Hereditary Disease and Horizontal Cells (M1)

Question 1

What is the type of ERG that gives a measure of overall retinal activity? 1. What is the problem with this? 2

Answer 1

1. full-field ERG

2. no good at picking up focal defects

Question 2

What type of ERG uses an algorithm to sort out the ERG for the corresponding retinal areas that were stimulated by each hexagon?

Answer 2

muti-focal ERG

Question 3

What are electrodiagnostic tests (like EOG and ERG) used for?

Answer 3

diagnosis of hereditary retinal and choroidal diseases and monitor progression

Question 4

What test is useful for the diagnosis of vitelliform dystrophy (Best’s disease)? 1. What separates this test from the other possible one? 2. What is the inheritance of the disease? 3

Answer 4

1. EOG
2. EOG is abnormal for adult carriers and ERG is normal for them
3. autosomal dominant

Question 5

During Best’s disease, what deposits in the RPE? 1. When are pigment disturbances usually observed? 2

Answer 5

1. lipofuscin

2. 5-10

Question 6

What is the progression in the appearance of a lesion during Best’s disease?

Answer 6

Look like egg yolk then rupture and hemorrhage and look like scrambled egg

Question 7

What is the lesion rupture during Best’s disease associated with?

Answer 7

1. focal RPE degeneration

2. choroid atrophy

Question 8

What are the different inheritance types (with the percentage of each) for retinitis pigmentosa?

Answer 8

1. autosomal dominant (30-40%)
2. autosomal recessive (50-60%)
3. X-linked (5-10%)

Question 9

What percentage of people with RP have no known prior family history?

Answer 9

50%

Question 10

What are the common symptoms of RP that affects the rods more (rod-cone RP) than the cones?

Answer 10

1. nyctalopia

2. loss of peripheral vision

Question 11

What are the common symptoms of RP that affects the cones more (cone-rod RP) than the rods?

Answer 11

1. acuity loss
2. photophobia
3. photopsia
4. color vision concerns

Question 12

What are the classic fundus findings in RP patients?

Answer 12

1. pigment clumping in the peripheral retina (bone spicule)

2. attenuated (narrow) retinal arteries

Question 13

What tool can help to diagnose RP, by detecting the changes that precede fundus changes, and monitor the progression?

Answer 13

ERG

Question 14

What type of ERG is typically affected in rod-cone RP? 1. Cone-rod RP? 2

Answer 14

1. scotopic ERG

2. flicker ERG and mixed ERG

Question 15

What gene do the most common defects for autosomal dominant RP occur?

Answer 15

rhodopsin gene

Question 16

What process do gene defects often affect in RP? 1. What are the genes involved? 2

Answer 16

1. photodransduction

2. PDE6, RPE65, CNGA/B

Question 17

If the visual disturbances associated with RP are present at birth what do they normal characterize it as? 1. What is the gene affected? 2. What is being looked at as a possible treatment for this? 3

Answer 17

1. Leber’s Congenital Amaurosis
2. RPE65
3. gene therapy

Question 18

What are the retinal disorders in which neurotransmission is altered between photoreceptors and bipolar/horizontal cells called?

Answer 18

Congenital stationary night blindness

Question 19

What is the presentation of type 1 congenital stationary night blindness? 1. What cells does the defect affect? 2

Answer 19

1. complete absence of rod pathway

2. localized to ON bipolar signaling

Question 20

Where is the genetic defect in x-linked type 1 congenital stationary night blindness?

Answer 20

nyctalopin (in dendrites of ON bipolars)

Question 21

Where is the genetic defect in autosomal recessive type 1 congenital stationary night blindness?

Answer 21

TRPM1 in mGluR6

Question 22

What is the presentation of type 2 congenital stationary night blindness? 1. What is the inheritance? 2. Where is the genetic defect? 3

Answer 22

1. incomplete form
2. x-linked
3. specific VGCC found in PRs (ON -related)

Question 23

What are the symptoms of CSNB?

Answer 23

1. nyctalopia
2. normal visual acuity (type 2 usually)
3. severe reduction is VA (type 1 usually)

Question 24

What is the appearance of the fundus in CSNB? 1. What is used to help diagnose this? 2

Answer 24

1. usually normal

2. ERG

Question 25

What changes in the ERG reading of a patient with CSNB?

Answer 25

normal A-wave but no B-wave

Question 26

What is the current treatment of retinitis pigmentosa?

Answer 26

1. counseling and low vision regimes

2. vitamin A supplementation

Question 27

What cells are horizontal cells in strategic position to influence? 1. Where are they located? 2

Answer 27

1. bipolar cell responses

2. outer margin of the inner nuclear layer

Question 28

What makes horizontal cells unique in their neuronal synapes’?

Answer 28

post-synaptic to PRs and act as pre-synaptic terminals

Question 29

Do horizontal cells depolarize or hyperpolarize to light? 1. Are they an action potential or graded? 2

Answer 29

1. hyperpolarize

2. graded

Question 30

What kind of receptors are found on the dendritic/axon terminals of horizontal cells that respond to glutamate? 1. Are they sign-conserving or inverting? 2

Answer 30

1. ionotropic kainate/AMPA-type receptors

2. sign-conserving

Question 31

What is the area over which stimulation leads to a response in a particular sensory neuron?

Answer 31

receptive fields

Question 32

What is the photoreceptor receptive field limited by?

Answer 32

width of outer segment

Question 33

What do horizontal cells have that allow their receptive field to not just be limited by the extent of their dendrites alone?

Answer 33

gap junctions allowing ions and small molecules to pass directly from one cell to another