OPN1LW encodes the long-wavelength sensitive opsin protein, a key component of the visual phototransduction cascade in L-cone photoreceptors. This X-linked gene forms part of a complex gene cluster with OPN1MW at Xq28, where diverse haplotypes have arisen through unequal recombination mechanisms that intermix the genes 1. The protein functions as a G-protein coupled photoreceptor that mediates light absorption and initiates phototransduction signaling pathways essential for color vision and high acuity vision 2. Specific haplotypes containing five polymorphisms (p.L153M, p.V171I, p.A174V, p.I178V, and p.S180A) in exon 3 cause partial or complete exon skipping during pre-mRNA splicing, resulting in cones nearly devoid of photopigment 34. These splicing defects are associated with multiple vision disorders including blue cone monochromacy, protanopia, and high myopia 56. The gene's contribution to early-onset high myopia is substantial, accounting for variants in 5.5% of families with this condition, making it the second most common cause of monogenic early-onset high myopia 4. The complex structure of the OPN1LW/OPN1MW gene cluster requires specialized diagnostic approaches using long-read sequencing due to limitations of conventional short-read methods 7.