Optics

Question 1

Distance vs. Near Vision

Answer 1

At 20 ft or greater, light travels parallel. So less convergence is needed to focus light on the retina. Inside 20 ft, the rays are divergent

Question 2

Emmetropia

Answer 2

Ideal, rays focused onto retina

Question 3

Myopia

Answer 3

Rays focus in front of retina (maybe bc of larger eyes). Nearsightedness

Question 4

Hyperopia

Answer 4

Rays focus behind retina, farsightedness

Question 5

Astigmatism

Answer 5

Rays focus in 2 different points from rugby-ball shaped cornea w/ 2 curvatures

Question 6

The Near Triad of Accomodation

Answer 6

Pupillary constriction
Convergence of eyes
Crystalline lens increases in plus power

Question 7

3 Corrective Lenses

Answer 7

Myopia: Minus lenses made apex to apex increase divergence
Hyperopia: Plus lenses made base to base to increase convergence
Astigmatism: Toric lenses which are glass w/ two radii of curvature 90 degrees apart

Question 8

Presbyopia

Answer 8

Age Related Farsightedness, decreased ability of lens to accommodate to near object from weakening of ciliary muscle and hardening of lens. Hold things further away and turn on lights to cause pupillary constriction

Question 9

Accommodative Esotropia

Answer 9

Overconvergence in accommodation, one of most common types of strabismus in childhood. Corrected w/ glasses

Question 10

Distribution of Cones and Rods

Answer 10

Cones way highest at fovea and macula, and rods increase outside of that

Question 11

3 Ranges of Luminance

Answer 11

Scotopic - darkest
Mesopic - moonlight
Photopic - good acuity

Question 12

3 Kinds of Dichromats

Answer 12

Protanopia: Red absent
Deuteranopia: Green absent
Tritanopia: Blue absent

Question 13

Phototransduction Mech

Answer 13

Photon stimulates rhodopsin (in rods). Changes conformation to all-trans retinal. Transducin GPCR is activated. Activates PDE. Hydrolyzes cGMP, reducing its concentration. This causes Na channels to close

Question 14

Photopic vs. Scotopic Phototransduction

Answer 14

Photopic - low cGMP - Na channels close - hyperpol - less Ca channel opening and less release of NTs
Scotopic opposite

Question 15

Biphasic Waveform ERG

Answer 15

a wave corresponds to PhotoR signaling in response to stimulus, b wave in response to these + Muller plus pretty much all other cells

Question 16

Retinitis Pigmentosa (symptoms, sign, treatment)

Answer 16

Retinal dystrophy resulting in nyctalopia/tunnel vision that may progress to loss of central vision as well. Mottling of RPE with black-bone spicule pigmentation. Vitamin A may delay progression

Question 17

Receptive Field

Answer 17

On center ganglion cell will respond if center of its visual field activated, off center opposite. Both respond weakly if all is activated. This allows for contrast and resolution

Question 18

Horizontal Cell Function

Answer 18

Communicate through gap junctions and converge signals onto bipolar cells

Question 19

Graded Responses vs. AP

Answer 19

PhotoRs, horizontal, and bipolar cells use graded for fast and continous transmission of info
Amacrine and Ganglion cells convert graded into APs for long distance transmission

Question 20

Big Difference b/w Moderately Dark Adapted and Extremely Adapted Eye

Answer 20

Rods communicate via electrical synapses via cone bipolars vs. cones don’t work so communicate via rod bipolars

Question 21

3 Kinds of Retinal Ganglion Cells (RGCs) (& what they do)

Answer 21

Ps respond to changes in color
Ms respond to low contrast stimuli
Ks always on to blue and off to red and green cones. First ones damaged in glaucoma so do tests w/ blue backgrounds to determine

Question 22

Nasal Step

Answer 22

Loss of vision around nasal area, classic sign of glaucoma