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Jelle Vehof, Diana Kozareva, Pirro G. Hysi, Christopher J. Hammond; Heritability of dry eye disease. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1281.
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© ARVO (1962-2015); The Authors (2016-present)
To estimate the relative importance of genes in dry eye disease (DED) in a classic twin study.
304 pairs of female twins (122 monozygotic and 182 dizygotic) were studied, who were on average 61.2 years old (sd, 9.2). Participants were recruited from the St. Thomas’ UK Adult Twin Registry and have been shown to be population-representative. DED symptoms were evaluated by the Ocular Surface Disease Index (OSDI) questionnaire. DED signs were measured by a Schirmer score (mean value of both eyes), tear osmolarity (TearLab Osmolarity System, San Diego, Ca) (mean value of both eyes), tear breakup time (mean value of both eyes), blink rate and the presence of signs of anterior blepharitis and meibomian gland dysfunction. In addition, a large sample (1595 female twin pairs) was questioned about the presence of a DED diagnosis by a clinician, the prescription of eye drops and the presence of DED complaints in the last three months. Heritability was estimated using maximum likelihood structural equation modeling with the program Mx for quantitative traits, and using case-wise concordances for dichotomous traits.
Prevalence of DED ranged from 10.4% (diagnosis by a clinician) to 19.3% (DED complaints in the last three months). 13.8% of participants has ever been prescribed an eye drop. DED symptoms and signs were similar for monozygotic and dizygotic twins. Estimates of the heritability of quantitative DED signs were 31% (95% CI 8-50%) for Schirmer scores, 37% (95% CI 21-50%) for tear osmolarity, and 29% (95% CI 13-43%) for blink rate; we found no significant heritability for tear breakup time. Genetic evidence for anterior blepharitis was found as signs were more concordant in MZ than in DZ twins (case-wise concordance 0.49 and 0.34 respectively, ratio 1.4), though this was less for meibomian gland dysfunction (0.87 and 0.82 respectively, ratio 1.1). The estimates of heritability for DED symptoms were lower: 19% (95% CI 3-34%) for the OSDI score, and concordance rates of 0.33 versus 0.27 (ratio 1.2) for DED complaints in the last three months. DED diagnosis by a clinician and the prescription of eye drops showed more suggestive evidence of genetic influence with concordance rates of 0.31 versus 0,20 (ratio 1.5), and 0.27 versus 0.17 (ratio 1.6), respectively.
Genetic factors contribute to the ocular signs of DED -explaining 30 to 40% of the variance- and to the diagnosis of DED. Compared to other ocular phenotypes, the lower heritability might reflect some of the difficulties in objective phenotyping and diagnosis of DED in a population-based sample.
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