• potineurin
• glaucoma
• M98K

• POAG, primary open angle glaucoma
• IOP, intraocular pressure
• NTG, normal tension glaucoma
• OPTN, OPTINEURIN
• PCR, polymerase chain reaction

Primary open angle glaucomas (POAGs) are the commonest form of glaucoma among Caucasians. They are defined by an excavation of the optic nerve head, a progressive loss of the visual field, and a normally open iridocorneal angle.¹ Their prevalence is 1–2% and they are a major cause of irreversible blindness in Western countries.² Albeit not necessary to the definition of POAG, an elevation of intraocular pressure (IOP) is a major contributory factor, and its lowering is at present the only available therapeutic strategy. In a subset of POAG patients, however, the IOP remains in the normal range—that is, less than 21 mm Hg, defining normal tension glaucoma (NTG).³ Whether NTG constitutes a pathological entity distinct from POAG is debated.⁴

Genetic factors play a major role in POAG predisposition. The genetic basis of POAG, is complex and heterogeneous.⁵ Recently, the OPTINEURIN (OPTN) gene on chromosome 10p14 was shown to be implicated in NTG.⁶ Mutations in this gene were found to segregate in nine out of 54 families with dominantly inherited POAG and normal or moderately elevated IOP. A variant, M98K, was associated with an increased absolute risk of 13.6% in a group of 169 POAG patients with normal or elevated IOP, compared with a relative allele frequency of 2.1% in a control population.⁶ This observation has made the M98K variant the potentially most important single genetic factor contributing to POAG predisposition. It is therefore essential to assess its role in different populations. In the present study, we evaluated the M98K variant in two groups of POAG patients, one from France and the other from Morocco, with population matched controls.