Abstract: Objective The objective of this study is to observe the effect of the relationship between the diameter of the optical zone and the diameter of the dark pupil on the visual quality of patients with different degrees of myopia after small incision lenticule extraction(SMILE). Methods A retrospective analysis was performed on 96 eyes from 49 myopic and astigmatic patients aged 18 to 35 years(average age of 25.76±5.75 years)who underwent SMILE surgery in our ophthalmology center in July 2021. Based on the difference between the diameter of the optical zone and the diameter of the dark pupil, they were divided into three groups: group A, <0 mm(30 eyes); group B, 0-1 mm(36 eyes); and group C, > 1 mm(30 eyes). Each group was then divided into mild to moderate myopic groups(<-6.00D)and high myopic groups(≥-6.00D)according to spherical equivalent refraction(SE). The patients' uncorrected visual acuity(UCVA), SE, high-order corneal aberration, modulation transfer function(MTF)cutoff, object scatter index(OSI), and responses to the subjective visual quality questionnaire were recorded before and 3 months after surgery. Parameter variation was represented by Δ, which was calculated by subtracting the preoperative parameter value from that obtained 3 months postoperatively. Results Preoperative baseline optical zone diameter, dark pupil diameter, and their differences were statistically significant(all P<0.01), whereas age, sex, UCVA, SE, corneal higher-order aberration, MTF cutoff, OSI, and subjective visual quality were not statistically significant(all P>0.05). There were no significant differences in UCVA and SE between the three groups at 3 months after operation(all P>0.05), whereas significant differences were noted in the corneal coma, spherical aberration, and total higher-order aberration(all P<0.05). Pairwise comparisons showed that the values in group A was higher than those in groups B and C, and the differences were statistically significant(all P<0.05). Postoperative corneal aberration in all three groups were higher than that before surgery(all P<0.05). A pairwise comparison of Δspherical aberration in patients with high myopia showed that the values of group C were lower than those of groups A and B, and the differences were statistically significant(P=0.045 and 0.047, respectively). A pairwise comparison of Δspherical aberration and Δtotal high-order aberration in patients with mild to moderate myopia showed that the values of group A were higher than those of group B, with statistically significant differences(P=0.003 and 0.006, respectively), and no statistically significant differences were found between groups B and C(P=0.464 and 0.962, respectively). The patients' MTF cutoff values at 3 months after surgery were restored to the preoperative level (P>0.05). When the difference between the diameter of the optical zone and the diameter of the dark pupil was less than 0 mm, the OSI at 3 months after surgery was higher than that before surgery(P=0.007). The subjective visual quality scores of groups B and C after surgery(7.53±3.81 and 7.73±3.88, respectively)were lower than those before surgery(9.75±4.05 and 11.00±6.35, respectively)(P=0.002 and 0.003, respectively). Conclusion When the optical zone diameter was larger than the dark pupil diameter, the subjective satisfaction of myopia patients significantly improved, and the increase in comas, spherical aberration, and total high-order aberration decreased. On this basis, patients with high myopia require a larger optical zone diameter to reduce the increase in postoperative corneal spherical aberration.

Key words: Small incision lenticule extraction(SMILE), Optical zone diameter, Pupil diameter of darkroom, Myopia, Corneal high-order aberration, Visual quality