NM_000330.4(RS1):c.581T>A (p.Ile194Asn) is a missense variant encoding the substitution of isoleucine with asparagine at position 194. This variant is absent from hemizygous individuals in gnomAD v4.1.0 (PM2_Supporting). This variant has been reported in at least 2 apparently unrelated probands meeting the PS4 requirement of a male diagnosed with X-linked retinoschisis (PMID: 29739629, PMID: 19324861, PS4_Supporting). At least one proband harboring this variant exhibits a phenotype including appearance of schisis and reduced visual acuity before age 13 years, and showing retinal detachment, which together are highly specific for X-linked retinoschisis (PMID: 32300273, PP4_Moderate). The variant has been reported to segregate with affected status through 3 meioses within 1 family (PP1_Strong; PMID: 24505212). The computational predictor REVEL gives a score of 0.956, which is above the ClinGen X-linked IRD VCEP threshold of >0.932 and predicts a damaging effect on RS1 function (PP3_Strong). The computational splicing predictor SpliceAI gives a delta score of 0.00 for all predictive splice changes, which is below the ClinGen X-linked IRD VCEP threshold of >0.2 and does not predict that the variant disrupts RS1 splicing. In summary, this variant is classified as pathogenic for X-linked retinoschisis based on the ClinGen X-linked Inherited Retinal Disease Expert Panel Specifications to the ACMG/AMP Variant Interpretation Guidelines for RS1 Version 1.0.0: PM2_Supporting, PP3_Strong, PP1_Strong, PP4_Moderate, and PS4_Supporting.