[Effect of optical zone diameter on corneal biomechanical properties after small incision lenticule extraction].
Objective:To investigate the effect of optical zone diameter on corneal biomechanical properties after small incision lenticule extraction (SMILE).Methods:In this prospective case-control study, 62 eyes of 42 patients with myopia and myopic astigmatism that had undergone SMILE procedure were divided into 2 groups according to the optical zone (OZ) diameter: group A, 31 eyes of 19 patients, OZ=6.5 mm; group B, 31eyes of 23 patients, OZ=6.0 mm. These patients were examined for corneal hysteresis (CH) and corneal resistance factor (CRF) with the Ocular Response Analyzer (ORA) preoperatively and at 1 week, 1 month and 3 months postoperatively; at the same time, the central corneal thickness-corrected indices of DifCH and DifCRF were calculated. Pearson correlation was applied to analyze the correlation between CH and CRF and central corneal thickness. Independent-samples t test was utilized to compare CH and CRF between the two groups. Repeated ANOVA was used to compare the difference of corneal biomechanical properties at different follow-up timepoints.Results:The preoperative mean CRF and CH values were (10.13±1.19) mmHg and (9.65±1.12) mmHg in group A and (10.34±0.89) mmHg and (10.04± 1.05) mmHg in group B, respectively, and no significant differences were found in CRF and CH between the two groups (CRF:t=-0.807,P=0.423. CH:t=-1.405,P=0.165). The mean CRF values in group A at postoperative 1 week and 3 months were (6.62 ± 1.09) mmHg and (6.83 ± 1.07) mmHg, respectively, which were significantly lower than the relevant mean CRF values in group B (t=-2.703,P=0.009.t=-3.733,P=0.001). Meanwhile, the mean CH values at 1 week, 1 month and 3 months postoperatively in group A were (7.31±1.06) mmHg, (7.37±0.96) mmHg and (7.82±0.97) mmHg, respectively, which were significantly lower than those in group B (t=-2.415,P=0.019.t=-2.113,P=0.039.t=-2.67,P=0.01). Moreover, the DifCRF and DifCH values in group A were significantly lower than those in group B at 3 months postoperatively (t=-3.409,P=0.001.t=-2.064,P=0.044). The CRF and CH values in both groups showed a significant reduction at 1 week, 1 month and 3 months postoperatively (P<0.05).Conclusions:The size of optical zone has some effects on corneal biomechanical properties after SMILE. The smaller optical zone diameter has a relatively smaller effect.(Chin J Ophthalmol, 2017, 53:182-187).
Tianjin Medical University, Clinical College of Ophthalmology, Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin 300020, China.
P H
PH
Wei
Y
Y
Wang
H
H
Li
R
R
Dou
L Y
LY
Li
W
W
Zhao
J M
JM
Zhang
D000328:Adult; D001251:Astigmatism / Q000503:physiopathology / Q000601:surgery*; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D003315:Cornea; D019781:Corneal Topography; D004548:Elasticity / Q000502:physiology*; D005260:Female; D005654:Fundus Oculi; D006801:Humans; D008297:Male; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D011184:Postoperative Period; D011446:Prospective Studies
Biomechanics; Cornea; Corneal curgery, laser; Corneal pachymetry; Corneal stroma; Laser, femtosecond