Abstract:

Objective To evaluate and compare stereoacuity with respect to refractive error in intermittent exotropia (IXT). Design Retrospective case series. Participants 238 patients with IXT undergoing strabismus surgeries in Beijing Tongren Hospital from Jul 2014 to Aug 2015 were involved. Methods All patients were divided into four groups according to preoperative refractive error: IXT with hyperopia (binocular spherical equivalent (SE)≥+1.00 D ), IXT with emmetropia (-1.00 D＜binocular SE＜+1.00 D), IXT with myopia (binocular SE≤-1.00 D), and IXT with anisometropia (binocular SE difference≥1.00 D). The stereoacuity at distance and near were compared among the four groups. Main Outcome Measures Stereoacuity at distance and near. Results  (1) The mean near deviation of 238 IXT patients was (45.71±18.81)△ and mean distant deviation was (43.98±19.55)△. The ratio of having distant stereoacuity in IXT with hyperopia, IXT with emmetropia, IXT with myopia and IXT with anisometropia were 23.3%, 15.5%, 19.7% and 18.8%. There was no significant different in distance stereoacuity among the four groups. The ratio of having near stereoacuity in IXT with hyperopia, IXT with emmetropia, IXT with myopia and IXT with anisometropia were 66.7%, 79.8%, 81.6%, 64.6%. The near stereoacuity was most serious damaged in IXT with anisometropia while slightest in IXT with myopia. There was significant difference in near stereoacuity between IXT with anisometropia and IXT with myopia (P=0.033). (2) The prevalence of IXT with anisometropia was 20.1%, and myopia anisometropia had highest prevalence while hyperopia anisometropia had lowest prevalence (12.6% vs 1.3%).  (3) The mean difference in SE between each eye in IXT with anisometropia with and without distant stereoacuity were 2.35±0.75 D and 2.34±1.75 D(P=0.21). The mean difference SE in between each eye in anisometropia without near stereoacuity was significantly bigger than in that with near stereoacuity (3.11±2.29 D vs. 1.93±0.83 D, P=0.002). Conclusion For the IXT patients with large deviation, refractive errors have little effect on distant stereoacuity, but anisometropia damages the near stereoacuity. The greater degree of anisometropia, the more serious damage of near stereoacuity occurred. (Ophthalmol CHN, 2016, 25: 396-399)

Key words: intermittent exotropia, refractive errors, stereoacuity