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.