Based on evidence that melanopsin dysfunction is related to sleep disorders in late glaucoma patients26 and reports that melanopsin gene (OPN4) variants modulate the pupil response and sleep behaviour55, 56, 57, 58, a secondary aim was to investigate if the established OPN4 variants could affect the PIPR or sleep, independent of the different stages of glaucoma. The gene discussed is OPN4; the disease is sleep disorder.