AIM: To analyze the factors influencing total corneal surgically induced astigmatism(SIA)following implantable collamer lens(ICL)implantation.METHODS:This prospective study enrolled 162 patients(162 eyes)who underwent ICL implantation at our hospital between July 2023 and January 2024. Based on preoperative assessment of anticipated postoperative residual astigmatism, different incisions were selected. Superior incision was selected for patients with expected residual astigmatism with the rule in 75 eyes, and temporal incision was selected for patients with expected residual astigmatism againist the rule in 87 eyes. Parameters including total corneal refractive power, incision length, internal ostium-to-visual axis distance, central corneal thickness, preoperative total corneal astigmatism, and corneal diameter were measured using the Pentacam anterior segment analyzer before and at 3 mo after surgery. Postoperative total corneal SIA was calculated based on the changes in total corneal refractive power. Multiple linear regression analysis was performed to assess the influence of the above parameters on postoperative total corneal SIA.RESULTS:A total of 162 cases(162 eyes)that implanted with ICL were included in the analysis, and 8 cases were lost to follow-up, with a loss rate of 4.9%. Eventually 154 cases(154 eyes)completed the research. The superior incision group comprised 72 cases(72 eyes), including 17 males and 55 females, with a mean age of 25.96±6.17 years, while the temporal incision group comprised 82 cases(82 eyes), including 20 males and 62 females, with a mean age of 27.79±6.47 years. No significant difference in postoperative total corneal SIA was observed between the two groups [0.31(0.21, 0.49)D vs. 0.27(0.13, 0.485)D, P=0.159]. Multiple linear regression analysis revealed that internal ostium-to-visual axis distance and preoperative total corneal astigmatism significantly influenced postoperative total corneal SIA in the superior incision group(P=0.001). The regression equation was: postoperative total corneal SIA=0.71-0.381×internal ostium-to-visual axis distance+0.16×preoperative total corneal astigmatism. No significant influencing factors for postoperative total corneal SIA were identified in the temporal incision group.CONCLUSION: During ICL implantation, the magnitude of total corneal SIA is comparable between superior and temporal incisions. For patients receiving a superior incision, the internal ostium-to-visual axis distance and preoperative total corneal astigmatism value can be used to quantitatively predict postoperative total corneal SIA to a certain extent, thereby aiding in the optimization of postoperative visual quality.

AIM: To quantitatively evaluate the vectorial effect of different incision locations on surgically induced astigmatism(SIA)following implantable collamer lens(ICL)implantation and to clarify the relative contributions of the anterior and posterior corneal surfaces to total corneal SIA.METHODS: A prospective study was conducted on who underwent ICL/toric ICL implantation between July 1, 2023 and January 1, 2024. Patients were divided into superior incision group and temporal incision group according to the expected postoperative residual astigmatism. Pentacam measurements were performed preoperatively and at 3 mo postoperatively to obtain total corneal refractive power and anterior and posterior corneal curvature radii. Anterior and posterior corneal surface powers and total corneal astigmatism were calculated. Thibos vector analysis was applied to decompose corneal astigmatism into orthogonal components J0 and J45, and the changes in J0(ΔJ0)were calculated for each surface. Multiple linear regression analysis was performed to explore the associations of anterior surface ΔJ0, posterior surface ΔJ0, and incision location with total corneal ΔJ0.RESULTS: This study included 162 patients(162 eyes), with 75 patients 75 eyes in the superior incision group and 87 patients 87 eyes in the temporal incision group. Totally 154 patients(154 eyes)completed follow-up: 72 patients(72 eyes)in the superior incision group(17 males and 55 females, aged 25.96±6.17 y)and 82 patients(82 eyes)in the temporal incision group(20 males and 62 females, aged 27.79±6.47 y). In the superior incision group, the total cornea and anterior surface J0 shifted toward positive values(against-the-rule), with ΔJ0 of 0.146±0.108 D and 0.199±0.117 D, respectively, while the posterior surface J0 shifted toward negative values(with-the-rule), with ΔJ0 of -0.050±0.022 D. The temporal incision group showed the opposite trend. Multiple regression analysis showed an excellent model fit(adjusted R2=0.943), with anterior surface ΔJ0 as the main influencing factor(B=0.968, β=1.137, P<0.001)and posterior surface ΔJ0 also contributing independently and significantly(B=1.018, β=0.297, P<0.001). Incision location and its interaction terms with anterior and posterior surface ΔJ0 were not statistically significant(all P>0.05).CONCLUSION: Based on 3 mo postoperative followup, superior incisions induce a predominant withtherule SIA vector, while temporal incisions induce a predominant againsttherule SIA vector. Anterior surface ΔJ0 is the primary contributor to total corneal ΔJ0, and posterior surface ΔJ0 also demonstrates a statistically significant association.