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Ocular Physiology > Retina > Flashcards

Retina Flashcards

1
Q

layer of the retina where rod and cone membranes fuse together, creating an impediment to ion flow

A

external limiting membrane

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2
Q

layer of the retina of cell bodies of the photoreceptors

A

outer nuclear layer

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3
Q

layer of the retina where synapses are between photoreceptors and bipolar cells

A

outer plexiform layer

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4
Q

layer of the retina where cell bodies of BP cells, horizontal cells, glial cells, amacrine cells are

A

inner nuclear layer

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5
Q

layer of the retina with synapses between BP cells and ganglion cells

A

inner plexiform layer

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6
Q

layer of the retina with the footplates of Mueller cells

A

internal limiting membrane

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7
Q

rod free zone at 100 days before birth is:

A

large (1600 um in diameter)

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8
Q

rod free zone at birth is:

A

still not adult like, 400-600 um in diameter

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9
Q

rod free zone doesn’t reach adult like levels until:

A

200 days after birth (when it is 200 um)

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10
Q

what is the cone like at 22 weeks gestation

A

looks like epithelial cells, no outer segments no photopigment, cannot transduce light

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11
Q

how many days post birth is the cone the full length and pretty much adult like

A

45 days post birth

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12
Q

describe changes in retina as it reaches ora errata

A

all retinal layers form down to a single layer to the non pigmented ciliary epithelium
-lose photoreceptors first, then INL/ ONL merge, then ganglion cells lost

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13
Q

diameter of optic disc

A

1500 microns

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14
Q

what layers does the central retinal artery (CRA) supply?

A
  • nerve fiber layer
  • ganglion cell layer
  • inner plexiform layer
  • inner nuclear layer
  • little of outer plexiform layer (by diffusion?)
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15
Q

what are the cilia-retinal arteries?

A
  • coming from choroid and running to macula

- crossover vessel seen in 1/3 of population, usually see 1 but can see 2

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16
Q

choroidal circulation includes what ciliaries

A
  • long posterior
  • anterior
  • short posterior
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17
Q

2 main ways choroidal circulation is different than retinal circulation

A
  • a lot more choroidal vessels than central vessels

- choroidal vessels are larger- larger lumen diameter

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18
Q

what layers does choroidal circulation supply?

A

photoreceptors and RPE

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19
Q

size of retinal circulation capillaries vs. choroidal capillaries

A

retinal: smaller, < 10 nm
choroidal: larger, > 20 nm

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20
Q

differences in circulation leakiness of choroidal versus retinal

A

choroidal circulation more leaky and the large molecules that pass out of circulation can not enter retina because of the RPE (tight junctions at base of RPE)

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21
Q

mathematical formula for heart pressure

A

heart pressure= 80 + 1/3 (pulse pressure or 60) which =100

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22
Q

what is clinical ophthalmodynamometry used to measure?

A

arterial diastolic pressure

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23
Q

the small retinal vessels have what type of resistance and flow rate?

A
  • small vessels
  • high resistance
  • low flow rate (1.7 ml/min/gm)
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24
Q

the large choroidal vessels have what type of resistance and flow rate?

A
  • large vessels
  • lower resistance
  • high flow rate (19 ml/min/gm)
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25
Q

choroidal vasculature is under the control of the:

A

sympathetic nervous system (superior cervical ganglion)

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26
Q

relationship between IOP and blood flow in choroid

A

linear relationship

increased IOP = decreased blood flow

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27
Q

relationship between IOP and blood flow in retina

A
  • no change between 20-70 mmHg because pericytes

- linear decrease in blood flow after 70

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28
Q

oxygen consumption rate of the retina

A

67 ul/gm/hr

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29
Q

glucose consumption rate of the retina

A

106 ug/mg/hr

30
Q

70% of the oxygen consumed in the retina is used for:

A

glucose oxidation

31
Q

80% of the glucose used in the retina goes through:

A

glycolysis

other 20% goes to pentose shunt

32
Q

photoreceptors use ___ the energy produced in the retina

A

half

33
Q

neurotransmitter for photoreceptors

A

glutamate

34
Q

neurotransmitter for bipolar cells

A

glutamate

35
Q

neurotransmitter for horizontal cells

A

GABA

36
Q

neurotransmitters for amacrine cells

A

Ach, dopamine, noradrenalin, serotonin, GABA, glycine, aspartate, taurine

37
Q

neurotransmitters for ganglion cells

A

glycine, aspartate, taurine

38
Q

ERG:

