Correlation analysis and corneal flap thickness changes among Moria SBK,90 and 110 microkeratome in laser in situ keratomileusis

Background The average thickness and variation of corneal flap are very important to laser in situ keratomileusis(LASIK)because it is related to the predictability and safety of the surgery.ObjectiveThis study was to analyze the change of corneal flap thickness with Moria SBK,90 or 110 microkeratome after LASIK and identify the relevant factors to the flap thickness.MethodsDifferent corneal flaps were made with Moria SBK,90 or 110 microkeratome during the LASIK in bilaterial eyes of 30 patients separately and then divided into SBK microkeratome group,90 microkeratome group and 110 microkeratome group.Flap thickness was calculated by measuring the corneal stromal bed thickness.The change of flap thickness was analyzed and compared among these three groups.The relationship of flap thickness with age,refraction,preoperative corneal thickness,keratometry and diameter were evaluated.Informed consent was obtained from all participants before surgery.ResultsNo significant differences were found in age,refraction,corneal thickness,corneal horizontal diameter,cornea curvity among the three groups before LASIK(P0.05).In SBK microkeratome group,the corneal flap thickness was 97.50±11.39μm in the right eyes and 96.73±10.45μm in the left eyes separately without significant difference(t=0.790,P=0.440).The regression analysis revealed that flap thickness had a positive correlation with corneal thickness(r=0.490,P=0.000)and a negative correlation with corneal diameter(r=-0.520,P=0.002)or with age(r=-0.360,P=0.0023).In 90 microkeratome group,the corneal flap thickness was 128.03±12.03μm and 123.40±12.38μm separately in the right eyes and left eyes with a statistically significant difference(t=2.890,P=0.007).In 110 microkeratome group,the corneal flap thickness was 140.53±15.14μm and 135.23±18.03μm separately in the right eyes and left eyes,showing a.statistically significant difference(t=3.180,P=0.004).The flap thickness was positive correlated with preoperative corneal thickness(r=0.710,P=0.000).ConclusionCorneal flap thickness made by MORIA microkeratome is associated with preoperative corneal thickness.The least variation in flap thickness is SBK and the most one is 110 microkeratome.SBK and M2 90 microkeratome are more beneficial in making the ultrathin and thin corneal flap.Intraoperative corneal pachymetry should be measured to adjust the treatment regimen and avoid postoperative secondary keratoconus during the LASIK.