This is the Bruckner test, and the left eye is the deviating eye. The test lights up both pupils at the same time with a direct ophthalmoscope so you can compare the two red glows side by side. The eye that holds fixation gives the duller, darker glow. The eye that is turned gives the lighter, brighter glow. Here the right glow is duller, so the right eye is fixing on the light. That leaves the brighter left eye as the turned, or deviating, eye.
Two features make this test useful in a young child. It is fast and it needs no response from the patient. It also screens for anything that blocks the line of sight, such as a cloudy lens, because that eye's glow goes dim or dark. Other light tests work in a different way. The Hirschberg method shines a penlight and reads where the corneal light reflex sits in each pupil. Centered reflexes mean straight eyes. Each 1 mm the reflex is off center stands for about 7 degrees, or 15 prism diopters, of turn. The Krimsky method adds prisms until the off-center reflex moves back to the pupil center, which measures the turn.
The rule to carry in is short: brighter glow, turned eye. Then confirm any eye turn with cover testing, which is less easily fooled. Telling these screening tests apart is a core part of the COA ocular motility content area.
Incorrect Answers
- C. The Hirschberg method uses a penlight and the corneal reflex, not a red glow seen through an ophthalmoscope.
- D. The right glow was the duller one, so the right eye is holding fixation, not deviating.
- E. The Krimsky method needs prisms held in front of the eye to balance the corneal reflexes. No prism was used here.
Testing Pearls
- The Bruckner test compares both red glows at once and needs no answer from the child.
- A brighter red glow points to the deviating eye; the duller glow is the fixing eye.
- A dark or absent glow suggests something blocking the line of sight, such as a cloudy lens.
- Hirschberg: 1 mm of reflex shift is about 7 degrees or 15 prism diopters.
- Krimsky is Hirschberg plus prisms, so it measures the turn.
References
- American Academy of Ophthalmology. Ophthalmic Medical Assisting: An Independent Study Course. Chapter 9, Ocular Motility.
- American Academy of Ophthalmology. Ophthalmic Medical Assisting: An Independent Study Course. Chapter 8, Comprehensive Medical Eye Examination.
