Significant Variation of the Elevated Nitric Oxide Levels in Aqueous Humor from Patients with Different Types of Glaucoma

Abstract

Though several studies have shown that the biochemical function of nitric oxide (NO) in the eye might play an important role in the regulation of intraocular pressure (IOP), local control of ocular blood flow and loss of retinal ganglion cells by apoptosis, it is unclear whether the role of NO is similar in the pathogenesis of different kinds of glaucoma: primary open-angle glaucoma (POAG), chronic closed-angle glaucoma (CCAG) and neovascular glaucoma (NVG). To further explore this issue, we measured the concentrations of NO in aqueous humor and plasma samples from patients with POAG (n = 31), CCAG (n = 76), NVG (n = 8) and cataract (n = 30). All of the NVG patients suffered from severe proliferative diabetic retinopathy, while other patients were free of any other systemic disease. The NO levels in both aqueous humor and plasma samples were assessed by chemiluminescence assay. We found that the NO levels in aqueous humor samples were greatly varied in patients with POAG (36.2 ± 3.3 µM), CCAG (47.7 ± 3.4 µM) and NVG (65.8 ± 5.4 µM), and all of them were significantly higher than in cataract patients (27.0 ± 2.9 µM; p < 0.05). Except NVG patients whose NO levels in plasma samples were highest (24.1 ± 3.5 µM) among all groups, the plasma NO levels were not significantly different between the other glaucoma patients and the cataract patients. We therefore concluded that significant variation of the elevated NO levels in aqueous humor samples from the patients with different types of glaucoma may reflect their differences in the pathogenesis.