Development and biomechanical validation of a 3D-printed Schepens scleral depressor.

Abstract

This study aimed to develop a low-cost 3D-printed scleral depressor and evaluate its mechanical performance, safety margins, and ocular biomechanical effects. A Schepens-style depressor was developed and printed in PLA. Examiners performed two different tests: (1) the maximum simulated scleral depression force, using both the 3D-printed and conventional steel depressors, and (2) a breakage test performed only on the 3D-printed device, determining its mechanical failure threshold for probabilistic safety analysis. Peak forces were applied to the porcine belly and recorded by a precision balance with slow-motion video analysis. A third test, which was conducted exclusively with the 3D-printed depressor, was performed using one ex vivo porcine eye model to correlate the applied force with the induced intraocular pressure (IOP) elevation. The pressure-volume behavior was modeled via the Friedenwald rigidity coefficient. One unit of the depressor prototype consumed 3.06 g of PLA, with an estimated cost and print time of U$ 0.06 and 22 min, respectively. The simulated indentations produced forces of 21.21 ± 6.23 N (3D-printed depressor) and 25.02 ± 4.64 N (steel depressor), with no significant difference between devices. The 3D-printed instrument breakage point was 63.27 ± 10.72 N, with a 2.98 factor of safety (FS) and 3.39 reliability index (β). In the porcine model, scleral depression produced a 15.63 ± 8.13 mmHg increase in IOP, requiring 0.191 ± 0.09 N (FS = 331.2 and β = 5.88). The 3D-printed depressor demonstrates effective mechanical robustness, wide safety margins, and functional equivalence to steel instruments, supporting the use of customizable, low-cost 3D-printed depressors in training and clinical settings.