Optical Zone Customisation In Smile For Large Scotopic Pupils: A Three-Group Comparative Study Of Quality Of Vision And Dysphotopsia At Three Months

To evaluate postoperative quality of vision (QoV) and dysphotopsia following SMILE in patients with large scotopic pupils, and to determine whether optical zone (OZ) enlargement mitigates potential pupil-related visual disturbances. Outcomes were compared across three cohorts: large pupils treated with enlarged OZ, large pupils treated with standard OZ, and normal pupils treated with standard OZ.

Retrospective comparative cohort study conducted at Cathedral Eye Hospital, Belfast, United Kingdom, between December 2024 and November 2025. Patients undergoing bilateral SMILE using the VisuMax (Carl Zeiss Meditec) platform were included.

Preoperative scotopic pupil diameter was measured using the Schwind Peramis. Sixty age-matched patients were analysed (20 per group): (1) large pupils treated with enlarged OZ of 6.9 mm and a 7.9 mm cap, (2) large pupils treated with standard OZ of 6.5 mm and a 7.5 mm cap, and (3) normal pupils treated with standard OZ of 6.5 mm and a 7.5 mm cap. Three-month outcomes included visual acuity and a modified McAlinden Quality of Vision questionnaire with global daytime and nighttime scores (0–10). Between-group comparisons used Kruskal–Wallis testing with Dunn’s post-hoc analysis. Within-group changes were assessed using two-tailed Wilcoxon signed-rank tests. Categorical outcomes were analysed using chi-square tests.

Daytime QoV differed significantly between groups (Kruskal–Wallis p=0.011), with higher scores in large pupils treated with enlarged OZ compared with large pupils treated with standard OZ (Dunn-adjusted p=0.015). In contrast, nighttime QoV did not differ significantly between groups (p=0.335). Significant pre to postoperative improvement in both daytime and nighttime QoV were observed in the enlarged-OZ and normal pupil cohort (p<0.05), no significant improvement was detected in large pupils treated with standard OZ. Post-op Haloes were more frequently reported in large pupils treated with standard OZ (χ² p=0.044), however symptom severity did not differ significantly. Post-op glare and starburst were similar across groups.

In eyes with large pupils where corneal thickness precluded OZ enlargement, a standard treatment zone was applied. In this subgroup, postoperative QoV was not inferior to baseline. However, when compared directly with large-pupil eyes treated with an enlarged OZ, the standard-zone group demonstrated lower postoperative daytime QoV and a higher prevalence of haloes.

Enlargement of OZ and cap parameters in large scotopic pupils was associated with improved daytime visual quality and dysphotopsia rates comparable to normal-pupil eyes. These findings support a tailored OZ enlargement in large-pupil eyes, where corneal thickness allows, to optimise visual quality without compromising refractive safety.