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J. J. Castro, J. R. Jiménez, E. Hita, R. G. Anera; Maximum Disparity After Lasik. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5645.
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To evaluate stereoscopic vision after LASIK and the role of post-surgical interocular differences in higher-order eye aberrations, corneal asphericity, and initial anisometropia.
We measured maximum disparity with a mirror stereoscope pre-(best-corrected) and after LASIK for 30 patients. Their mean pre-operative spherical refractive error was -4.7±2.0 D, ranging from -1.0 to -8.0 D. Data on aberrometry were taken with a WASCA aberrometer. Corneal shape data were provided by a corneal topographer. For each patient, the anisometropia was computed as the difference between the spherical equivalent of each eye.
The results showed that stereoscopic vision is less effective after LASIK, since for 93% of the patients, maximum disparity diminished. This lower maximum disparity implies a reduction in the physical region where stereoscopic perception occurs and thus in the quality of stereopsis. We also found that the larger the interocular-differences in post-surgical corneal asphericity the less effective the stereopsis (r=0.82, p<0.01); on the other hand, the greater the differences in the higher-order aberrations, the worse the quality of stereoscopic vision (r=0.85, p<0.01). Analyzing pre-LASIK anisometropia we found that maximum disparity diminishes for increasing values of initial anisometropia (r=0.87, p<0.01).
Our results indicate that stereopsis deteriorates after LASIK. Ablation algorithms should minimize interocular-differences (aberrations and corneal aasphericity) to avoid a decrease in binocular visual performance.
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