Can You "Look" Through a Blind Eye? If So, What Happens?

Manifest latent nystagmus (MLN) is a jerk nystagmus with a decreasing-velocity or linear slow phase whose fast phase is in the direction of the fixating eye. Change of the fixating eye by alternating tropias or cover will cause reversal of the MLN to preserve this relationship. In the dark, where no fixation is possible,- the direction of MI^ is in the direction of the intended fixating eye; actual visual input will override this effect of intention. We recently studied a patient with monocular persistent hyperplastic primary vitreous of the right eye which was enucleated at age 12 due to glaucoma. He had MLN with fast phases to the left since his right eye was congenitally blind; he had a prosthesis in that eye whose movements were conjugate with his seeing eye. Recordings showed remarkable conjugacy, even at the level of subtle nuances in saccadic trajectories, and a bilateral internuclear ophthalmoplegia, more prominent in the right eye than in the left.