NBEO Ocular Motility Practice Test

Caloric testing depends on temperature-induced convection in the horizontal semicircular canal to create endolymph flow and stimulate the vestibular system, so we can observe the resulting nystagmus and compare the ears.

Using both cold and warm water provides robust, directional responses and allows a side-by-side comparison. Cold water makes nystagmus beat toward the opposite ear, while warm water makes it beat toward the irrigated ear. This opposite-versus-same effect (often remembered as COWS: Cold Opposite, Warm Same) helps identify which ear is functioning properly and detect unilateral vestibular weakness. Water is the classic stimulus because it produces strong, controllable endolymph movement; air irrigation can be used in some settings but is not the standard two-temperature stimulus for the diagnostic caloric test.