Genetic and environmental factors in conjunctival UV autofluorescence

Conjunctival UV autofluorescence (CUVAF) photography was developed to detect and characterize preclinical sunlight-induced ocular damage. Ocular sun exposure has been related to cases of pterygia and was recently negatively correlated with myopia. Hence, CUVAF has excellent potential as an objective biomarker of sun exposure. However, much variation in CUVAF has been observed, and the relative contributions of genes and environment to this variation have not yet been identified.

To investigate sources of variation in CUVAF in relation to its potential clinical relevance.

We performed a cross-sectional analysis of 3 population-based cohort studies in the general community, including the Twins Eye Study in Tasmania, the Brisbane Adolescent Twin Study, and the Western Australian Pregnancy Cohort (Raine) Study. The twin studies were conducted between 2001 and 2009, and the 20-year follow-up of the Raine Study was completed between March 2010 and February 2012. We included genotypic and phenotypic data from 295 Australian families in the Tasmanian and Brisbane twin studies and from 661 participants in the 20-year follow-up of the Raine Study. We compared CUVAF levels in the 3 cohorts and performed a classic twin study to partition variation in CUVAF. We also conducted a genome-wide association analysis to identify specific genetic variants associated with CUVAF.

The total area of CUVAF, heritability of CUVAF, and single-nucleotide polymorphisms (SNPs) associated with CUVAF from the genome-wide association study.

Within twin cohorts, individuals living closer to the equator (latitude, 27.47° S) had higher levels of CUVAF compared with individuals from southern regions (latitude, 42.88° S) (median [interquartile range], 45.4 [26.8-68.5] vs 28.7 [15.0-42.3] mm2; P < .001). The variation in CUVAF explained by the additive genetic component was 0.37 (95% CI, 0.22-0.56), whereas the variation due to the common environment was 0.50 (95% CI; 0.29-0.71). The SNP rs1060043, located approximately 800 base pairs away from the SLC1A5 gene, a member of the solute carrier family 1, had a genome-wide significant association with a P value of 3.2 × 10-8. Gene-based analysis did not improve our power to detect association with other genes.

Our findings confirm that, although a large environmental component to CUVAF (equivalent of sun exposure) exists, genes also play a significant role. We identified a SNP (rs1060043) as being significantly associated with CUVAF; replication of this finding in future studies is warranted.