Comparative analysis of preoperative and postoperative changes in photopic and mesopic angle kappa and angle alpha in cataract surgery

To evaluate changes in angle kappa (κ) and angle alpha (α) under photopic and mesopic illumination before and after cataract surgery, and to analyze their correlations with ocular biometric parameters. This prospective study included 93 eyes of 93 patients undergoing standard phacoemulsification with intraocular lens implantation in the First Affiliated Hospital of Nanchang University between January 2024 and December 2024. Preoperative measurements included axial length, white‑to‑white corneal diameter, anterior chamber depth, lens thickness, and central corneal thickness. Angles κ and α were recorded using the OPD‑Scan III under photopic and mesopic conditions before and 1 month after surgery. Postoperatively, mean photopic angle κ decreased significantly (P < 0.001), whereas mesopic angle κ showed no significant change. Both photopic and mesopic angle α remained stable (P > 0.05). Preoperative photopic angle κ correlated negatively with axial length (r = − 0.31, P = 0.002) and positively with lens thickness (r = 0.28, P = 0.006). Changes in angle κ were associated with reductions in lens thickness and increases in anterior chamber depth; angle α changes were not significantly related to biometric parameters. Phacoemulsification induces a significant reduction in photopic angle κ but not angle α, with changes linked to specific biometric alterations. These findings may help refine intraocular lens centration strategies and improve postoperative visual outcomes.