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Flashcards in Optics Deck (22):
1

Distance vs. Near Vision

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

2

Emmetropia

Ideal, rays focused onto retina

3

Myopia

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

4

Hyperopia

Rays focus behind retina, farsightedness

5

Astigmatism

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

6

The Near Triad of Accomodation

Pupillary constriction
Convergence of eyes
Crystalline lens increases in plus power

7

3 Corrective Lenses

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

8

Presbyopia

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

9

Accommodative Esotropia

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

10

Distribution of Cones and Rods

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

11

3 Ranges of Luminance

Scotopic - darkest
Mesopic - moonlight
Photopic - good acuity

12

3 Kinds of Dichromats

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

13

Phototransduction Mech

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

14

Photopic vs. Scotopic Phototransduction

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

15

Biphasic Waveform ERG

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

16

Retinitis Pigmentosa (symptoms, sign, treatment)

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

17

Receptive Field

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

18

Horizontal Cell Function

Communicate through gap junctions and converge signals onto bipolar cells

19

Graded Responses vs. AP

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

20

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

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

21

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

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

22

Nasal Step

Loss of vision around nasal area, classic sign of glaucoma