In SCA‐ATXN1 patients, time since onset showed a positive correlation with GCIP (B = 0.012; standard error [SE] = 0.005; P = 0.014), but not pRNFL (B = 0.480; SE = 0.424; P = 0.260). This evidence concerns the gene ATXN1 and autosomal dominant cerebellar ataxia.