In a person with normal ocular alignment the light reflex lies slightly nasal from the center of the cornea (approximately 11 prism diopters—or 0.5mm from the pupillary axis), as a result of the cornea acting as a temporally-turned convex mirror to the observer.

When doing the test, the light reflexes of both eyes are compared, and will be symmetrical in an individual with normal fixation.

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).

The Krimsky test is essentially the Hirschberg test, but with prisms employed to quantitate deviation of ocular misalignment by determining how much prism is required to centre the reflex.

The technique was developed by German ophthalmologist Julius Hirschberg who in 1886 used a candle to observe the light reflex in an eye with strabismus.