METHODS:A retrospective study. Thirty patients(60 eyes)with refractive regression after LASIK in our hospital from January 2016 to January 2018 were selected for statistical analysis. According to preoperative refraction, they were divided into three groups: moderate myopia group(<-6.00D), high myopia group(-6.00 to -10.00D)and super high myopia group(>-10.00D). The visual acuity, diopter, corneal curvature, CCT, intraocular pressure, ocular axis and residual corneal matrix thickness were analyzed before and after surgery.

RESULTS:The refractive regression rate was 8.6%(60/700 eyes). At 6mo after operation, the refractive regression of the patients were as follows: moderate myopia group, 1.31±0.15D, high myopia group, 1.76±0.23D, ultra-high myopia group: 2.53±0.35D(P<0.05). At 6mo after operation, the diopter(-0.82±0.21, -1.03±0.27, -1.57±0.52D)of the three groups was different from that of the preoperative(-4.87±0.97, -7.46±1.03, -10.32±2.01D)and 1mo(+0.49±0.22, +0.73±0.17, +0.95±0.15D)after operation(all P<0.05). At 6mo after operation, the CCT of the three groups(499.80±33.78, 458.89±36.93, 451.93±24.52μm)decreased(P<0.05)compared with that before operation(523.80±23.00, 527.24±25.47, 525.80±22.36μm), and increased(487.92±38.13, 440.65±33.92, 429.35±20.14μm). There was no difference in ocular axis(25.25±0.30, 26.52±0.62, 28.63±0.21mm)between the three groups at 6mo after operation and before operation(25.13±0.54, 26.13±0.54, 28.03±1.04mm)(P>0.05), but there was difference between the two groups(P<0.05). The thickness of residual corneal stroma in moderate myopia group, high myopia group and ultra-high myopia group were 332.27±21.87, 292.71±22.71 and 273.38±20.99μm, respectively(P<0.05). There was no difference in corneal curvature and intraocular pressure between the three groups at 6mo after operation(P>0.05).

CONCLUSION: The occurrence of refractive regression after LASIK is related to preoperative refraction. High myopia and ultra-high myopia may have refractive regression due to progressive growth of eye axis, while moderate myopia may have refractive regression due to increased corneal thickness and corneal curvature changes caused by post-operative matrix repair.