title: Association of vitamin D receptor gene start codon (Fok1) polymorphism with high myopia.
abstract: BACKGROUND
  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 homeostasis, influencing the development of myopia.
  
  
  METHODS
  In the present study, a total of 206 high myopia, 98 low myopia and 250 control samples were analyzed for VDR gene Fok1 (exon 2 start codon) polymorphism using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique.
  
  
  RESULTS
  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 f allele 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; χ(2) = 6.692*).
  
  
  CONCLUSIONS
  The results suggest that VDR gene might not be playing a direct role in the development of myopia, but might contribute indirectly to the risk conferred by mechanical stress factors or growth/development related factors through its role in calcium homeostasis and regulation of ciliary muscle function.
authors: Department of Genetics, Osmania University, Hyderabad 500 007, India.
authors: Sandhya
authors: S
authors: Annamaneni
authors: Chintala Hema
authors: CH
authors: Bindu
authors: Kasu Prasad
authors: KP
authors: Reddy
authors: Satti
authors: S
authors: Vishnupriya