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A photographic version of the Hirschberg is used to quantify strabismus.
It is performed by shining a light in the persons eyes and observing where the light reflects off of the corneas. In a person with normal ocular alignment the light lands on the centre of both corneas. For an abnormal result, based on where the light lands on the cornea, the examiner can detect if there is an exotropia (abnormal eye is turned out), esotropia (abnormal eye is turned in), hypertropia (abnormal eye higher than the normal one) or hypotropia (abnormal eye is lower than the normal one).
In exotropia the light lands on the medial aspect of the cornea. In esotropia the light lands on the lateral aspect of the cornea. In hypertropia the light lands on the inferior aspect of the cornea. In hypotropia the light lands on the superior aspect of the cornea. A cover test can tell you the extent of the eso/exotropia.
Individuals can suffer from several tropias at once. In Graves ophthalmopathy, it is not uncommon to see an esotropia (due to pathology of the medial rectus muscle) co-morbid with a hypotropia (due to pathology of the inferior rectus muscle).
- Picture of a child with strabismus - medem.com
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