Acquired Concomitant Esotropia in Myopia with Excessive Near-distance Work

Abstract

　There are two types of esotropia with myopia. The first is highly myopic strabismus that shows eyeball prolapse from the muscle cone on orbital magnetic resonance imaging（MRI）, and the other is an acquired concomitant esotropia in myopia that does not show eyeball dislocation. The orbital opening angle can be measured on the axial slice of orbital MRI. The orbital opening angle in patients with highly myopic strabismus is larger than that in patients with acquired concomitant esotropia in myopia. Thus, the orbital bone shapes and the pathogenic mechanism of these two types of esotropia are considered to be different.

　The causative factors for the onset of acquired concomitant esotropia in myopia remain unknown, yet the incidence of acquired concomitant esotropia has recently been increasing,especially in teenager and young adults. Acquired concomitant esotropia in myopia is a form that exhibits many similarities to acute acquired concomitant esotropia（AACE）, however, it onset is“insidious”rather than“acute”. A typical case of acquired concomitant esotropia in myopia initially presents with intermittent diplopia at only far distance. As it gradually progresses, the distance at which the patients show diplopia becomes shorter, eventually causing constant strabismus. Patients with acquired concomitant esotropia in myopia often have uncorrected or under-corrected refractive error, and it is speculated that the onset is caused by excessive neardistance work at close viewing distances and lifestyle habits that don’t focus on distance objects.