Pathogenesis of eso- and hypotropia in high myopia

Abstract

In myopia characteristic types of strabismus and defects of ocular motility can occur. One of these myopia related disturbances shows a gradually increasing eso- and hypodeviation in progressively myopic eyes, caused by a corresponding deficit of abduction and elevation. Different pathogenetic factors have been described for this long known clinically uniform entity. In eight patients with pathologic myopia a marked eso- and hypotropia was operated on in the last 15 years. The deviation was infantile in two and acquired in six cases. We performed a routine orthoptic examination and looked for anatomic variations of the rectus muscles during surgery. In seven of the eight cases the anterior portion of the lateral rectus muscle was not directed straight dorsaly but obliquely into the lower temporal quadrant of the orbit. A supraposition of the horizontal recti muscles in addition to a recess-resect procedure provided satisfactory results in five of six cases. Scleral ectasia in high myopia can lead to a downslip of the lateral rectus muscle relative to the globe, giving this muscle a depressing effect at the cost of its physiological action. As in Duane's syndromes with up- or down-shoot, a repair of the deviation is possible by combining horizontal surgery with vertical transposition of the horizontal recti muscles. Additional operations on the vertical recti muscles can thus be avoided.