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C.E. Joslin, J. Koster, E. Tu; Corneal Refractive Power Post Refractive Surgery . Invest. Ophthalmol. Vis. Sci. 2004;45(13):308.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Corneal refractive power post–LASIK is difficult to estimate, frequently resulting in unpredictable refractive results after cataract surgery. The historical method is currently the gold standard, but few accurate alternatives exist if this is unavailable. Rigid contact lens overrefraction (CLO) is a method to estimate corneal power that has been suggested, but the accuracy of this method has not been verified. Methods:Twenty eyes of 10 subjects who underwent myopic LASIK were included in this case series. The accuracy of CLO was compared to the clinical history method in predicting the corneal refractive power. The CLO from four different rigid lenses fit based on corneal topography patterns were compared and analyzed. The four different rigid lens fits included 9.0 mm overall diameter lenses fit flat, steep, and an average of the two, and also a 15.0 mm overall diameter lens fit steep. A cyclopleged CLO was performed using the autorefractor function of the OPD (Nidek, Japan). Results for each lens were analyzed at three different pupil scan sizes (3–mm, 5–mm, and total pupil). The Pearson’s product–moment correlation coefficient was used to compare the resultant CLO from the various rigid lens fits to the clinical history method. A paired, two–tailed t–test was used to test for statistical significance. Results:The corneal power estimated with the CLO method varied based on lens fit. Corneal power estimated with a flat fitting, 9.0 mm lens had the poorest correlation with and was statistically significantly different than the historical method (r = 0.74, p = 0.0009). In comparison, the 15.0 steep fitting lens had the best correlation and there was no significant difference between the CLO and historical method in estimating the corneal refractive power (r = 0.96, p = 0.25). With the flat fitting, 9.0 mm lens, only 25% and 13% of the eyes were within 1.00 D and 0.50 D, respectively, of the power predicted by the historical method. In comparison, 95% and 65% of the eyes were within 1.00 D and 0.50 D, respectively, with the 15.0 mm lens. The corneal refractive power predicted using the CLO method also varied based on the OPD pupil scan size for each lens used except the 15.0 mm lens. Conclusions:This pilot work demonstrates that rigid CLO has the potential to accurately and precisely predict corneal refractive power in post–refractive surgery eyes. Additional research is necessary to refine this method of estimating corneal refractive power and to examine its accuracy in post–refractive surgery eyes that are undergoing cataract surgery.
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