Abstract
Purpose: :
To evaluate whether the refractive error affects the difference of inter-ocular glaucoma severity in patients with normal tension glaucoma (NTG).
Methods: :
We retrospectively evaluated all glaucoma patients who were diagnosed NTG for the first time in our hospital from March 2006 to September 2009. The patients were divided into 2 groups according to spherical equivalent of both eyes : hyperopia ( > +0.25D) and myopia ( < -0.25D). In each group, we investigated relationships between the differences of inter-ocular Humphrey visual field MD (mean deviation) and bilateral differences of ocular parameters, including refractive error, intraocular pressure (IOP), and central corneal thickness (CCT) using multiple linear regression analysis. In addition, the further evaluation was performed in myopic patients who had bilateral NTG with more than 2dB difference of MD.
Results: :
There were 246 NTG patients (492 eyes, mean age : 58.79 ± 12.87, 123 male). In hyperopic patients (N=102), there were no statistically significant between inter-ocular differences of MD and bilateral differences of refractive error (P = 0.25). However in myopic patients (N=109), univariate analysis showed that bilateral differences of refractive error (β = 1.91, P < 0.0001) and CCT (β = 0.096, P = 0.048) were statistically significant. Bilateral differences of refractive error (β = 1.63, P = 0.0003) were also statistically significant with multivariate analysis. Besides in myopic patients who had bilateral NTG with more than 2 dB differences of MD (N=55), bilateral differences of refractive error (β = 1.61, P = 0.0249) were statistically significant with multivariate analysis, either.
Conclusions: :
In myopic patients with normal tension glaucoma, bilateral difference of refractive error may affect the difference of inter-ocular glaucoma severity.
Keywords: myopia • visual fields • intraocular pressure