Comparison of risk factors for bilateral and unilateral eye involvement in normal-tension glaucoma.

PURPOSE To compare the risk factors for bilateral and unilateral disease in normal-tension glaucoma (NTG). METHODS The study analyzed data from consecutive NTG patients with either bilateral (n = 194) or unilateral (n = 193) disease. Multivariate regression models were used to evaluate the following potential risk factors for bilateral eye involvement: age, sex, central corneal thickness, mean deviation in standard automated perimetry, mean and fluctuation of diurnal intraocular pressure (IOP) without glaucoma medication, spherical equivalent, family history of glaucoma, and underlying systemic disease such as diabetes mellitus, hypertension, hypercholesterolemia, ischemic heart disease, previous cerebrovascular accident, migraine, and cold extremities. RESULTS Multivariate analysis showed that worse mean deviation in the first affected eye (odds ratio [OR], 1.19/1 dB decrease; P < 0.001), diabetes mellitus (OR, 2.31; P = 0.004), previous cerebrovascular accident (OR, 4.27; P = 0.039), and mean IOP greater than 14 mm Hg in the less affected eye (OR, 1.66; P = 0.030) were significantly associated with bilateral eye involvement in NTG. CONCLUSIONS Besides being an indicator of disease severity (worse mean deviation), diabetes mellitus, previous cerebrovascular accident, and IOP were associated with bilateral eye involvement. These data suggest that systemic vascular factors and IOP play significant roles in the pathogenesis of NTG. It appears that although systemic vascular factors increase the susceptibility of the optic nerve, a certain level of pressure-induced stress is also required to cause glaucomatous optic neuropathy.