[Comparison of the effects of different side-cut angles on corneal biomechanical properties after femtosecond laser assisted-laser in situ keratomileusis].
Objective:To evaluate the effects of side-cut angles on corneal biomechanical properties after femtosecond laser assisted-laser in situ keratomileusis (FS-LASIK).Methods:In this clinical control study, 97 right eyes of 97 patients with myopia and myopic astigmatism undergoing FS-LASIK surgery were included randomly. Two types of side-cut angles were designed for the flap, 90° in 48 eyes and 130° in 49 eyes. The values of corneal resistance factor (CRF), cornea hysteresis (CH) and 37 biomechanical waveform parameters were measured using the ocular response analyzer preoperatively and at 1 and 3 months postoperatively. The comparison between the two groups at different follow-up time points was made with one-way analysis of variance, and the comparison among different follow-up time points in each group was performed with the repeated measures analysis of variance.Results:The mean CRF, CH, p area, h, dive1, dive2, w11 and w21 in both groups showed significant reduction at 1 month postoperatively (group 90°: CRF 10.49vs.6.85, CH 10.02vs.7.55, p1 area 3 537.54vs.1 918.07, h1 404.74vs.283.25, dive1 350.63vs.243.33, w11 10.50vs.7.58. group 130°: CRF 10.14vs.6.38, CH 9.93vs.7.13, p1 area 3 498.93vs.2 038.74, h1 411.93vs.304.49, dive1 352.51vs.265.12, w11 10.55vs.7.78.P<0.001) . The mean CRF, CH, p area, w, h, dive1 and dive2 in both groups showed significant reduction at 3 months postoperatively (group 90°: CRF 10.49vs.6.60, CH 10.02vs.7.65, p1 area 3537.54vs.2042.91, h1 404.74vs.307.77, dive1 350.63vs.263.33, w11 10.50vs.7.58. group 130°: CRF 10.14vs.6.45, CH 9.93vs.7.67, p1 area 3 498.93vs.2 187.97, h1 411.93vs.327.39, dive1 352.51vs.284.26, w11 10.55vs.7.61.P<0.001). The mean path in both groups showed significant increase at 1 and 3 months postoperatively (group 90°: path1 23.14vs.30.50vs.30.79. group 130°: path1 24.12vs.32.18vs.31.49.P<0.001). The mean aplhf, bindex, dive2 and path2 between both groups at 1 month postoperatively showed significant difference (F=8.609, 7.482, 5.238, 4.885,P<0.05). The mean path11 between both groups at 3 months postoperatively showed significant difference (F=6.160,P<0.05).Conclusions:Corneal biomechanical properties significantly decrease after FS-LASIK, and different side-cut angles have some effect on corneal biomechanical properties after FS-LASIK. The corneal deformation is more stable after flap creation with an obtuse side-cut angle making the cornea under stress. Combined with waveform parameters of the ocular response analyzer, more subtle changes of corneal biomechanical properties can be found.(Chin J Ophthalmol, 2017, 53:23-32).
Tianjin Medical University, Clinical College of Ophthalmology, Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin 300020, China.
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Dou
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Zhang
D000704:Analysis of Variance; D001251:Astigmatism / Q000601:surgery*; D001696:Biomechanical Phenomena; D003315:Cornea / Q000503:physiopathology*; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D008297:Male; D009216:Myopia / Q000601:surgery*; D011184:Postoperative Period; D013997:Time Factors
Biomechanics; Cornea; Keratomileusis, laser in situ; Laser, femtosecond