Light-responsive rhodamine-derivative embedded 3D-printed contact lenses with enhanced optical and mechanical properties for next-generation ophthalmic applications

Color vision deficiency (CVD), particularly red-green impairment, affects a large global population and is inadequately addressed by current corrective devices, which suffer from uniform tinting, poor spectral selectivity, and limited wearer comfort. Here, we present the fabrication of rhodamine B hydrazide (RhB-HZ)-embedded hydrogel contact lenses (RhB-HZ@CL) using digital light processing (DLP)-based 3D printing, offering a cost-effective and multifunctional alternative that has not been previously explored in contact lens fabrication. RhB-HZ is a derivative of Rhodamine B, 10–50 times cheaper than specialized chromophores, and undergoes a UV-triggered spirolactam ring-opening reaction, generating a stable pink coloration with a strong absorption maximum at 562 nm. This enables the selective blocking of 80–90% of the problematic 500–600 nm spectral region while preserving overall transparency under normal lighting conditions. Structural evaluations confirmed suitable water content and wettability, with the contact angle reduced from 81.64° (pristine) to 64.36–67.59° (RhB-HZ-loaded), ensuring improved tear-film stability. Thermal stability was maintained, with degradation onset occurring near 350 °C, validating the robustness of the processing. Mechanical testing revealed that at 0.01 wt% RhB-HZ, tear propagation strength increased to 5.95 ± 1.16 N with minimal compromise to tear initiation resistance (3.34 ± 0.83 N). Higher dye concentrations (0.03–0.05 wt%) led to reduced initiation forces (2.36–3.32 N) due to dye aggregation. Collectively, RhB-HZ@CL lenses integrate spectral selectivity, photostability, and biocompatibility with scalable, low-cost manufacturing, establishing them as a promising next-generation platform for discreet and effective CVD correction.