Predicting Vision-Related Disability in Glaucoma

Abstract

Purpose: To present a new methodology for investigating predictive factors associated with development of vision-related disability in glaucoma.

Design: Prospective, observational cohort study.

Participants: Two hundred thirty-six patients with glaucoma followed up for an average of 4.3±1.5 years.

Methods: Vision-related disability was assessed by the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25) at baseline and at the end of follow-up. A latent transition analysis model was used to categorize NEI VFQ-25 results and to estimate the probability of developing vision-related disability during follow-up. Patients were tested with standard automated perimetry (SAP) at 6-month intervals, and evaluation of rates of visual field change was performed using mean sensitivity (MS) of the integrated binocular visual field. Baseline disease severity, rate of visual field loss, and duration of follow-up were investigated as predictive factors for development of disability during follow-up.

Main outcome measures: The relationship between baseline and rates of visual field deterioration and the probability of vision-related disability developing during follow-up.

Results: At baseline, 67 of 236 (28%) glaucoma patients were classified as disabled based on NEI VFQ-25 results, whereas 169 (72%) were classified as nondisabled. Patients classified as nondisabled at baseline had 14.2% probability of disability developing during follow-up. Rates of visual field loss as estimated by integrated binocular MS were almost 4 times faster for those in whom disability developed versus those in whom it did not (-0.78±1.00 dB/year vs. -0.20±0.47 dB/year, respectively; P < 0.001). In the multivariate model, each 1-dB lower baseline binocular MS was associated with 34% higher odds of disability developing over time (odds ratio [OR], 1.34; 95% confidence interval [CI], 1.06-1.70; P = 0.013). In addition, each 0.5-dB/year faster rate of loss of binocular MS during follow-up was associated with a more than 3.5 times increase in the risk of disability developing (OR, 3.58; 95% CI, 1.56-8.23; P = 0.003).

Conclusions: A new methodology for classification and analysis of change in patient-reported quality-of-life outcomes allowed construction of models for predicting vision-related disability in glaucoma.

Figure 1.

A) Distribution of values of baseline mean deviation (MD) of the better eye in subjects who were non-disabled at baseline but developed disability during follow-up versus those from subjects who remained non-disabled during follow-up. B) Distribution of values of total change in mean deviation (MD) over time of the better eye in subjects who were non-disabled at baseline but developed disability during follow-up versus those from subjects who remained non-disabled during follow-up. C) Distribution of rates of change in the integrated binocular field mean sensitivity (MS) over time for subjects who developed disability versus those who remained non-disabled during follow-up.

Figure 2.

The relationship between probability of developing disability during follow-up and rates of change in integrated binocular mean sensitivity (MS). Faster rates of change were associated with higher probabilities of disability. The graph also shows that subjects with worse baseline MS had overall higher probabilities of developing disability.

Figure 3.

The relationship between increase in probability of developing visual disability during follow-up and rates of visual field change in binocular mean sensitivity (MS) varied according to baseline disease severity. For subjects with worse disease severity, there was a greater impact of rates of change in increasing the probability of disability.