Strabismus/Amblyopia Diagnosis

Question 1

Name 4 ways to assess Monocular Fixation

Answer 1

1. Angle Kappa:
   -Have patient fixate a penlight @40cm (observer should be positioned with one open eye at the patients midline). Cover one eye and observe the corneal reflex - estimating the displacement from the center of the pupil. Switch eyes. Record displacement in mm.
   (+) = nasal displacement of corneal reflex
   (-) = temporal displacement of reflex
   Calculate Eccentric Fixation 1mm = 22pd
2. Visuoscopy
   -Most reliable and sensitive method for assessing monocular fixation.
   -Setting on ophthalmoscope
   -Occlude amblyopic eye and have patient fixate the center target
   -Occlude good eye and place target on retina of amblyopic eye. Have patient fixate the center of the target. If fovea is placed inside center circle then no EF is noted.
3. Haidinger’s Brush - uses entopic phenomenon
   -Requires special equipment
   -The brush location marks the position of the patients fovea. If the brush is over the fixation point then the patient does not have EF.
4. Brock-Givner After-Image Transfer
   (assumes normal retinal correspondence)
   -Good eye is tagged with vertical afterimage (if NC - then the fovea of the amblyopic eye will see the AI)

Question 2

Which test is extremely useful in the detection and diagnosis of small angle ocular deviations?

Answer 2

The Bruckner Test
-Dim room, @ 50-80cm, use ophthalmoscope focused on patients face, note position of the corneal reflexes (basically hirschberg), note pupil size and relative color/brightness of each fundus. Examiner can cover an eye to look for changes in the above.

Question 3

Name 4 tests to determine the presence/magnitude of an ocular deviation

Answer 3

1. Hirschberg + (Kappa is needed to determine which eye fixates)
2. Bruckner Test
3. Krimsky Test (use estimated magnitude determined in Hirshberg)
4. Cover Test - remember neutralization of the ACT is done with the nonstrabismic eye fixating and then the strabismic eye fixating.