A-wave is from the

A

photoreceptors

(-) wave

39
Q

ERG:

B-wave is from the

A

bipolar cells and Mueller cells

(+) wave

40
Q

ERG:

C-wave is from the

A

RPE

41
Q

ERG:

D-wave is from the

A

off response (light going off retina)

42
Q

ERG:

oscillatory potentials are from the

A

amacrine cells

b/w A and B wave in the ascending limb of B wave

43
Q

flash ERG used for

A

mueller cells

-retinal dystrophies such as retinitis pigments, Stargardts, Bests

44
Q

pattern ERG used for

A

ganglion cells

-glaucoma, diabetes

45
Q

multifocal ERG used for

A

cones, cone BP cells

-macular dystrophy

46
Q

type of occlusion with sudden loss of vision, ischemic retina with macula as cherry red spot

A

retinal artery occlusion

47
Q

what is the order of ERG drop out in retinal artery occlusion

A
  • oscillatory potentials first (amacrine cells most sensitive to lack of oxygen)
  • b wave
  • a wave does not disappear (b/c photoreceptors get nourished from choroid)
48
Q

type of occlusion with extensive retinal hemorrhages, dilated veins, possible cotton wool spots

A

retinal vein occlusion

49
Q

in an ischemic retinal vein occlusion, what ERG change can you see?

A

decrease in B wave amplitude

50
Q

as the glucose level is decreased in the retina, when do you see B-wave and A-wave disappear?

A

B-wave after 15 minutes without glucose
A-wave gone after 30 minutes
(because Mueller cells more sensitive to lack of glucose than photoreceptors)

51
Q

how many amino acids in sequence of opsin

A

348

52
Q

where does vitamin A bind to opsin

A

296th amino acid in sequence (lysine)

53
Q

opsin: where are amino terminal and carboxyl terminal

A

amino: inside disc
carboxyl: outside disc (in cytoplasm)

54
Q

1 rhodopsin can generate ____ T-GTPs

A

500

55
Q

1 rhodopsin can break down ___ cGMPs

A

1 million

56
Q

the disc is 50% protein, and 85% of that protein is:

A

rhodopsin

57
Q

the disc is 50% lipid, and that lipid is:

A

phospholipid, so that membrane is fluid

58
Q

difference in rod shedding versus cone shedding

A
  • rods shed when light comes on

- cones shed with light goes off

59
Q

how many days is life cycle of disc production?

A

9-13

60
Q

3 functions of RPE

A
  1. discs that are shed from photoreceptors are phagocytized by RPE
  2. RPE contains melanin- decreases light scatter
  3. vitamin A storage, all-trans retinol-regeneration of rhodopsin
61
Q

most common inherited disease affecting RPE

A

retinitis pigmentosa

62
Q

where retinitis pigmentosa usually begins:

A

mid-periphery (20 degrees from fovea where highest concentration of rods are)

63
Q

possible chromosomes affected by genetic mutation in retinitis pigmentosa

A

1-11, 14-17, 19, X

64
Q

retinitis pigmentosa

% X linked recessive and types

A

10%
2 types
short arm of X chromosome

65
Q

retinitis pigmentosa

% autosomal dominant and types

A

20%

over 70-100 types

66
Q

retinitis pigmentosa

% autosomal recessive

A

15%

67
Q

retinitis pigmentosa

% undetermined

A

50%

68
Q

common proteins affected in retinitis pigmentosa

A
  • proline (CCC) -> histadine (CAC) point mutation

- RDS or cGMP

69
Q

common signs of retinitis pigmentosa

A
  • blood vessels thinner and less blood to retina
  • optic disc pale
  • cells in vitreous floating around
  • posterior subcapsular cataract (PSC)- 50% of people
70
Q

what is the most clinically significant test for retinitis pigmentosa

A

ERG (16-18% decrease per year)

after ERG flatlines, then do VFs

71
Q

in electroculargrams done for retinitis pigmentosa, what ARDN ratio is considered abnormal?

A

< 1.7

72
Q

inheritance pattern and cause of Bests disease

A

autosomal dominant

-macula not normal from increased lipofuscin

Ocular Physiology (8 decks)

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