In the Krimsky test, what determines which prism direction is used to neutralize the deviation?

• A. The magnitude of the deviation
• B. The direction of corneal reflex displacement
• C. The refractive error
• D. The age of the patient

Answer: (B)

The key idea tested is using the corneal light reflex to guide prism placement in the Krimsky test. You observe where the corneal reflex (the Hirschberg point) sits in each eye when the patient fixes on a target. The way the reflex in the deviated eye shifts relative to the pupil tells you how the eyes are misaligned and, crucially, which way to tilt the light beam with a prism to bring the eyes into alignment. You then adjust a prism in front of the fixing eye and change its direction so that the corneal reflections coincide. The actual amount of prism you need depends on how large the deviation is, but the direction you choose comes from the observed displacement of the corneal reflex. Refractive error or age don’t determine which prism direction to use.