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Question 2

Emmetropia

Answer 2

match b/w focal length and length of eyeball

Question 3

Myopia

Answer 3

“near-sighted” light from objects far away are refracted to much –> focus object in front of retina concave lens to correct (diverge light a little)

Question 4

Hyperopia

Answer 4

“far-sighted” objects (particulary close) are focused behind the retina –> to little convergence convex lens to correct –> aids in convergence

Question 5

astigmatism

Answer 5

focal planes are not the same in all meridians –> blurred visionregular - toric eyeballirregular - cornea irregularity

Question 6

lens formula

Answer 6

1/f = N-1 (1/R1 - 1/R2)1/f = refractive power (diopters) convex lens = + diopter (convergent) concave lens = - diopters (divergent)

Question 7

Site of greatest refractory power?

Answer 7

anterior corneairregularity can cause astigmatism

Question 8

accomodation

Answer 8

cilliary muscles relax –> lens balls up –> decrease radius of curvature –> increase refractory poweroccurs when object close up

Question 9

The Near response

Answer 9

1. accomodation2. pupil constriction3. convergence of the eyes

Question 10

presbyopia

Answer 10

loss of accommodation w/ agenear point continually increases w/ ageConvex lens/ increased refractory power -> treatment

Question 11

Pupil constriction: effect and mechanism

Answer 11

increases depth of field but loses peripheralsANS controls: sympathetic = mydriasis (dilation) via papillary dilators; parasymp = miosis (constriction) via papillary sphincters

Question 12

Retina layers

Answer 12

PREPhotoreceptor layerouter nuclear layerouterplexiform layerinner nuclear layerinnerplexiform layerganglion cell layeroptic nerve layer

Question 13

region of highest accuity

Answer 13

fovea - center of optical axis - all cones w/ 1:1 cone to bipolar cell ratio; no blood vessels or ganglia so little light scattering

Question 14

cones

Answer 14

High acuity and low sensitivity a few photoreceptors per bipolar cellfunction in high light and have color vision quickly “bleach” in dim light3 different opsin types –> color vision

Question 15

rods

Answer 15

Low acuity and high sensitivity many photoreceptors per bipolar cellfunction in low light and only have black and white visiononly 1 opsin type

Question 16

Critical Fusion Frequency

Answer 16

frequency at which continuous flashes of light appear to be continuous rather than flickeringin normal light - CFF greatest in foveain dim light - CFF greater in peripheral retina (b/c more rods)

Question 17

Spectral Sensitivity

Answer 17

bright light - see longer wavelengths better (Photopic) see red betterdim light - see lower wavelengths better (scotopic) don’t see red wellknown as purkinje shift

Question 18

Absolute sensitivity

Answer 18

threshold to light sensitivity is much lower in dim light but takes time for threshold to fall (dark adaptation) - more sensitive due to rods high sensitivity to lightrod photopigment must regenerate and recycle upon entering dark environment rods act fast to light, but recycle very slowly

Question 19

Light Reaction

Answer 19

Light hits rhodopsin –> transducin g protein –> Phosophodiesterase –> decrease cGMP –> close Na channels –> hyerpolarization –> decrease inhibitory neurotransmitter release from photoreceptors –> increase ganglion firing to brain