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September 2002

When Does Information Become Medically Useful?The Role of Genetic Testing in Glaucoma

Arch Ophthalmol. 2002;120(9):1204-1205. doi:10.1001/archopht.120.9.1204

IN THIS ISSUE of the ARCHIVES, Alward and coworkers1 describe the prevalence of "plausible disease causing-sequence variations(DCVs) in the MYOC [myocilin] gene" among a large unselected group of consecutive patients with a variety of open-angle glaucomas in a tertiary glaucoma practice. Their finding that DCVs occur in approximately 3% and 6% of patients with adult-onset primary open-angle glaucoma (POAG) and with juvenile open-angle glaucoma (JOAG), respectively, confirms findings from earlier reports.2-4 None of the normal subjects exhibited DCVs in the myocilin coding sequence. If a new commercially available product, the OcuGene Test (Insite Vision, Alameda, Calif) had been used to screen this population, none of the 13 patients with adult-onset POAG with DCVs would have been detected. The OcuGene test also determines the presence of a polymorphism in the promoter region of the myocilin gene (MYOC.mt1) that has recently been described by Colomb and colleagues5 as being an indicator of disease severity and resistance to drug therapy. Like the Colomb et al study, Alward and coworkers found no higher prevalence of the MYOC.mt1 promoter polymorphism in patients with POAG than in normal subjects without glaucoma. The MYOC.mtl promoter polymorphism was found in 61 (15.5%) of 393 patients with adult-onset POAG and in 22 (23.9%) of 92 normal subjects. The Colomb study reported somewhat worse visual field loss and higher treated intraocular pressures (IOPs) among those with the MYOC.mtl promoter polymorphism. In contrast, the Alward study found no differences in severity of disease among women or men with either heterozygous or homozygous alleles for the promoter polymorphism. While the 2 studies used different quantitative measures of disease severity, those employed by Alward and colleagues are more familiar to most ophthalmologists. The fact that Alward et al failed to find any added risk from the MYOC.mtl promoter polymorphism in a much larger population than that of Colomb and coworkers raises doubts that this polymorphism is substantially related to the severity of glaucomatous damage for most patients.

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