An Expanded View of Infantile Esotropia

Abstract

A recent editorial in the Archives assigned the primary pathogenesis of infantile esotropia to the visual cortex. This analysis addresses the limitations of this timeworn view and advances the perspective that infantile esotropia is a cortico-mesencephalic-cerebellar disorder wherein binocular cortical maldevelopment permits atavistic subcortical visual pathways to remain operational. This integrated neuroanatomical model predicts that primary neurodevelopmental disorders involving the accessory optic system or its connections to the cerebellum can also give rise to infantile esotropia.

The Optokinetic Uncover Test

“…Fifth, the ability of subcortical visual pathways (Figure 2) to be activated bidirectionally via subcortical and cortical visual pathways would render obsolete the debate about neuroanatomical localization in infantile esotropia. 3 This study has several inherent limitations. First, we did not use a circular full-field optokinetic apparatus, which produces the sensation of circularvection (the false sensation of physical rotation) and is believed to be necessary to directly stimulate the visuovestibular system.…”

“…2 This constellation of findings is also seen in the setting of prematurity and other neurological disorders. 3 Patients with infantile esotropia retain a monocular nasotemporal optokinetic asymmetry (MNTA) characterized by brisk monocular optokinetic responses to nasally moving optokinetic targets and poor monocular optokinetic responses to temporally moving optokinetic targets. [4][5][6][7][8] The phenomenon of MNTA is believed to underlie latent nystagmus.…”

“…Because MNTA antedates development of the visual cortex both phylogenetically and ontogenetically, debate has been waged as to whether the persistent MNTA in humans with strabismus is caused by a cortical pursuit defect, a persistent activation of subcortical optokinetic pathways, or a combination of both. 3,8,10,19,25 Cortical pursuit movements in foveate animals require foveal (or perifoveal) stimulation, while subcortical optokinetic movements in afoveate animals are generated by full-field optic flow detected by peripheral retina. 26 If the persistence of MNTA in humans with infantile strabismus is caused solely by defective cortical pursuit, its activation should necessitate foveal (or parafoveal) fixation.…”

Essential Infantile Esotropia: Potential Pathogenetic Role of Extended Subcortical Neuroplasticity

“…[15][16][17][18] Both phylogenetically and ontogenetically, MNTA antedates development of the binocular visual cortex. 6,11,12 In lateraleyed animals, MNTA may help to prevent temporalward optokinetic stimuli from pinning the eyes back as the animal is moving forward. 13,14,19 However, another unrecognized evolutionary advantage conferred by this reflex derives from the fact that the nose and mouth are always ''nasal'' to the eyes, necessitating accurate nasalward optokinetic tracking as the animal turns toward potential food substances seen by either eye.…”

“…Its prominent association with binocular torsion, which is conspicuously absent in isolated lesions involving the visual cortex, provides further evidence that EIE is generated within the subcortical prenuclear ocular motor pathways. 6…”