The estimation of binocular imbalance based on objective examination of the eyes has been found unsatisfactory because inspection of the eyes in a routine examination of the muscles is often difficult. The role of the corneal light reflex as an aid in clinical practice has not been sufficiently explored, and my aim in this paper will therefore be to show how this reflex can be utilized clinically to complement the familiar cover test.
First, as to the meaning of the fixational corneal light reflex : For practical purposes it may be regarded as the constant position of the light reflex on the cornea when the eye is made to fix a light and when the observer's eye is behind the testing light. It may not be on the center of the cornea (angle gamma), even though the macula assumes fixation, but it represents the normal anatomic position of the light reflex
KRIMSKY E. FIXATIONAL CORNEAL LIGHT REFLEXES AS AN AID IN BINOCULAR INVESTIGATION. Arch Ophthalmol. 1943;30(4):505–520. doi:10.1001/archopht.1943.00880220097010