Family aggregation of high myopia: estimation of the sibling recurrence risk ratio.

PURPOSE: To estimate the sibling recurrence risk (KS) and the sibling recurrence risk ratio (lambda(S)) for high myopia in a cohort in the United Kingdom.
METHOD: The recurrence risks for myopia and high myopia were estimated in the siblings of 296 randomly selected high myopes ascertained from an optometric practice population. A model using an age of onset of spectacle wear for myopia of 9.1 +/- 0.7 years or younger was developed as a surrogate for high myopia. The influence of parental myopia on the sibling recurrence risk for high myopia was also evaluated.
RESULTS: KS was estimated (95% confidence limits) to be 10.0% (5.9, 14.8) and lambdaS to be 4.9 (2.8, 7.6). High myopes without myopic parents were surprisingly common ( approximately 40%) and were less likely to have highly myopic siblings (KS approximately 6%) than those with at least one myopic parent (KS approximately 14%).
CONCLUSIONS: The sibling recurrence risk ratio reported herein (lambdaS approximately 4.9) implies that the high penetrance autosomal dominant loci for high myopia identified to date account for only a minority of cases of high myopia in the United Kingdom. Furthermore, high-penetrance autosomal dominant inheritance or even high-penetrance recessive inheritance, per se, cannot account for most cases of high myopia. Instead, it may be necessary to consider high myopia as a "complex disease" resulting from the influence of either alleles of reduced penetrance ("susceptibility genes"), environmental factors, or both. Copyright Association for Research in Vision and Ophthalmology