Abstract
Abstract: :
Purpose: To estimate the prevalence of myopia in relatives of high myopes in a UK cohort, to calculate relative risk to siblings and to establish whether there is consistency with the dominant highly penetrant model for which putative high myopia loci have been identified. Methods: Of 218,410 patients attending optometric practices in the north of England, 2112 (1%) met our criteria for high myopia [refractive error in least minus meridian (LMMRx) of each eye ≥-6.00DS]. For a random group of these probands, we obtained data about the spectacle wearing status of their relatives by postal (n=159, 44% response) and telephone (n=135, 81% response) questionnaires. Age, sex and refractive status were the same for the respondent and non-respondent probands (Age p=0.15, Rx p=0.84). Age of onset of spectacle wear (AOSW) was used as a surrogate for degree of myopia in siblings of these highly myopic probands. Regression analysis of right eye LMMRx on loge AOSW for a cohort of myopic families participating in a separate genetic study at our lab (n=264, LMMRx -0.50DS to -20.75DS) indicated that an AOSW ≤ 9.4 ± 0.8 years would correspond to a LMMRx ≥ -6.00DS. Results: Prevalence of myopia (full time spectacle wear for myopia, FTSW) and a high myopia surrogate (AOSW ≤ 9.4 ± 0.8 years) in siblings of the highly myopic probands were markedly higher than population prevalence. Data shown in the table includes 95% confidence limits incorporating standard errors for the regression analysis and proportion estimates. The relative risk to siblings of high myopes was increased if one parent was a full time distance spectacle wearer (F=3.95, p=0.01), but no additional risk was conferred if this was true of both parents (F=0.09, p=0.92). Cases with no myopic parents were common (43.0%) and had a low (∼4%) sibling prevalence of our high myopia surrogate. Conclusion: High penetrance monogenic inheritance of high myopia as a discrete phenotype would predict a higher relative risk to siblings (λs) than our estimate. Observations in our cohort are more easily explained by the presence of phenocopies and/or additive polygenes along with heterogeneity.
Keywords: 481 myopia • 420 genetics