Investigating ethnicity-related variability in the human L-cone spectral sensitivity function.

The human cone photoreceptor spectral sensitivities can differ between individuals. Large changes give rise to color vision deficiencies, but even among color-normals there is systematic individual variation. Characterizing the sources of this variation is important for understanding how well widely-used average spectral sensitivity functions represent diffferent observers. One contributor to individual differences in L-cone spectral sensitivity is the amino acid at position 180 of OPN1LW, which encodes the L-cone photopigment. Here, we examine group differences in the reported frequency of the L(S180) and L(A180) alleles using a combination of published reports and the genome sequencing database, gnomAD. We found the estimated allele frequencies differ across reported ethnicity categories. Thus, L-cone spectral sensitivity functions derived from historically available samples may not capture all population-level variation equally, particularly when applied to groups that were under-represented in the underlying datasets. We discuss how population-level variation of this kind relates to the interpretation and use of standard observer functions, and we outline recent promising work towards personalized cone fundamentals.