All the above genes proved to be potentially involved in TR determination: defects in VPS54 could lead to RPE degeneration, thus leading to color vision impairment; alterations in IQGAP1 can cause cone type imbalances, with a diminished number and functionality of S cones; defects in NMB may alter RPE’s ability to regulate fluid homeostasis, resulting in subretinal fluid accumulation and retinal function impairment; alterations in MC5R could affect lacrimal gland function leading to dry eye onset and progressive visual impairment. Here, MC5R is linked to Keratoconjunctivitis sicca.