A curved-mold assisted slow evaporation approach for uniform dye integration in commercial hydrogel lenses

Functionalities such as drug delivery, sensing, and selective wavelength filtering are often added to contact lenses through the incorporation of various additives. For color blindness correction, selective wavelength filtering dyes are often investigated for improving color differentiation. Here, in this work, we explore a mold-assisted slow evaporation technique to incorporate water-soluble dyes into commercial hydrogel contact lenses. The technique allows successful dye integration and uniform staining of curved contact lenses without any visible artifacts or uneven regions. Commercial alcohol-based dyes as well as Atto 425, Atto 465, Atto 488, Atto 495, and Atto 565 were prepared using this technique. The lenses showed filtering capabilities for problematic wavelengths while retaining 80% transparency in the rest of the regions. The lenses showed excellent UV stability. The patient trial was performed using the Ishihara plate reading test, which indicated the lens capable of color differentiation varies from patient to patient. The reproducibility test done by measuring RGB values (0-255) showed a minimal deviation within value of 2.