Why do the eyes cross? A review and discussion of the nature and origin of essential infantile esotropia, microstrabismus, accommodative esotropia, and acute comitant esotropia

Purpose. To try to explain the long-term stability of bilateral medial rectus botulinum toxin (botox) chemo-denervation in essential infantile esotropia; to evaluate divergent fusion amplitude in accommodative esotropia and acute comitant esotropia of emmetropes; to look for accommodation anomalies in high AC/A ratio accommodative esotropia and acute comitant esotropia of myopes; and to discuss characteristics of microstrabismus. Methods. Retrospective analysis of 61 essential infantile esotropia patients with early treatment with one botox injection in both medial rectus; measurement of divergent fusion amplitude in accommodative esotropia and acute comitant esotropia; measurement of Near point of accommodation in high AC/A ratio accommodative esotropia and acute comitant esotropia of myopes. Results. Stable results were found in 85.24% of essential infantile esotropia treated patients; reduced divergent fusion amplitude was detected in accommodative esotropia and acute comitant esotropia; hypo-accommodation was found in some patients with high AC/A ratio accommodative esotropia and a convergence spasm in acute comitant esotropia of myopes. Conclusions. Very early botox treatment probably eradicates the effect of an excessive convergence tonus in essential infantile esotropia. A prevention of accommodative esotropia with full retinoscopic correction is only mandatory with a significantly reduced amplitude of fusional divergence. A deficit in accommodation should be looked for in high AC/A ratio accommodative esotropia, before bifocal lenses prescription. Early diagnosed acute comitant esotropia of myopic patients can be treated as a convergence spasm. Only surgery treats acute comitant esotropia, in patients with emmetropia or moderate hypermetropia.