Answer: This is a test for determining if the eyes are in alignment, typically done in young children who may be hard to do fomal cover testing. You shine a light at the eyes and observe where the light reflex is located in referrence to the pupil.
In general, for every mm that the light is decentered, the eye is turned about 15 diopters (7 degrees from center).
This is obviously not the most accurate method for measuring strabismus, but sometimes this is all you can get. There are cases where the Hirschberg seems abnormal, but the patient doesn’t have strabismus. For example, if a patient has a temporally dragged macula (this can occur from retinopathy of prematurity) then their eye may have to turn slightly outward to center the vision. Thus, they “appear” exotropic, but the cross-cover test shows everything is fine.
Confused, yet? Don’t worry, as tropias and phorias can be difficult, which is why we have pediatric and neuroophthalmology sub-specialties!
Comments and Feedback
1 Comment
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its has few but very very important two points. the info is really very useful.
Comment by maria — January 14, 2010 @ 9:11 am
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