Comparison of Early Visual Quality in Patients using Different Optical Zones Based on Dark Pupil Diameters in Small Incision Lenticule Extraction (SMILE)

AIM: The early visual qualities of patients were evaluated after small incision lenticule extraction (SMILE) using different optical zones based on dark pupil diameters. METHODS: A case-control study was conducted to include 49 myopic patients (96 eyes) who underwent SMILE surgery. Patients were divided into three groups according to the difference between the diameter of the optical zone and the diameter of the dark pupil: Group A (1 mm, N=30). In all groups, the dark pupil diameter was measured preoperatively. Subjective visual quality, uncorrected vision acuity (UCVA), spherical equivalent (SE), modulation transfer function cut-off frequency (MTF cutoff ), objective scattering index (OSI), simulated contrast visual acuity (VA100%, VA20%, VA9%), total corneal higher-order aberration (tot-HOA), corneal spherical aberration (totZ40) and corneal coma (tot-coma) were measured preoperatively and 3 months postoperatively. P< 0.05 was considered statistically significant. RESULTS: There were no statistically significant differences in age, sex, UCVA, SE, corneal higher-order aberration, OQAS or subjective visual quality among the three groups before surgery (P>0.05). At 3 months postoperatively, there was no significant difference in UCVA, SE, MTF cutoff , OSI, VA100%, VA20%, or VA9% among the three groups (P>0.05). However, the tot-HOA, totZ40 and tot-coma indexes and the changes in corneal higher-order aberrations (Dtot-HOA, DtotZ40, Dtot-coma) at 3 months postoperatively were as follows: Group A > Group B > Group C (P<0.05). At 3 months postoperatively, the difference in subjective visual quality between the three groups was statistically significant (P<0.05). The difference in the amount of change in subjective visual quality between Groups A and C was statistically significant (P<0.05). CONCLUSION: Although the difference between the diameter of the optical zone and the diameter of the dark pupil does not affect the VA or the same diopter of patients after SMILE myopia correction, the optical zone diameter should be greater than the dark pupil diameter as far as possible in the design of SMILE surgery, in order to improve the objective visual quality and subjective satisfaction of patients after surgery.