VDR rs731838: Genetic Variation and Refractive Error
The rs731838 variant is an intronic single nucleotide polymorphism located within the vitamin D receptor (VDR) gene on chromosome 12. In candidate gene studies, it has been evaluated for potential associations with ocular axial length elongation and susceptibility to high myopia. However, overall scientific evidence remains limited, with broader genome-wide association studies showing mixed or inconclusive findings.
What each genotype means
Typical axial length risk
You carry two copies of the C allele for rs731838. In candidate genetic studies evaluating the vitamin D receptor (VDR) gene and refractive error, this genotype is considered the baseline or non-risk profile for axial length elongation and high myopia. However, overall evidence linking VDR polymorphisms to myopia is limited and has shown inconsistent results across different ancestry cohorts.
Carried by approximately 30% to 45% of individuals globally, with varying frequencies across populations.
Intermediate myopia susceptibility
You carry one copy of the T allele associated in some preliminary research with variations in axial eye growth and myopia susceptibility. Because this variant is intronic and evidence across independent replication studies remains limited and mixed, having this genotype confers at most a modest statistical association rather than a definitive prediction of refractive error.
Found in roughly 45% to 50% of individuals in most ancestral populations as the common heterozygous state.
Modestly increased myopia susceptibility
You carry two copies of the T allele for rs731838, which some candidate gene analyses have linked to increased risk of axial elongation and high myopia compared to the CC genotype. Published evidence remains limited, and large population-based cohorts have observed inconsistent replication of VDR variant associations with refractive error. Refractive development is multifactorial and strongly shaped by visual environment, near work, outdoor time, and numerous polygenic loci.
Carried by roughly 12% to 20% of individuals across global populations.
Genomic Location and Variant Characteristics
The single nucleotide polymorphism rs731838 sits on chromosome 12 within an intronic region of the VDR gene. Because it resides in an non-coding intron rather than altering the amino acid sequence directly, it does not alter the fundamental structure of the protein. Instead, researchers categorize it as a putative regulatory variant or genetic marker that may correlate with differential transcription, mRNA stability, or alternative splicing mechanisms. In many human genetic studies, intronic variants like rs731838 serve as proxy tags that track in linkage disequilibrium alongside other functionally relevant changes across the vitamin D receptor locus. Genomic repositories such as dbSNP catalogue the standard nucleotide variation between the cytosine (C) and thymine (T) alleles at this site, providing a baseline for population-level frequency mapping.
The Biological Role of the Vitamin D Receptor
The VDR gene encodes the vitamin D receptor, a member of the nuclear steroid and thyroid hormone receptor superfamily. When activated by its primary ligand, 1,25-dihydroxyvitamin D3 (calcitriol), the receptor forms a heterodimer with the retinoid X receptor (RXR) and translocates to the nucleus to bind vitamin D response elements in genomic DNA. This pathway orchestrates systemic calcium and phosphate homeostasis, mineral metabolism, and cellular differentiation. In the eye, vitamin D receptors are expressed in ocular tissues including the retina, choroid, and sclera. Extracellular matrix remodeling in the sclera directly controls the axial elongation of the eyeball, providing a theoretical biological pathway through which variations in vitamin D signaling might influence scleral tensile strength and shape development.
Scientific Evidence and Myopia Associations
Multiple candidate gene association studies have investigated whether polymorphisms within the VDR gene, including rs731838, alter susceptibility to refractive errors and excessive axial length elongation characteristic of high myopia. While early targeted studies reported modest statistical correlations between specific alleles and myopia risk, large-scale genome-wide association studies (GWAS) and birth cohort investigations (such as studies from the ALSPAC cohort) have observed mixed or non-significant results. The evidence strength linking rs731838 to refractive traits is formally categorized as limited. Myopia is a classic complex polygenic trait influenced by hundreds of small-effect genomic loci working in combination with environmental pressures, most notably time spent outdoors in natural sunlight and sustained near-work activity during childhood.
Interpreting Results in Clinical Context
A genotype at rs731838 cannot diagnose, predict, or confirm myopia, nor does it establish an individual's systemic vitamin D levels. Because its effect size is minor and inconsistent across diverse ancestries, personal genetic testing for this single marker has no validated clinical utility in ophthalmic practice. Individuals concerned about refractive errors or visual changes should rely on standard comprehensive eye examinations by an optometrist or ophthalmologist rather than single-locus genetic profiles. Furthermore, while sunlight exposure is an established protective environmental factor against childhood myopia onset, this protective benefit operates through complex physiological retinal signaling rather than direct single-gene mutations. No adjustments to diet, lifestyle, or supplementation should be made solely based on an rs731838 genotype.
How common is this variant?
The rs731838 variant is widely distributed across global populations, with the minor allele frequency typically ranging between 0.35 and 0.45 across diverse cohorts catalogued in gnomAD and dbSNP.
Frequently asked questions
Does having the rs731838 variant mean I will develop high myopia?
No. The rs731838 variant has only a limited and inconsistent association with refractive error. Myopia is a complex condition driven by hundreds of genes along with environmental factors like screen time and outdoor light exposure.
Can taking vitamin D supplements prevent myopia if I carry this variant?
There is no clinical evidence that taking dietary vitamin D supplements prevents or treats myopia. While time spent outdoors is protective against childhood myopia, that benefit is related to ambient light intensity and ocular dopamine release rather than oral vitamin supplementation.
Where is the rs731838 variant located in the genome?
It is an intronic variant located within the VDR gene on human chromosome 12. Because it is intronic, it does not directly alter the protein's amino acid sequence.
How common is the rs731838 polymorphism?
It is a very common genetic variant found across worldwide populations, with allele frequencies generally hovering between 35% and 45%.
Sources & further reading
Educational information only, last refreshed 9/14/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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