Monocular Nasotemporal Optokinetic Asymmetry—Unraveling the Mystery

Abstract

This article examines the reason why monocular nasotemporal asymmetry (MNTA) is integral in lateral-eyed afoveate animals, and shows how subcortical visual reflexes cause the visual cortex to secondarily reconfigure when the substrate for binocular vision fails to develop within a critical time window. Many pediatric ophthalmologists do not routinely check for MNTA, which is surprising, as I have found it to be a critical determinant of timing of strabismus that often dictates surgical dosing. MNTA readily distinguishes essential infantile esotropia from accommodative esotropia, which requires higher surgical dosing to restore binocular alignment. As clinical overlap can exist (e.g. essential infantile esotropia with an accommodative component), and a parent’s estimate of onset can be misleading, the absence of MNTA suggests that you may need to augment the standard recession. However, it is important to use an optokinetic drum with colored animals rather than stripes to engage a young child’s attention.