In normal tension glaucoma (NTG), intraocular pressure is within normal the range; thus, some mechanism other than increased pressure contributes to the optic neuropathy. Endothelin may be an important contributor to the development of the optic neuropathy characteristic of glaucoma. We investigated whether polymorphisms of the endothelin-1, endothelin receptor type A, and endothelin receptor type B genes were associated with NTG.

Sixty-seven Korean NTG patients and 100 healthy Korean subjects were enrolled. DNA from peripheral blood leukocytes was extracted and genotype distributions of six polymorphisms in genes encoding endothelin-1 (EDN1:c.-131dupA, EDN1:c.594G > T), endothelin receptor type A (EDNRA:c.-231G > A, EDNRA:c.*70C > G, EDNRA:c.*1222C > T), and endothelin receptor type B (EDNRB:c.831A > G) were determined. Genotype and allele distributions were compared between patients and controls. In NTG subjects, untreated baseline intraocular pressure and age at the time of diagnosis, as well as the mean deviation and pattern standard deviation values of automated static perimetry were examined for an association with these genetic polymorphisms.

The polymorphism of EDNRA:c.*1222C > T was significantly associated with NTG (p = 0.028, OR = 3.33, 95% CI 1.05-10.24). In addition, the AA genotype of the EDNRA:c.-231G > A polymorphism was associated with a lower baseline intraocular pressure than in the GG+GA genotype group (14.0 +/- 2.8 mm Hg versus 16.2 +/- 2.3 mm Hg, p = 0.047). No polymorphism was associated with visual field parameters.

A polymorphism of the endothelin receptor type A gene is associated with NTG.