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Published by Elsevier Ltd. This is an open access article under the CC BY license. Elsevier Vision Research Volume 162, September 2019, Pages 20-28 Vision Research The association between L:M cone ratio, cone opsin genes and myopia susceptibility Author links open overlay panelLene A.HagenaSolveigArnegardaJames A.KuchenbeckerbStuart J.GilsonaMaureenNeitzbJayNeitzbRigmor C.Baraasa Show more https://doi.org/10.1016/j.visres.2019.06.006Get rights and content Under a Creative Commons licenseopen access Highlights • Low myopia prevalence in Norwegian adolescents. • High mean L:M cone ratio in both Norwegian males and females. • High L:M cone ratios in females were associated with lower degree of myopia. • Myopia was more frequent in females heterozygous for L opsin exon 3 haplotypes. • Milder versions of L exon 3 skipping variants may play a role in common myopia. Abstract In syndromic forms of myopia caused by long (L) to middle (M) wavelength (L/M) interchange mutations, erroneous contrast signals from ON-bipolar cells activated by cones with different levels of opsin expression are suggested to make the eye susceptible to increased growth. This susceptibility is modulated by the L:M cone ratio. Here, we examined L and M opsin genes, L:M cone ratios and their association with common refractive errors in a population with low myopia prevalence. Cycloplegic autorefraction and ocular biometry were obtained for Norwegian genetically-confirmed normal trichromats. L:M cone ratios were estimated from spectral sensitivity functions measured with full-field ERG, after adjusting for individual differences in the wavelength of peak absorption deduced from cone opsin genetics. Mean L:M cone ratios and the frequency of alanine at L opsin position 180 were higher in males than what has been reported in males in populations with high myopia prevalence. High L:M cone ratios in females were associated with lower degree of myopia, and myopia was more frequent in females who were heterozygous for L opsin exon 3 haplotypes than in those who were homozygous. The results suggest that the L:M cone ratio, combined with milder versions of L opsin gene polymorphisms, may play a role in common myopia. This may in part explain the low myopia prevalence in Norwegian adolescents and why myopia prevalence was higher in females who were heterozygous for the L opsin exon 3 haplotype, since females are twice as likely to have genetic polymorphisms carried on the X-chromosome.