Low serum 25-hydroxyvitamin D is not associated with myopic refractive error in Western Australian older adults

Abstract

Purpose : The prevalence of myopia is increasing world-wide; however the factors driving this increase are not well understood. Low serum 25-hydroxyvitamin D (25[OH]D) levels have been associated with increased myopic refractive error in children and adults, however recent studies have found no association after adjustment for sun exposure. We investigated the association between refractive error and serum 25[OH]D in Western Australians aged 45 to 64 years residing in a rural, coastal shire at approximately 34°S latitude.

Methods : Between 2010 and 2015, 5107 participants of the Busselton Healthy Ageing Study underwent cycloplegic autorefraction (ARK-30, Nidek) and completed questionnaires on medical history, demographics and physical activity. Serum 25[OH]D levels were measured by immunoassay (ARCHITECT, Abbott) from blood samples collected on the day of examination. Deseasonalised 25[OH]D values (according to month of collection) were categorised into Lower (<50nmol/L), medium (≥50 to <75nmol/L), and higher (≥75nmol/L). Participants who had missing refraction or 25[OH]D date were excluded as were those who identified as non-Caucasian, or self-reported a history of cataract diagnosis, laser refractive surgery or keratoconus. The association between right eye spherical equivalent and deseasonalised serum 25[OH]D was analysed using linear regression.

Results : After exclusions, data were available for 4463 (87.4%) participants. Mean age was 57.60 years (SD 5.71) and 54.4% were female. There was no significant association between 25[OH]D and spherical equivalent before or after adjustment for age, sex, education, occupational sun exposure, retirement, use of cycloplegia, and hours spent sitting per day (β=-2.9×10^-4, p=0.77 and β=-6.7×10^-4, p=0.50, respectively). Serum 25[OH]D category demonstrated a mild, significant inverse U-shaped relationship with spherical equivalent (p<0.001), where the higher 25[OH]D category had the most myopic refraction, while the medium group had the least.

Conclusions : Contrary to previous studies, participants in our study who had more myopic refractive error did not have lower serum 25[OH]D levels. Serum 25[OH]D level in older adults residing in a sunny, coastal environment was not associated with refractive error in this cross-sectional study.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.