Abnormal Visual Development: Amblyopia

Question 1

Amblyopia is a disease of ______. It is a unilateral/bilateral condition in which the best corrected VA is poorer than 20/20 in the absence of any obvious structural anomalies or ocular disease

Answer 1

exclusion

Question 2

Amblyogenic factors is a disease of ______. Amblyopia is always associated with strabismus, anisometropia, an episode of image deprivation or a combination of the 3 early in life usually before age 6/8

Answer 2

inclusion

Question 3

The prevalence of amblyopia ranges from ____% to _____ % depending on the population studied and the definition used.

Answer 3

1.6; 3.6

Question 4

Amblyopia effects all aspects of vision including:

Answer 4

1. Reduced CS and visual resolution.
2. Inc sensitivity to contour interaction (crowding)
3. abnormal spatial distortions and uncertainty
4. unsteady/inaccurate monocular fixation
5. inaccurate accommodative response.

Question 5

Amblyopia is categorized by ____ amblyopia, ____ amblyopia, ____ deprivation amblyopia, or it could be idiopathic.

Answer 5

1. refractive: anisometropic/isometropic
2. strabismic
3. form (congenital cataract)

Question 6

Isometropia refers to both eyes having similar ______ error and both eyes having very high rx.

Answer 6

refractive

Question 7

Amblyogenic refractive error due to anisometropia is due to having astigmatism of greater than _____ D, hyperopia of greater than _____ D, and myopia greater than ____ D.

Answer 7

1.50; 1.00; 3.00

Question 8

Amblyogenic refractive error is due to having isometropia when astigmatism is greater than ____ D, hyperopia of greater than _____ D and myopia is greater than _____D.

Answer 8

2.50; 5.00; 8.00

Question 9

Amblyogenic strabismus could be constant vs intermittent, unilateral vs alternating, distance, near/both, or onset before ____years old

Answer 9

8

Question 10

In order for amblyopia to be in full effect, it has be ____, it can’t be alternating at distance/near, it can’t be just at _____

Answer 10

constant, not intermittent; near

Question 11

In order for us rule out form deprivation we need to ask about:

Answer 11

1. congenital/traumatic cataract
2. early complete blepharoptosis (one eye’s visual axis blocked)
3. corneal opacity
4. hyphema
5. vitreous hemorrhage
6. iatrogenic (if patch good eye too much)

Question 12

_____ form deprivation is the worst form.

Answer 12

monocular

Question 13

Binocular form deprivation includes:

Answer 13

1. Dark rearing
2. Binocular lid suture
   - VS remains normal and ready to recover with visual experience.

Question 14

Binocular congenital cataracts cause very mild amblyopia, if removed at 4-6 months of age, VA will be around ____ OU, relatively longer critical period

Answer 14

20/50

Question 15

In monocular deprivation we see structural changes in LGN, there is a smaller size of neurons in layer ____. You also see neuronal shrinkage in deprived parvocellular layers secondary to the striate cortex.

Answer 15

A1

Question 16

Monocular congenital cataracts causes severe amblyopia. If removed at 4-6 months of age, VA will be ____. You have to remove it before ____ months. Deprived can recover up to ____

Question 17

The 2 most common forms of amblyopia are:

Answer 17

1. Strabismic

2. Anisometropic

Question 18

In Strabismic and anisometropic amblyopia there are no structural changes in visual cortex and LGN. They have less profound loss in _____, and usually have better VA.

Answer 18

CSF

Question 19

Why is monocular form deprivation the most severe form of amblyopia?

Answer 19

1. See structural changes in LGN.
2. Worse VA
3. shorter critical dev period
4. reduced CSF
5. Happens in all spatial frequency

Question 20

____ amblyopes often have no CSF loss, but if they do its at high spatial frequencies. _____ amblyopes always have a CSF loss at _____ spatial frequencies, and almost always at have a very small loss at lower frequencies.

Answer 20

Strabismic; Anisometropic; high

Question 21

Isometropic amblyopes have BCVA of greater than or equal to _____ but show wide range from slightly worse than 20/20 to 20/200

Answer 21

20/50

Question 22

Bilateral high hyperopia can cause 3 scenarios:

Answer 22

1. Accommodative esotropia: infant accommodates well and has normal AC/A ratio
2. Bilateral refractive amblyopia: child maintains binocularity by underaccomodating
3. Normal vision: infant accommodates well and has low AC/A ratio

Question 23

In myopic isometropic amblyopia, the CSF has equal sensitivity loss at all _____ ____

Answer 23

spatial frequencies

Question 24

Meridional amblyopia is induced by high astigmatism and has ____ VA loss

Answer 24

mild; develops later due to the presence of astigmatism over a period of years.

Question 25

In anisometropic amblyopia and in normal vision, you see the biggest loss in ____ region. ____ amblyopia shows nasal/temporal asymmetry.

Answer 25

foveal; strabismic

Question 26

What are factors that affect the degree of crowding?

Answer 26

1. Sep between the characters 2. character size 3. location in the visual field

Question 27

Crowding phenomenon is normal for everyone if it is happening in the ____ retina. Amblyopia is happening in central foveal region.

Answer 27

peripheral

Question 28

Amblyopic reading deficit is affected mainly by increased ____ effect, rather than reduced VA. VA with ____ letter yields the best VA

Answer 28

crowding; isolated

Question 29

Possible neural mechanism as to why amblyopes suffer from spatial misperception could be due to neural ____ in the orientation and spatial frequency domains native to the primary visual cortex. Confused _____ detectors may also explain how these different patterns occur.

Answer 29

undersampling; line

Question 30

Fixation for _____ amblyopes is usually central and _____. Fixation for _____ amblyopes is usually eccentric and _____

Answer 30

anisometropic; unsteady | strabismic; eccentric (instead of using fovea they use peripheral point to fixate)

Question 31

Strabismic amblyope eyes usually have from ____ to ____ degrees of eccentric fixation and is measured by maxwell spot or visuoscopy.

Answer 31

0.5; 4

Question 32

Describe how the Maxwell spot measurement is done

Answer 32

Utilizes specific pigmentation around central foveal region causing an entopic phenomenon. It's seen using a cobalt blue filter and is accentuated by first bleaching retina with a green light. The central few degrees will appear darker than periphery. After staring at blue screen and open dot for 15 sec and switching to yellow screen you should see a white spot which means you have central fixation. For strabismic puts they see white spot off to the side.

Question 33

How does visuoscopy work?

Answer 33

You use an opthalmascope with the bulls eye target to look at patients foveal light reflex in patients bad eye, while they are covering their good eye. Normal pt's will have foveal light reflex at center of bulls eye. Strabismic patient's will have light reflex moving around. They will have nasal eccentric fixation.

Question 34

Accommodation appears to be reduced secondary to amblyopia. Pt will experience unsteady and inaccurate accommodation. They will experience high ____ and a lot of ____ motion

Answer 34

lag; with