eyes. Each eye has a separate image and the brain puts the two images together, allows us to have 3D view

Question 9

(Functioning of eye)

Describe pupillary mechanism

Answer 9

High intensity light can damage the eye, therefore it’s important the amount of light that enters is regulated. This is controlled by the iris which has circular and radial muscles which are antagonistic

Question 10

(Functioning of the eye)

Accommodation (definition)

Answer 10

The adjustment of the curvature of the lens for vision at different distances

Question 11

Describe accommodation

Answer 11

At rest: eyes adapted for viewin objects within a range of 6m
Anything closer/farther than this requires adjustment of the curvature of the lens.
The lens is stretchy and elastic, can bulge/flatten when focusing on objects at different distances.
Change of curvature changes refraction of light so the Rays fall on the retina.
Ciliary muscles and suspenders ligaments (hold the lens in position) are responsible for the curvature of lens

Question 12

(Accommodation)

What are the ciliary muscles and suspends pry ligaments responsible for

Answer 12

• holding the lens in position

- changing the curvature of the lens

Question 13

(Accommodation)

Why and how does the lens change when focusing on different distances

Answer 13

The lens is stretchy and elastic and can bulge/flatten

Question 14

Compare:
Near vision.            Vs distant vision for;
- ciliary muscles
- suspensory ligaments
- lens

Answer 14

Near vision

• muscle contracted
• slack and distance small
• bulges, thick

Distant vision

• relaxed
• tight, distant, tense
• flat, thin

Question 15

Name the four eye disorders

Answer 15

1) myopia (short-sightedness)
2) longsighted/ hyperopia/ presbyopia
3) astigmatism
4) cataracts

Question 16

Ability to focus on near objects, distant objects are blurred. Eyeball is too long, image falls in front of retina instead of on.

Answer 16

Myopia

Question 17

Can see distant objects, near is blurred. Eyeball too short, image falls behind retina instead of on.

Answer 17

Long sightedness

Question 18

Caused by an irregularly shaped cornea/ lens, causing blurred vision.

Answer 18

Astigmatism

Question 19

Cloudy region that appears on the lens due to accumulation of certain proteins in these regions. Lens no longer completely transparent, therefore harder to see.

Answer 19

Cataracts

Question 20

Can be treated with glasses/ contact lenses with concave lenses to diverge incoming light rays

Answer 20

Myopia

Question 21

Can be treated with glasses/ contact lenses specifically shaped for the particular individual.

Answer 21

Astigmatism

Question 22

Can be treated with glasses/ contact lenses with convex lenses to bend the light rays further together

Answer 22

Long sightedness/ hyperopia

Question 23

Can be treated with surgery. Clouded lens removed and replaced with a plastic intraocular lens

Answer 23

Cataracts