A Meta‐analysis of stydies on the hetitability of myopia

Abstract Purpose Recently there has been considerable interest in the issue of mssing heritability ‐ the quite common problem of difficulty in matching the high heritability for some complex diseases with associated genomic variation. The aim of this analysis was to determine whether the heritability values for myopia and ocular biometry dervied from twin studies, broader family studies and population‐based studies were similar or different. Methods Relevant studies were collected by using as search words "myopia","refractive error", "axial length","corneal curvature", "corneal power" and "heritability" in the PubMed database. Reference lists of the papers identified were also searched to identify additional references. Studies on populations enriched in myopia or refractive error due to the selection criteria for inclusion were excluded from the analysis, Results The heritabilites determined for myopia from twin studies were significantly higher than those from family studies and population‐based studies. Fewer studies were availalbe on the heritability of axial length, but there appeared to be a similar trend in the data. Studies on the heritability of corneal power were even fewer in number, and the results were inconsistent. Conclusion The decline in the heritability of myopia with broader population base to the study suggests that the high heritability determined in twin studies is not generalisable, and may be associated with the low level of environmental variation within twin pairs. The heritability of axial length also depends on study design, although not as markedly as for myopia. Despite the high heritability determined in twin studies, evidence for major environmental effects is obtained with a broader population base.