In a retrospective study, 7% of a well-characterised CVI cohort had at least one clinically significant chromosomal abnormality.12 Building on this finding of a high genomic diagnostic yield, trio exome sequencing was carried out for 25 cases of idiopathic CVI, which identified a definite or potential genetic aetiology in 16 individuals.13 Variants were found in four genes previously associated with CVI (AHDC1, NGLY1, NR2F1 and PGAP1) and 19 further candidate genes. Here, AHDC1 is linked to Cerebral visual impairment.