ON THE PATHOGENESIS OF LARGE ESOTROPIA AND HYPOTROPIA IN A PATHOLOGICAL MYOPIA

Background In myopia characteristic types of strabismus and defects of ocular motility can occur. One of these myopia related disturbances s hows a gradually increasing eso- and hypodeviation in progressively my opic eyes, caused by a corresponding deficit of abduction and elevatio n. Different pathogenetic factors have been described for this long kn own clinically uniform entity. Patients and Methods 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 fo r anatomic variations of the rectus muscles during surgery. Results In seven of the eight cases the anterior portion of the lateral rectus m uscle was not directed straight dorsaly but obliquely into the lower t emporal quadrant of the orbit. A supraposition of the horizontal recti muscles in addition to a recess-resect procedure provided satisfactor y results in five of six cases. Conclusions Scleral ectasia in high my opia can lead to a downslip of the lateral rectus muscle relative to t he globe, giving this muscle a depressing effect at the cost of its ph ysiological action. As in Duane's syndromes with up- or down-shoot, a repair of the deviation is possible by combining horizontal surgery wi th vertical transposition of the horizontal recti muscles. Additional operations on the vertical recti muscles can thus be avoided.