Background: 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.
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 for anatomic variations of the rectus muscles during surgery.
Results: 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.
Conclusions: 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.