Development, Mechanical Performance, and Ex Vivo Porcine Eye Biomechanical Validation of a 3D-Printed Schepens Scleral Depressor

Purpose : To develop a low-cost, 3D-printed Schepens scleral depressor and evaluate its mechanical performance, safety, and ocular biomechanical effects. Methods: A Schepens-style depressor was developed and printed in PLA using a 3D-printer. Examiners performed two different tests: (1) the maximum simulated scleral depression force, using both the 3D-printed and a conventional steel depressor, and (2) a breakage test performed only on the 3D-printed device to determine its mechanical failure threshold. Peak forces were applied to porcine belly and recorded by a precision balance with a slow-motion video analysis. A third test - conduced exclusively with the 3D-printed depressor - was performed using one ex vivo porcine eye model to correlate applied force with induced intraocular pressure (IOP) elevation. Pressure–volume behavior was modeled using the Friedenwald rigidity coefficient. Results: One unit of the depressor prototype consumed 3.06g of PLA with an estimated cost and print time of U$0.06 and 22min. Simulated indentation produced forces of 21.21 ± 6.23N (3D-printed depressor) and 25.02 ± 4.64N (steel depressor), with no significant difference between devices. The 3D-printed instrument breakage point was 63.27 ± 10.72N, with a 2.98 Factor of Safety (FS) and 3.39 Reliability Index (b). In the porcine model, scleral depression produced 15.63 ± 8.13mmHg IOP elevation, requiring 0.191 ± 0.09N (FS = 331.2 and b = 5.88). Conclusion: 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.