Threat to fixation at diagnosis and lifetime risk of visual impairment in open-angle glaucoma.

Abstract

To investigate whether threat to fixation (TTF) at diagnosis increases the risk of central vision loss and glaucoma blindness. Retrospective cohort study. A total of 309 patients (309 eyes) with glaucoma were followed up until death; 203 patients (65.7%) had primary open-angle glaucoma, and 106 patients (34.2%) had exfoliation glaucoma. Study eyes were divided into 2 groups according to TTF in the first glaucomatous visual field: (1) eyes with TTF, defined as visual field loss (VFL) including ≥1 of the 4 innermost points depressed at P < 1% level in 24-2 or 30-2 Humphrey fields; (2) eyes without TTF, defined as VFL only outside the 4 innermost points. Lifetime risk of visual acuity (VA) loss and glaucoma blindness in the 2 groups was compared by logistic regression analysis. A matching technique was used to adjust for differences in disease stage at presentation. The relative influence of TTF on the risk of blindness in the 2 matched groups was analyzed by the Kaplan-Meier method. Visual acuity <0.3 and blindness from glaucoma (World Health Organization criteria) at last visit. Threat to fixation was detected in 58.9% of the eyes at diagnosis. The frequency of TTF increased with stage of glaucomatous loss: 28.3% in eyes with mean deviation (MD) >-6.00 decibels (dB) versus 95.7% with MD <-20.00 dB. Univariate analysis demonstrated that eyes with TTF at presentation compared with eyes without TTF became blind more often (56/182 [30.8%] vs. 22/127 [17.3%]; P = 0.008) and faster (mean time from diagnosis to blindness, 84.6±50.7 vs. 126.7±51.4 months; P < 0.002). However, in multivariate analysis, TTF was not an independent risk factor for VA <0.3 (odds ratio, 1.43; 95% confidence interval, 0.75-2.74) or blindness (odds ratio, 1.03; 95% confidence interval, 0.52-2.01). With regard to patient survival time, there were no differences between eyes with TTF and eyes without TTF after adjusting for disparities in disease severity at presentation (P = 0.934). Including TTF in the assessment of risk for glaucoma blindness did not add any important information when the stage of VFL was taken into account.