ARR3 encodes cone arrestin, a retina-specific signal transduction protein expressed in red-, green-, and blue-sensitive cone photoreceptors 1. The protein binds to photoactivated-phosphorylated cone opsins to inactivate phosphorylated visual receptors and terminate cone phototransduction signaling 2. ARR3 also functions as an adaptor protein mediating G protein-coupled receptor internalization through clathrin-coated pits 3. ARR3 pathogenic variants cause Myopia-26 (MYP26), transmitted as X-linked female-limited early-onset high myopia affecting individuals under age 7 with severe refractive error (ranging from −5.00 to −28.75 diopters) 4. ARR3 is the most frequently implicated gene for Mendelian early-onset high myopia, with 29 pathogenic variants identified in 78 affected individuals 4. Both truncation and highly scored missense variants are pathogenic 5. Affected individuals exhibit cone dysfunction, with reduced light-adapted electroretinogram amplitudes (~35–55% reduction) and progressive color vision defects 62. Myopic fundus changes and peripheral retinal degeneration occur in subsets of patients, progressing slowly to pathologic myopia 4. Females heterozygous for ARR3 mutations show symptoms, while a hemizygous male case suggests a more complex inheritance pattern than initially recognized 7. No disease-modifying therapies have been established for ARR3-associated myopia.