Each plane glass lens has fine parallel striations inscribed onto the surface orientated at 45 degrees on one lens and 135 degrees on the other. A spotlight is converted into a line image seen at 90 degrees to the striations when viewed through the lenses. The test is useful with differential diagnosis when patients present with a slight - moderate unilateral reduction in visual acuity that does not improve with a pinhole. Some patients with this type of presentation will have a small angle strabismus that is not detectable using the cover test (microtropia with identity). Proving the existence of anomalous retinal correspondence will help rule out sinister causes for the reduction in visual acuity. It is not a routine test and only warranted when investigating the level of binocularity of patients with a heterotropia.
Shine a Visuscope beam target through the pupil of the suspect eye and cover over the patient’s good eye with a hand. Focus the Visuscope target on to the retina and ask the patient to look at the centre of this target. Compare the position of patient’s foveal reflex with the centre of the target...
This test provides further information about the vergence system and is especially useful for those patients that have with symptoms associated with near work.
