CNGA3 encodes the pore-forming alpha subunit of the cone cyclic nucleotide-gated (CNG) channel, essential for phototransduction in bright light conditions 1. In darkness, high cGMP levels keep the channel open, allowing inward current from Na+ and Ca2+ ions that depolarizes cone photoreceptor membranes and enables neurotransmitter release 1. Upon photon absorption, cGMP levels decline, closing the channel and hyperpolarizing the membrane, thereby signaling light detection 1. CNGA3 also functions in gustatory CNG channels where it may sense oral pH and modulate taste cell excitability 1. Pathogenic CNGA3 variants cause achromatopsia, an autosomal recessive cone dysfunction syndrome affecting 1 in 30,000 individuals 2. Up to 90% of achromatopsia patients carry CNGA3 or CNGB3 mutations 1. Disease manifests at birth or early infancy with poor visual acuity, nystagmus, photophobia, and complete color vision loss due to cone photoreceptor dysfunction and slow progressive degeneration 1. No FDA-approved therapy currently exists 2. However, preclinical studies demonstrate that intravitreal adeno-associated virus (AAV) gene therapy delivering CNGA3 achieves cone-specific protein expression and rescues photopic cone responses in animal models 3. Multiple phase I/II clinical trials for CNGA3-linked achromatopsia are registered, offering potential therapeutic hope for affected patients 2.