OPN1MW3 encodes a medium-wave sensitive opsin, a visual pigment consisting of apoprotein covalently linked to cis-retinal. It functions as a G protein-coupled photoreceptor in cone cells, mediating light absorption and phototransduction through adenylate cyclase-inhibiting signaling. Based on limited published evidence, OPN1MW3 expression is downregulated in zebrafish larvae exposed to the endocrine disruptor triclocarban, correlating with impaired red and green light sensitivity 1. Additionally, OPN1MW3 expression declines in Parkinson's disease patients, suggesting color vision analysis may serve as a disease progression biomarker 2. Mutations cause blue cone monochromacy, deutan colorblindness, and cone dystrophy 5.