This is an example of the Bruckner test which is one of the "light-reflex" tests used to diagnose strabismus. This test is typically used by primary care physicians (e.g. pediatricians) to grossly screen for strabismus. If strabismus is present, then the deviating eye will have a lighter and brighter red reflex compared to the fixating eye. The Bruckner test is also used to screen for media opacities (e.g. cataract, vitreous hemorrhage) as well as anisometropia.