Abstract
Purpose :
Selenium is an essential trace element, which once ingested is incorporated into antioxidant enzymes that prevent cellular damage. However, clinical studies have identified excess selenium levels in plasma and aqueous in patients with glaucoma. Given reported benefits of selenium supplementation in thyroid-associated ophthalmopathy, we aimed to evaluate whether dietary selenium, iodine, and prescribed medication for thyroid dysfunction were associated with glaucoma-related endophenotypes in the general population.
Methods :
Participants from the TwinsUK registry were recruited. Firstly, energy-adjusted selenium and iodine intake from 1,977 individuals was estimated through a validated food frequency questionnaire(FFQ). Secondly, self-reported prescribed thyroid medication use was recorded for 1,234 twins. Endophenotypes evaluated included intraocular pressure (IOP), retinal nerve fibre layer (RNFL) thickness and vertical cup to disc ratio (VDCR) adjusted for disc area. Linear mixed models investigated associations of individual nutrients and endophenotype after stratifying intake into quartiles. Logistic regression modelling evaluated use of thyroid hormone medication and IOP > 21mmHg, VCDR > 0.7 and RNFL< 90µm. All models were adjusted for age, sex, spherical equivalent (SE) and family structure.
Results :
Mean(SD) age was 62.1(12.25). Mean endophenotype values were IOP: 13.3mmhg(2.82), VCDR: 0.4(0.14) and RNFL: 95.1µm(10.10). Dietary iodine was not associated with any endophenotypes. Multivariate regression models evaluating lowest versus highest quartiles of dietary intake of selenium identified an effect of high selenium intake on VCDR (β=0.02,p=0.04) and a trend towards a thinner RNFL(β=-1.28, p=0.068). IOP was not associated with selenium uptake(β=0.23, p=0.279). The use of oral thyroid hormone medication was associated with a greater risk of having an RNFL thickness less than 90µm (odds ratio (OR):1.67,p=0.001), and non-significant odds ratios of having an IOP>21mmHg (OR:1.30,p=0.80) or a VCDR >0.7(OR:1.26,p=0.83).
Conclusions :
In a healthy population, higher levels of dietary selenium appear to be related to a larger VCDR and oral thyroid medication is associated with a greater risk of having a thin RNFL. Larger longitudinal studies are required to replicate these results and determine whether hypothyroid patients and individuals with high selenium intakes are at greater risk of glaucoma.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.