ARR3 (arrestin 3) encodes cone arrestin, a retinal protein that plays a critical role in cone phototransduction by inactivating phosphorylated opsins and terminating cone cell signals 1. The protein is specifically expressed in cone photoreceptors where it binds to photoactivated-phosphorylated red/green opsins to regulate visual signal transduction 2. Pathogenic variants in ARR3 are the most frequently implicated genetic cause of Mendelian early-onset high myopia (eoHM), following an X-linked female-limited inheritance pattern 3. The disease mechanism involves cone dysfunction, with affected patients showing mild-to-moderately reduced cone responses on electroretinography and progressive color vision defects 34. Clinical significance includes severe myopia ranging from -5.00 to -28.75 diopters, with most patients developing mild myopic fundus changes that can progress to pathologic myopia 3. The cone dysfunction observed in ARR3-associated myopia is specifically linked to the genetic mutation rather than being a consequence of eye elongation 4. Various pathogenic variants have been identified, including truncation mutations, missense variants, and splicing variants, all leading to similar phenotypes of early-onset high myopia with cone dysfunction 56.