Large genome-wide association studies associate common intronic single-nucleotide polymorphisms (SNPs) in COL4A1-COL4A2 with SVD phenotypes, including lacunar stroke,10,11 subcortical hemorrhages,10,11 and diffuse WMLs.10,12 As these SNPs are noncoding, their effects on phenotype likely reflect either excessive or insufficient levels of vascular collagen-IV. Here, COL4A1 is linked to snowflake vitreoretinal degeneration.