Cone opsins are expressed in cone photoreceptor cells and are required for color vision and visual acuity and function under photopic conditions. The cone opsins share about 40% sequence homology with rhodopsin ( Stenkamp et al., 2002). There are three human cone opsins: blue, green, and red cone opsins that correspond to OPN1SW, OPN1MW, and OPN1LW genes, respectively. In contrast to the oligomerization of rhodopsin, little is known about the oligomeric status of cone opsins. 1,11 However, its status as an independent clinical entity remains unclear. It has been argued that Bornholm eye disease differs from these common forms of dichromacy in which only red-green colour vision is affected but visual acuity is fully preserved. It is hypothesised that a skewed red (L-) to green (M-) cone ratio results in cone dysfunction if the most abundant cone subtype is inactivated by the above genetic changes. the state in which only two of the three cone subtypes are functional, either red (L-) and blue (S-) cones (deuteranopia) or green (M-) and blue (S-) (protanopia). It is worth highlighting that these genotypes have been described in isolated red-green dichromacy, i.e. Further investigation revealed rare genotypes in exon 3 of the OPN1LW gene (including the LIAVA variant combination discussed in the blue cone monochromatism section). Klaver, in Clinical Ophthalmic Genetics and Genomics, 2022 Bornholm eye diseaseīornholm eye disease was initially mapped to the OPN1LW and OPN1MW gene cluster on the X chromosome in the original Danish family.
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