Long-term outcomes of prediction error after combined phacoemulsification and trabeculectomy in glaucoma patients

BACKGROUND: To investigate long-term outcomes of prediction error after phacotrabeculectomy and to determine risk factors that may cause unstable prediction error after phacotrabeculectomy in glaucoma patients. METHODS: A total 120 eyes of 120 patients who had underwent uncomplicated phacotrabeculectomy (combined group) or phacoemulsification (phaco-only group) were included. Best-corrected visual acuity (BCVA), intraocular pressure (IOP) were measured before and after surgery, and anterior segment parameters including anterior chamber depth (ACD), lens vault (LV), and anterior vault (AV) measured using anterior-segment optical coherence tomography were compared between the two groups. The mean absolute error (MAE) at 3, 6, 12, and 24 months postoperatively were compared. Risk factors associated with unstable prediction error (MAE ≥ 0.5) were investigated in the combined group. RESULTS: In both groups, BCVA was improved and IOP was decreased significantly. MAE at 3, 6, 12, 24 months postoperatively were not significantly different between two groups. The risk factors for unstable prediction error after 12 months of phacotrabeculectomy were old age and LV. Whereas, the only factor predicting unstable prediction error after 24 months of phacotrabeculectomy was LV. The cut-off value of LV for predicting unstable refractive error analyzed by the ROC curve was 0.855 mm. CONCLUSIONS: Phacotrabeculectomy may be an effective treatment with stable long-term outcomes of prediction error similar to phacoemulsification in patients with glaucoma. However, elderly patients or patients with large LV may be predisposed to unstable prediction error after phacotrabeculectomy.