Background/aims To investigate longitudinal changes in anterior chamber depth (ACD) and axial length (AXL) over 5 years after trabeculectomy surgery in Asian patients with primary glaucoma, and to identify factors associated with these changes.

Methods In this prospective cohort study, phakic subjects with primary glaucoma who underwent trabeculectomy had ACD and AXL measured over 5 years. The effect of intraocular pressure (IOP) on ACD and AXL was determined. Subjects were divided into two groups (high or low fluctuation of ACD/AXL) and factors were compared to determine if there were factors associated with greater fluctuation.

Results 122 subjects were analysed. The majority of subjects were male (75.4%) and Chinese (77%). ACD and AXL were shallower/shorter compared with baseline at all postoperative visits, with a mean decrease of 0.11 mm (95% CI 0.07 to 0.15 mm, p<0.01) and 0.16 mm (95%CI 0.11 to 0.20 mm, p<0.01), respectively. Patients with primary open angle glaucoma (POAG) had higher odds of fluctuations in longitudinal measurements of ACD (OR=8.74, p<0.01) and AXL (OR=5.60, p<0.01) compared with patients with primary angle closure glaucoma. For every 1 mm Hg decrease in IOP, ACD and AXL decreased by 0.02 mm (p<0.01) and 0.01 mm (p=0.03), respectively, for POAG patients with emmetropia or mild myopia.

Conclusions Trabeculectomy resulted in a decrease in both ACD and AXL, and these changes were persistent over a period of 5 years.