Eyes

Question 1

Three layers

Answer 1

Schleroid
* White of the eye
* Continuous with cornea

Choroid
* Blood vessel layer
* Iris and ciliary body

Retina
* Back and sides only
* photoreceptors

Question 2

Vitreous and Aqueous Humour

Answer 2

Vitreous humour (behind lense)
-Gelatinous, thick
-Maintains shape of eye

Aqueous humour
-Provides nutrients to the cornea
- 5 mL/day, comes through front of lease

Question 3

Glaucoma

Answer 3

-Blocked drainage duct

-Aqueous humour fluid builds

-Build-up of pressure, eye gets elevated pressure

• Can damage nerve

-throws off sizes and causes blurry vision

Question 4

Iris and Pupil

Answer 4

Pupil
-Eye opening for light

Iris
-Colour of the eye
-Controls amount of light entering eye

• Circular muscles constrict pupil (get smaller, limit light)
• Radial muscles dilate pupil (pulls them open, done in dark)

Question 5

Convex structures of eye produce
convergence of diverging light rays that reach eye

Answer 5

defracting pattern
- bent in
-diverging

Images formed on the retina are upside down and are only a small fraction of the object’s actual size

Question 6

Refraction is a result of

Answer 6

Cornea, doesn’t bend
* Contributes most to refraction
* Refractive ability remains constant because curvature never changes

Lens
* Refractive ability can be adjusted by changing curvature as needed for near
or far vision
- allows focus of near/far

Question 7

Accommodation

Answer 7

For far vision
-Light rays are parallel – need less bending
-Lens should be flatter, doesn’t need to be as strong

For near vision
-More bending needed, focus on retina
-Rounder lens, fatter and rounder

contracted = lower tension and more rounded lens

relaxed = higher tension and more flattened lens

Involves:
-Ciliary muscles - changes lens
-Suspensory ligaments - springs of trampoline

Question 8

Near vs Far accommodation

Answer 8

For far vision
-Ciliary muscles relax
-Suspensory ligament are pulled taut (tight)
-Lens is flatter / weaker

For near vision
-Ciliary muscles contract
-Suspensory ligaments go slack
-Tension in lens causes it to become rounder/stronger

at rest=far vision

out of focus is going from far to near and light rays don’t bend in time due to changing lens shape

Question 9

Lenses

Answer 9

Convex lens
-convergent
-Bends light rays in
-Eg. Lens of eye

Concave lens
-divergent
-Bends light rays out

Question 10

Eye conditions

Answer 10

Emmetropia
-Normal vision

Myopia (can’t see far)
-Near-sightedness
-Lens is too strong or eye
too long (bending rays too much)
-Focus is in front of retina
-Corrected with a concave lens
- prescription makes lenses weaker

Hypermetropia or hyperopia
-Far-sighted-ness (only see far)
- Lens too weak or eye to short (not bending enough)
-Focus is behind retina
-Corrected with a convex lens
- prescription makes lenses stronger

-want focus on retina

Question 11

Presbyopia

Answer 11

-Loss of near vision with age
Due to stiffening of lens
-Harder to become round
-Correct with reading
glasses