EVIDENCE THAT A LOCUS FOR FAMILIAL HIGH MYOPIA MAPS TO CHROMOSOME 18P

Myopia, or nearsightedness, is the most common human eye disorder. A g enomewide screen was conducted to map the gene(s) associated with high , early-onset, autosomal dominant myopia. Eight families that each inc luded two or more individuals with greater than or equal to-6.00 diopt ers (D) myopia, in two or more successive generations, were identified . Myopic individuals had no clinical evidence of connective-tissue abn ormalities, and the average age at diagnosis of myopia was 6.8 years. The average spherical component refractive error for the affected indi viduals was -9.48 D. The families contained 82 individuals; of these, DNA was available for 71 (37 affected). Markers nanking or intragenic to the genes for Stickler syndrome types 1 and 2 (chromosomes 12q13.1- q13.3 and 6p21.3, respectively), Marfan syndrome (chromosome 15q21.1), and juvenile glaucoma (chromosome 1q21-q31) were also analyzed. No ev idence of linkage was found for markers for the Stickler syndrome type s 1 and 2, the Marfan syndrome, or the juvenile glaucoma loci. After a genomewide search, evidence of significant linkage was found on chrom osome 18p. The maximum LOD score was 9.59, with marker D18S481, at a r ecombination fraction of .0010. Haplotype analysis further refined thi s myopia locus to a 7.6-cM interval between markers D18S59 and D18S113 8 on 18p11.31.