Estimation of heritability and familial correlation in myopia is not affected by past sun exposure

Purpose: To consider the effect of including past sun exposure in estimating heritability and familial correlation of myopia-related traits. Methods: We calculate the familial correlation and heritability of anterior chamber depth (ACD), axial length (AL), corneal curvature (CC) and spherical equivalent (SphE), with or without past sun exposure as a covariate, in a large number of unrelated nuclear families from the Raine Study (parents: Gen1, offspring: Gen2) residing in Perth, Australia, a city with a high amount of daily sunlight. Past sun exposure was objectively measured using conjunctival ultraviolet autofluorescence (CUVAF) photography. Results: When sun exposure was not included in the analysis, both familial correlation (correlation±SE; ACD: 0.308±0.065, AL: 0.374±0.061, CC: 0.436±0.063, SphE: 0.281±0.070) and heritability (ACD: 0.606±0.104, AL: 0.623±0.098, CC: 0.793±0.079, SphE: 0.591±0.106) were significant (all P < 0.001) for all traits. However, there was no significant change in both familial correlation and heritability estimates when sun exposure was included as an additional covariate. Conclusions: Past sun exposure does not affect the estimation of the additive genetic component in myopia-related traits.