Hirschberg test is also known as the Hirschberg corneal reflex test. This test is done to determine if squint (strabismus) is present.
To perform the Hirschberg test, the doctor shines a penlight on the eye from a distance of about 50 cm and observes the position of the light that reflects off the cornea (corneal relax). If there is no squint, the reflection will be at the centre of the pupil. If there is squint, the light reflex in the eye will be situated away from the centre of the pupil. The position of the corneal reflex away from the centre of the pupil can be used to determine the type of squint.
- In esotropia, the corneal reflex is temporal to the centre of the pupil
- In exotropia, the corneal reflex is nasal to the centre of the pupil
- In hypertropia, the corneal reflex is below the centre of the pupil
- In hypotropia, the corneal reflex is above the centre of the pupil
The degree of deviation can also be measured using an appropriate loose prism to move the reflection of the light to the centre of the pupil. Alternatively, the distance between the corneal reflex and the centre of the pupil in the deviating can be measured and converted to the degree of deviation or squint. I mm of deviation is equal to 22 prism diopters.