lecture 5 electrical potentials 1

Question 1

what are the 3 types of electrical recording of the eye used to diagnose ocular disease?

Answer 1

EOG, ERG, VEP

Question 2

The front of the eye has a slight ___ charge, and the back of the eye has a slight ____ charge

Answer 2

positive, negative

Question 3

an EOG measures the ____ difference on the eye

Answer 3

dipole

Question 4

An EOG is efficient in diagnosing ____ disease

Answer 4

Best’s

Question 5

what are the normal and abnormal arden ratio numbers

Answer 5

normal=2.5, abnormal=less than 1.9, (bests disease is typically 1.2 or 1.3)

Question 6

an EOG can also be used for….

Answer 6

sleep studies, (very efficient at determining REM state), eye tracking technology for military or paralyzed patients.

Question 7

in an EOG, where do you connect the electrodes?

Answer 7

temporally and nasally

Question 8

what is an arden ratio?

Answer 8

light/dark ratio as determined by an EOG

Question 9

what disease develops a patellaform (splattered egg-looking) macular degeneration often resulting in choroidal neovascularization into the retina, resulting in blindness?

Answer 9

Bests disease

Question 10

ERG measures….

Answer 10

retinal current…flashing lights induce electrical change in the retina

Question 11

an ERG basic waveform has what 5 parts?

Answer 11

a=rods and cones, b=on bipolarcells and muller cells, c=RPE, d=off bipolar cells, op’s=amacrine cells

Question 12

What is an OP?

Answer 12

oscillitory potential, found on the upswing between a and b waves

Question 13

where do the ticks of the oscillatory potential come from

Answer 13

amacrine cells

Question 14

a device that has a forehead rest, a chin rest, and 3 gaze position holes inside a dome is called a….

Answer 14

ganzfeld stimulator, used as the stimulus source during an ERG reading.

Question 15

which wave of the ERG waveform happens when the lights go out

Answer 15

d-wave

Question 16

what 3 things are placed on the patient for an ERG reading?

Answer 16

a lens/wire placed on cornea, a ground on the ear, a reference point on the forehead

Question 17

what are the 2 basic ERG measurements?

Answer 17

wave propagation time (implicit time) and amplitude.

Question 18

a 30 Hz flicker flashes ___ times per ____

Answer 18

30, second

Question 19

what inhibits oscillatory potentials?

Answer 19

glycine

Question 20

what method can you use to isolate oscillatory potentials?

Answer 20

30hz flicker

Question 21

what part of the ERG waveform represents ganglion cells?

Answer 21

none, you never see ganglion cell activity in the ERG waveform

Question 22

name 4 classic abnormal ERG findings

Answer 22

complete CSNB (congenital stationary night blindness), rod monochromatism, cone dystrophy, retinitis pigmentosa

Question 23

describe the ERG waveform of a patient with a retinal detachment…

Answer 23

nearly a flat line

Question 24

true or false: ERG wave amplitudes are inversely proportional to light intensity?

Answer 24

true, when pt is dark adapted the amplitudes are larger.

Question 25

When doing an ERG, you will want to measure photopic and scotopic, but in which order and why?

Answer 25

measure scotopic first then photopic, it takes less time if the patient is dark adapted first.

Question 26

stargardt’s disease targets:

a) ganglion cells
b) rods
c) amacrine cells
d) cones

Answer 26

d) cones

Question 27

An ERG reading with a flat line for the photopic 30hz flicker would be:

a) complete CSNB
b) rod monochromatism
c) cone dystrophy
d) retinitis pigmentosa

Answer 27

rod monochromatism, since there is no cone function with this disorder

Question 28

An ERG reading with a flat line for the rod specific would occur in which two:

a) complete CSNB
b) rod monochromatism
c) cone dystrophy
d) retinitis pigmentosa

Answer 28

a) complete CSNB, night blindness=no rod function
d) retinitis pigmentosa=no rod function due to peripheral vision loss which travels inward leaving the very center of the macula, causing tunnel vision, and leaving only photopic vision

Question 29

an ERG reading with an electronegative spike for the maximum scotopic response would occur in which:

a) complete CSNB
b) rod monochromatism
c) cone dystrophy
d) retinitis pigmentosa

Answer 29

a) complete CSNB

Question 30

An ERG reading with a “undetectable/blink artifact” v-shaped wave for transient photopic would occur in:

a) complete CSNB
b) rod monochromatism
c) cone dystrophy
d) retinitis pigmentosa

Answer 30

b) rod monochromatism

Question 31

ERG findings for cone dystrophy show….

Answer 31

normal on rod specific, moderate reduction on max scotopic responses, small and slow (decreased cone function) for photopic flicker and transient photopic.

Question 32

true or false: red light enhances your mesopic vision

Answer 32

true, it combines light sensitivity with clarity and rods and cones work closely together in your favor. thats why a dark room (used for photo developing) has a red light.

Question 33

a blue light is soley ___ response

Answer 33

rod

Question 34

true or false: an ERG is spectrally sensitive

Answer 34

true, we can use different wavelengths of light to get the ERG to respond differently. (red gives a mesopic response, while blue gives a rod only response)

Question 35

what is the difference between a focal ERG and a multifocal ERG?

Answer 35

Focal involves stimulating a small point on the retina, multifocal involves over 200 points on the retina. With multifocal, stimulus comes from an LCD screen rather than a ganzfeld.

Question 36

An mfERG 3-D image with a central hole an warm colors surrounding the center describes…

Answer 36

Stargartds disease-scotoma in macula, loss of central retina function, looks similar to AMD, however, this will show up in younger patients.

Question 37

An mfERG 3-D image with a prominent cone in center with warm colors, however, the surrounding area is blue-ish/dark describes

Answer 37

retinitis pigmentosa-no peripheral vision, cone is very pointy because only very central vision is left.

Question 38

An mfERG 3-D image with blue-ish/green flatter plane with no central cone describes…

Answer 38

Best’s disease-absence of cone represents no central vision, the darker the color the lower the retinal activity. leads to blindness.

Question 39

An mfERG 3-D image with incomplete central cone and normal warm colors surrounding cone describes….

Answer 39

AMD- incomplete cone represents macular degeneration. pt will have peripheriphal vision intact.