Prevalence and anatomic mechanism of highly myopic strabismus among Japanese with severe myopia.

PURPOSE: To survey the prevalence of highly myopic strabismus among patients with severe myopia and to elucidate its anatomic mechanism.

METHODS: The subjects (mean age 48.5 ± 17.8 years) were 452 Japanese patients (778 eyes) who presented between May 2011 and April 2012 and were diagnosed as severely myopic (objective refractive error ≥-6.00 D or axial length ≥ 27 mm). For diagnosis, the eye position at 0.33 m, axial length, and diagnostic positions of gaze were determined; magnetic resonance imaging (MRI) was also used.

RESULTS: Sixteen eyes of 9 patients fulfilled the disease criteria, and strabismus fixus was observed for 3 eyes of 3 patients. Disease prevalence was 2.65 %. The mean age of the 12 patients was 65.5 ± 17.9 years. For 18 eyes for which the axial length could be measured, mean axial length was 28.9 ± 2.03 mm. For the 16 eyes examined by MRI the mean dislocation angle was 132° ± 14.0°. The axial length was 26 to <30 mm for 13 of the 16 eyes, dislocation angle was 110° to <150° for 14 eyes, and both axial length and dislocation angle were within these ranges for 12 eyes.

CONCLUSIONS: The prevalence of the disease was 2.65 %. However, this was not a general epidemiological survey and the screening criteria did not adequately cover all disease cases. In addition, even for eyes that are still mildly-moderately myopic, this disease can develop in the presence of orbital pulley abnormalities.