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Characteristics of Refractive Error as a Function of Age in a Korean Population
Purpose: To investigate the pre-operative and post-operative objective optical quality after overnight orthokeratology (ortho-k). Methods: Twenty two patients (43 eyes) satisfying the inclusion criteria (myopia < -4.50 D, astigmatism < -1.50 D, K-reading: 40.00 ~ 46.75 D) for overnight ortho-k. Visual acuity (VA) was measured by using System Chart (SC-2000, Nidek). Objective optical quality measurements were performed using the Optical Quality Analysis System (OQAS Visionmetrics SL, Spain) for modulation transfer function (MTF), strehl ratio, and objective scattering index (OSI). Statistical analyses were performed with SPSS 18.0 (SPSS Inc, Chicago, Illinois) and p value less than 0.05 was considered statistically significant. Results: The MTF values were 42.61 ± 8.39 pre-operatively, and 37.88 ± 11.77 post-operatively that there was no significant difference (p = 0.075). The strehl ratios were 0.24 ± 0.08, and 0.20 ± 0.05, respectively that there was significant difference between pre- and post-ortho-K (p = 0.001). OSI value were 0.37±0.17 and 0.71 ± 0.37, respectively, which were statistically significant (p < 0.000). According to OSI values, the mean value of VA was 0.05 ± 0.06 logMAR in the over 0.40 OSI group and 0.01 ± 0.05 logMAR in the less 0.40 OSI group that there was no significant difference (p = 0.085). Conclusions: There were no significant difference in the objective visual quality such as MTF between pre- and post-ortho-K. The postoperative Strehl ratio was decreased and OSI value was increased significantly compared with pre-operation, however, increase in the OSI would not influence on the UCVA.
