stereo/diplopia

Question 1

word problem CT for EP

Answer 1

when the paddle is moved, the previously covered eye will move out

the covered eye will move behind the paddle on unilateral cover test

Question 2

Hirschberg

Answer 2

measure of gross alignment. the Patient views a light source held at 50cm on his midline. The examiner observes the corneal reflex and each eye compared to the pupillary axis

Question 3

what is considered normal for Hirschberg

Answer 3

0.5mm nasal

Question 4

angle lambda

Answer 4

what is measured on Hirschberg under monocular conditions

normal is 0.5mm nasal

Question 5

1mm shift in the corneal light reflex

Answer 5

22PD

Question 6

contour stereo testing

Answer 6

monocular clues
a patient without stereopsis could still do well
uses laterally displaced targets with monocular cues
-titmus fly, wirt circles, animals
-better at detecting peripheral stereopsis

Question 7

global stereo testing

Answer 7

random dot targets that have NO monocular cues ( the patient must have bifocal fixation to detect shapes within random dot targets.) These targets are very good for detecting constant strabismus

must have bifocal fixation to appreciate

Question 8

normal stereopsis

Answer 8

20s of arc with contour testing and an appreciation for gross random dot targets

Question 9

phi

Answer 9

subjective CT

-ask the direction they see the target move

Question 10

anismetropic amblyopia

Answer 10

due to a significant difference in uncorrected refractive error between the two eyes

Question 11

anisometropic hyperopia vs anisometropic myopia

Answer 11

aniso hyperopia is more likely to lead to amblyopia. In myopia, each eye will have a clear retinal image at some distance, reducing the risk of developing amblyopia (although stereopsis will still be decreased because the eyes never learn to work together). In contrast, in hyperopia, the eye will accommodate the smallest amount possible in order to obtain a clear image, resulting in the less hyperopic eye having a clear retinal image while the more hyperopic eye ALWAYS has a blurred retinal image

Question 12

isometric amblyopia

Answer 12

due to high refractive error in BOTH eyes. BC the refractive error is so high, neither eye receives a clear retinal image, resulting in poor connections between each eye and the visual cortex

Question 13

meridional amblyopia

Answer 13

characterized by reduced acuity for stimuli in a certain orientation due to uncorrected astigmatism during the critical period. The reduced acuity persists even after correction of the astigmatism

Question 14

how should glasses be worn to reduce the risk of amblyopia

Answer 14

full time

Question 15

anisometropic myopia value

Answer 15

> 3D

Question 16

isometropic myopia value

Answer 16

> 8D

Question 17

anisometropic hyperopia value

Answer 17

> 1D

Question 18

isometropic hyperopia value

Answer 18

> 5D

Question 19

anisometropic astigmatism value

Answer 19

> 1.50D

Question 20

isometropic astigmatism value

Answer 20

> 2.50D

Question 21

mallet box

Answer 21

binocular cues for motor fusion and therefore measures the associated phoria (fixation disparity) . the majority of the field of view is seen by both eyes, which serves as a fusion lock to prevent the eyes from dissociating.

Question 22

associated tests

Answer 22

mallet box 
AO vectograph 
Bernell lantern
Wesson fixation card 
Sheedy disparameter 

used for FD

Question 23

decompensated phoria

Answer 23

a large phoria that the patient can no longer compensate for, resulting in an acute intermittent or constant tropia that causes diplopia

Question 24

ARC

Answer 24

develops prior to the age of 5 in patients with a constant unilateral strabismus. The fovea f of the non deviated eye becomes linked to a new retinal point fn of the deviated eye so that the image seen by both eyes is in the same visual direction. This adaptation prevents diplopia and visual confusion

Question 25

congenital nystagmus

Answer 25

present at birth or before the age of 6. it generally does not cause complaints of oscillopsia that can be seen with acquired cases of nystagmus

Question 26

saccadic suppression

Answer 26

occurs when the visual cortex suppresses vision during a saccade in order to minimize image blur, Suppression prevents diplopia and oscilopsia

Question 27

fixation disparity

Answer 27

measured in minutes of arc
the small misalignment of the visual aces of the two eyes under associated conditions, meaning it DOES NOT cause diplopia. Although there is a small misalignment of the eyes, the object falls within Panums Fusional Area for the corresponding retinal points in each eye, resulting in the object being seen as single

Question 28

horopter

Answer 28

image here is single

Question 29

panums

Answer 29

slightly behind/infront of the horopter but still single image

Question 30

when is fixation disparity indicated

Answer 30

if the patient has symptoms of asthenopia but no complaints of diplopia. If a fixation is noted, prism can be prescribed to neutralize the small ocular misalignment. The magnitude of prism necessary to neutralize the fixation disparity is termed the associated phoria. Clinically, the smallest amount of prism that is necessary to relieve the patient symptoms is prescribed

Question 31

type 1 FD curve

Answer 31

most common with a sigmoidal shape, patients are asymptomatic
“large comfy chair”

Question 32

type 2 FD curve

Answer 32

due to an eso disparity

Question 33

type 3 FD curve

Answer 33

due to an eco disparity

Question 34

type 4 FD curve

Answer 34

unstable BV system. Patients may not have ab associated phoria but may have symptoms of aniseikonica and poor sensory fusion

Question 35

a FD that is opposite direction to the associated phoria

Answer 35

paradoxical fixation disparity