Predictors Of Visual Acuity in Primary Open Angle Glaucoma Patients Participating in the Indianapolis Glaucoma Progression Study

Abstract

Purpose: : To explore the predictors of worsening visual acuity in patients with primary open angle glaucoma (OAG).

Methods: : 116 patients (mean age 66.9 +/- 10.9, 70 female) with OAG participating in the Indianapolis Glaucoma Progression Study (IGPS) were assessed for visual acuity and intraocular pressure (IOP). Peak systolic (PSV) and end-diastolic velocity (EDV) of the ophthalmic artery (OA), central retinal artery (CRA), and nasal and temporal posterior ciliary arteries (NPCA and TPCA) were measured by color Doppler imaging (CDI). Average retinal nerve fiber layer (RNFL) thickness was measured by optical coherence tomography. Bivariate correlations between variables were described by Spearman rank-correlation coefficient (rho). Mann-Whitney U test was used to compare RNFL thickness between genders. Multivariate linear regression analysis was performed with rank-transformed data to obtain the partial correlation coefficient (partial rho) adjusted for the effects of covariates. Colinearity statistics and diagnostics were checked. Independent variables with strong inter-correlations (r= 0.7) were not used together in the same regression model.

Results: : Bivariate analysis revealed that logMAR visual acuity positively correlated with age (r=0.505 , P<0.001 ) and negatively correlated with OA PSV (r= -0.183, P= 0.049) and EDV (r=-0.277, P= 0.003). There were weak negative associations between logMAR visual acuity and IOP (r= -0.157, P = 0.091) and average RNFL thickness (r= -0.164, P= 0.078). Women were found to have a higher logMAR visual acuity than men (P= 0.013)To evaluate the independent association of the different variables with logMR visual acuity, we examined the multivariate regression analysis and obtained a model with age, gender, IOP, OA PSV and EDV, and average RNFL thickness as independent variables. The model explained 33.3% of variance in logMAR visual acuity among the studied population. LogMAR visual acuity was independently associated with age (partial rho= 0.487, P< 0.01), female gender (partial rho= -0.336, P< 0.01) and OA PSV (r= -0.193, P = 0.043).

Conclusions: : In patients with OAG participating in the IGPS, increasing age, female gender and low OA blood flow velocities were important predictors of visual acuity decline.

Keywords: visual acuity • aging: visual performance • blood supply