Sensory adaptation in amblyopia

Question 1

What is the VA for OKN at 1 month? 1 year? 3 years?

Answer 1

1 month: 20/100-20/400
1 year: 20/40
3 years: 20/20

Question 2

What is the VA for VEP at 1 month? 6 months?

Answer 2

1 month: 20/540

6 months: 20/20

Question 3

What is VA for FPL at 1 month? 6 months -1 year? 4 years?

Answer 3

1 month: 20/800
6months - 1 year: 20/100-20/200
4 years: 20/20 to 20/25

Question 4

_____ phenomenon is used to dx amblyopia and EF

Answer 4

crowding;

Question 5

In the amblyopic fovea, _____ interaction typically extends over an increased distance, to a degree that is roughly proportional to the reduction in acuity. Amblyopia cannot be considered cured until interactive acuity has become normal bc in real life they have to overcome contour interaction.

Answer 5

contour

Question 6

Describe the Pelli-Levi Dual Acuity chart

Answer 6

1. Observers read down the left (no noise) side of the chart until all three letters in a line are missed.
2. The difference in log acuities with/w/o noise is the observers dual acuity.

Question 7

What is PAM

Answer 7

Potential acuity meter. Mounted on a slit lamp, it projects a point source of light approximately 0.1 mm in diameter into the patient’s pupil. an image of a senile type VA chart is projected through the light source. Accurately measures VA within 1 line of true VA.

Question 8

what does an interferometer do

Answer 8

projects a high contrast sinusoidal grating pattern on the retina using the interference fringe phenomenon.

Question 9

T/F in amblyopia, acuity can be markedly overestimated using the VEP.

Answer 9

True

Question 10

In eccentric fixation, a failure of an eye in monocular vision fails to take up fixation with the fovea, but with some other point. It is only shown when the better eye is covered. It is a ______ phenomenon opposed to ARC which is a BINOCULAR phenomenon.

Answer 10

monocular

Question 11

How do you assess fixation

Answer 11

1. centricity (central vs eccentric)
2. magnitude
3. quality of fixation (steady vs unsteady)
4. pattern of fixation (drifts, saccades, nystagmus)
5. percent foveation
6. directional bias

Question 12

what are the four theories as to the cause of EF

Answer 12

1. Suppression theory
2. ARC- resulting from a central scotoma in the amblyopic eye (EF secondary to this)
3. Motor Theory- failure of the EOM to relax from the deviation. habitual strabismic deviation causes an adaptive after-effect which modifies the subsequent monocular localization.
4. Pickwell: a sequal to an enlargement of panum’s fusional area following decompensated heterophoria at an early age- leads to microtropia (loss of accurate correspondence)

Question 13

Eccentric viewing refers to the eccentric point be localized eccentrically and the fovea centrally. Pt’s describe objects being slightly to one side. the key is _____ of the eccentricity

Answer 13

awareness

Question 14

Past pointing test is related to ______. carry out test initially with good eye.

Answer 14

localization; if they don’t touch tip with finger and other eye occluded means fixation does not coincide with the center of localization.

Question 15

When doing the corneal reflex test, the relative displacement of the reflex by 1 mm = _____degrees of ____PD

Answer 15

11; 20

Question 16

with the ______ chart, amblyopes often have small foveal scotoma that shows up on this chart and occurs centrally if central localization, eccentrically if EF.

Answer 16

amsler

Question 17

what does the after image transfer test measure?

Answer 17

Eccentric fixation and ARC;
only used after you have diagnosed the abnormal fixation to measure its magnitude. After images are transferred to normally corresponding points in the other eye. You have to occlude the AE, and have pt fixate on center of the strip. occluder is then changed to the good eye, and pt looks at a small fixation target, the after image then appears a few seconds later, and asked to locate position of after image in relation to the fixation point.

Question 18

What is the best method to detect Eccentric fixation?

Answer 18

Haidinger’s brushes

Question 19

What is the formula for VA and eccentric fixation

Answer 19

20/x = 1/MAR

Question 20

Pt with 5 deg of EF. How do you calculate expected VA?

Answer 20

1. 5 x 1.75
= 8.75 PD
2. 8.75 + 1 = 9.75 MAR
3. 20 x 9.75 = 195
4. VA = 20/195

Question 21

T/F while doing NDF test, pt wears current rx, the normal eye is occluded first, and then repeated in other eye. If there is a little difference with and without the filter, the defect is most likely caused by amblyopia.

Answer 21

True