Association of vitamin D receptor gene start codon [Fok 1] polymorphism with high myopia

ABSTRACT

High myopia caused primarily due to abnormal emmetropization and excessive axial ocular elongation is associated with sight-threatening ocular pathology. Muscular dysfunction of ocular ciliary muscles due to altered intracellular calcium levels can result in defective mechanotransduction of the eye and retinal defocus. The vitamin D3 receptor [VDR; a intracellular hormone receptor] is known to mediate calcium homestasis, influencing the development of myopia. In the present study, a total of 206 high myopia, 98 low myopia and 250 control samples were analyzed for VDR gene Fokl [exon 2 start codon] polymorphism using polymerase chain reaction-restriction fragment length polymorphism [PCR-FRLP] technique. High myopia patients revealed decrease in the frequency of ff homozygotes [8.3%] as compared to control group [14.0%], with a corresponding increase in frequency of FF homozygotes [68.9% in high myopia vs. 62.8% in controls]. The frequency of fallele carriers [Ff and ff] was increased in females of high myopia [35.6%] and low myopia cases [45.4%]. Elevated frequency of f allele was found only in early age at onset cases of high myopia [0.227] and later age at onset [10- 20 years] cases of low myopia [0.273] as well as in low myopia cases with parental consanguinity [0.458] [P 0.035; chi [2] = 6.692[*]]. The results suggest that VDR gene might not be playing a direct role in the development conferred by mechanical stress factors or growth/ development related factors through its role in calcium homestasis and regulation of ciliary muscle function