special systems

Question 1

what values does the visible light spectrum lie between?

Answer 1

400-750nM

Question 2

what is the optical disk?

Answer 2

the head of the optic nerve where axons exit the eye. no light sensitivity at this part= the blind spot of the eye

Question 3

what two structures are involved in refraction of light in the eye. which one does the most and which is for fine tuning?

Answer 3

cornea- responsible for the greatest amount of refraction
lens- fine tuning of refraction

Question 4

at rest what is the refractive power of the eye?

Answer 4

60 diopters, focal point of approx 1.7cm behind the lens

Question 5

what adjustments does the eye have to make to view distant objects?

Answer 5

cillary muscle relaxed, pipil dilates, lens flattens, zonial fibres are under tension and refractive power is decreased.

Question 6

what adjustments does the eye need to make to view close objects?

Answer 6

cillary muscle contracted, relaxed zonial fibres, lens curves increasing refractive power and pupil size constricts

Question 7

what are the three aspects to the near response?

Answer 7

1) accomodation, changing the shape of the lens
2) constriction of the pupil (sphincter pupillae muscles contracting)
3) convergence of the eyes

Question 8

what is emmetropia?

Answer 8

normal vision
refracted light (parallel and diverging) all focus on the retina

Question 9

what is hyperopia?

Answer 9

farsightedness- eyeball too short rays dont focus on retina

Question 10

what is myopia?

Answer 10

nearsightedness
eyeball too long - things at distance not focussed
rays focus infront of the retina
correction is through a concave lens