Krimsky test

The Krimsky test measures the angle of strabismus by quantifying the displacement of the corneal light reflex with prisms.^1,2 Prism power is increased until the reflex in the deviating eye is centered, or sits in the same relative position as in the fixating eye, and the prism power needed is the measure of the deviation.^1,3

In the original description the prism goes before the fixating eye, and the examiner sits directly in front of the deviating eye to avoid errors from parallax.^1,2 Many clinicians now find it easier to hold the prism before the deviating eye, and the two placements give identical results unless a secondary deviation is present.^2,4 The test suits children too young for the prism and cover test and patients whose poor acuity prevents adequate fixation, including those with a blind or deeply amblyopic eye.¹

The Krimsky test gives only an approximate measurement, because distance deviations are hard to measure, accommodation cannot be controlled while the patient fixates a penlight, angle kappa is included in the result, and even experienced observers read the reflex differently.¹ Deviations of up to 14 prism diopters may be overlooked.⁴