vision ii

Question 1

4 parts of retinal image formation

Answer 1

1. refraction
2. accomodation
3. constriction
4. convergence

Question 2

refraction

Answer 2

• bending of light rays

- cornea and lens reflect light rays

Question 3

light pathway and light rays

Answer 3

cornea –> aqueous humor –> lens –> vitreous humor –> neural layer of retina to photoreceptors

light rays bend ant/post surface of cornea and ant/post surface of lens

• most refraction at cornea
• can only modify the lens

light rays focus on retina (focal point)

Question 4

accommodation and near point of visionn

Answer 4

• increase in the curvature of the lens for near vision = accomodation
• near point of vision is min distance from eye that object can be clearly focused

Question 5

accommodation of the lens

Answer 5

• changes refraction for close vision
• normal eye: objects need to be 20 ft away to be focused on retina

-vary lens curvature to focus on objects closer and further than 20 ft (ciliary muscles and zonules)

Question 6

describe how eye adapts for close vision

Answer 6

• ciliary muscles contract (parasymp)
• decreases tension of suspensory ligaments
• lens shortens, thickens, bulges
• greater refraction

Question 7

presbyopia

Answer 7

lens loses elasticity –> need reading glasses

Question 8

describe how eye adapts for far vision

Answer 8

• ciliary muscles relax (sympathetic)
• increase tension in suspensory ligaments
• lens gets flatter
• less refraction

Question 9

refraction abnormalities and corrections

Answer 9

Nearsightedness (myopia) = close things are clear and image is focused in front of retina
-fix with concave lens

Farsightedness (hyperopia) = distant objects are clear and image is focused behind the retina
-fix with convex lens

Question 10

constriction of pupil

Answer 10

-contraction of iris muscles changes diameter of pupil

bright light/near vision

• circular muscle fibers contract (parasymp)
• constriction: decreased pupil ize

dim light/far vision

• radial muscle fibers contract (symp)
• dilation: increased pupil size

Question 11

convergence of eyes

Answer 11

• binocular vision = 2 eyes; 1 image
• medial movement of 2 eyeballs (via extrinsic muscles) so that object is focused on same spot on both retinas
• closer objects= greater convergens for single vision (eyes get more crosseyed for closer images)
• diplopia = double vision