Analysis of anterior chamber morphological changes after small incision lenticule extraction

Abstract

Objective To investigate the changes of anterior chamber profiles after small incision lenticule extraction(SMILE) and analyze the possible influencing factors. Methods A case observation study was designed.Thirty-one patients(59 eyes) with myopia and myopic astigmatism who underwent SMILE surgery at the Refractive Surgery Center of Tianjin Eye Hospital from April to December 2015 were enrolled and examined preoperatively and at 1 month, 3 and 6 months postoperatively.The anterior chamber profiles, including anterior chamber depth (ACD), anterior chamber volume (ACV) and anterior chamber angle (ACA) were measured using the Pentacam.The correlations between parameters were analyzed and the differences of the parameters at different time points were compared.This study followed the Declaration of Helsinki.This study protocol was approved by Ethic Committee of Tianjin Eye Hospital (No.TJYYLL-2015-20). Written informed consent was obtained from each subject before the operation. Results Compared with pre-operation, the central corneal thickness (CCT) was significantly decreased at 1 month, 3 and 6 months postoperatively (all at P 0.05). The posterior corneal elevation (PCE) at different time points before and after surgery was significantly different (F=19.249, P<0.001), compared with the preoperation, the PCE at 1 month, 3 and 6 months postoperatively moved slightly backward (all at P<0.05). The preoperative ACD was (3.33±0.25)mm, the preoperative ACV was (217.46±31.55)mm3, and the ACD was (3.31±0.25), (3.30±0.25) and (3.30±0.25)mm, the ACV was (214.71±33.09), (211.14±33.65) and (210.08±32.19)mm3, respectively at 1 month, 3 and 6 months postoperatively, with significant differences at different time points before and after surgery (F=12.477, 12.205; both at P<0.001), compared with the preoperation, the ACD at 1 month, 3 and 6 months postoperatively and ACV at 3 months and 6 months postoperatively were obviously decreased, with a significant difference between them (all at P<0.05). There was a significant positive correlation between ACD and ACV at different time points before and after surgery (r=0.870, 0.893, 0.886, 0.884; all at P<0.001). The preoperative ACD was negatively correlated with CCT (r=-0.286, P<0.05). Conclusions The ACD is decreased postoperatively, it is basically stable at (3.30±0.25)mm, which satisfies the requirements of the ACD required for implantable collamer lens.And the stable state of ACD is also important for keratoconus detection. Key words: Small incision lenticule extraction; Anterior chamber depth; Anterior chamber volume; Anterior chamber angle