Dear Editor,

We thank Drs Mahrood et al. for bringing to our attention their latest findings in relation to the seminal report implicating pathogenicity of RIMS1. Their conclusion that RIMS1 lacks an evidentiary base as a monogenic cause of retinal dystrophy, is reassuring for our patient, who in most respects displays a profile of incomplete congenital stationary night blindness [1]. We note however the presence of unusually depressed scotopic responses in our case. Whilst this may reflect heterogeneity within the CACNA1F-related disease spectrum [2], the possibility of allelic modifiers is also acknowledged. Raising the question as to whether the identified variance in RIMS1 is phenotypically complicit or simply an innocent bystander; and emphasising the importance of interrogation of potential modifying factors across the inherited retinal dystrophies.