PAX6 and aniridia: In many of them, mutations in a single gene can explain most cases, e.g., PAX6 and aniridia (Landsend et al. 2021)⁠, ABCA4 and Stargardt disease (Cremers et al. 2020)⁠, or NF1 and Neurofibromatosis type 1 (Koster et al. 2021)⁠.