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SL Fawcett, WK Herman, KA Castleberry, MM Parks; LASIK Monovision For Presbyopia Results in an Uncorrectable Loss of Foveal Binocular Vision . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2943.
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Purpose: Adults with longstanding surgical monovision exhibit deficient stereopsis following full binocular refractive correction (Fawcett et al., 2001, J'AAPOS). To quantify changes of binocularity that result directly from surgical monovision, baseline measurements are necessary. In a prospective and longitudinal study, we investigated whether adults with presbyopia undergoing LASIK monovision exhibit an uncorrectable loss of binocular vision. Methods: 22 adults with presbyopia (age 41-61 yrs) undergoing LASIK monovision were enrolled. Binocular vision was measured prior to LASIK and at 12-24 months post-LASIK with and without full binocular refractive corrections. Random dot stereoacuity was measured using Randot Stereoacuity Tests. Foveal fusion was measured using the Worth 4-dot test at 3 meters. Results: Two Way Repeated Measures MANOVA on One Factor demonstrated significant main effects of treatment (F = 40.36, p<.001) and anisometropia (F = 5.90, p<.02) on stereoacuity and a significant interaction between treatment and anisometropia (F = 10.26, p<.001). Mean stereoacuity before treatment was 60 sec. Treatment with LASIK monovision produced a deficiency of stereopsis (mean 277 sec, p=.001) that remained following full binocular refractive correction (mean 122 sec, p=.001). Patients with high anisometropia produced by LASIK (≷1.5 diopters) had significantly worse stereoacuity (mean 258 sec) than patients with low anisometropia (mean 104 sec). Anisometropia also had a significant effect on sensory foveal fusion. 80% of patients with low anisometropia passed the Worth 4-dot test compared to 15% of patients with high anisometropia (Fisher Exact Test, p=.007). Conclusion: Uncorrectable deficiencies of high-grade stereopsis and foveal fusion may occur as a result of LASIK monovision. These deficiencies of foveal binocular vision are present in patients with LASIK-induced low and high anisometropia, however, they tend to be greatest among patients with high anisometropia. These observations demonstrate plasticity and continued susceptibility for the development of monofixation syndrome in adults. Whether the adult binocular visual system maintains plasticity to recover from a loss of foveal binocularity is under investigation.
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