Background/aim This study aimed to provide an objective assessment of the effects on the aqueous outflow rate of various geometries of the scleral flap and sclerostomy created in trabeculectomy.

Method Computer-based models and simulations of this surgical procedure were used to investigate the relative effects of various shapes and dimensions of scleral flap and sclerostomy on the aqueous outflow.

Result In these computer simulations, increasing scleral flap size was found to be associated with an increase of 48.55% in aqueous egress. In addition, a square scleral flap increased the aqueous drainage by 36.26% compared with a triangular flap of equivalent flap area. Surprisingly, our simulation results showed that a smaller semicircular sclerostomy improved aqueous drainage by up to 33.00%, while a semicircular sclerostomy, compared with a circular sclerostomy, led to a further 6.16% increase in aqueous outflow. Decreasing flap thickness beyond half-thickness caused an additional increase in aqueous outflow. However, clinically the flap should not be thinner than half the thickness of the sclera as this may result in hypotony.

Conclusion These simulations indicate that the optimal flow rate through operation site will be achieved in trabeculectomy using a square scleral flap with a large flap-to-sclerostomy ratio.