A validated risk calculator to assess risk and rate of visual field progression in treated glaucoma patients

Abstract

Purpose: The purpose of our study is to develop and validate a model to predict visual field (VF) outcomes in patients with treated glaucoma.

Methods: Data from 587 eyes with treated glaucoma evaluated in a cohort were used to develop two equations to predict VF outcomes, one estimating the risk of progression (%) and another estimating the global rate of VF sensitivity change (decibels [dB]/year). These equations, which included variables associated with VF progression in a multivariable model, then were tested in another cohort (n = 62 eyes) followed for at least 4 years. Agreement, discrimination, and calibration of the model in the validation sample were assessed as main outcome measures.

Results: The mean difference between observed and predicted global rates of sensitivity change was 0.13 dB/year (95% confidence interval [CI] = 0.06 to 0.18 dB/year) and the mean difference between observed and predicted final VF mean deviation (MD) values was 0.37 dB (95% CI = 0.00 to 0.75 dB). The predictive model had moderate discriminative ability to estimate VF progression in the independent sample (c-index of 0.78, 95% CI = 0.59 to 0.97).

Conclusions: To our knowledge, this is the first attempt to generate and validate a risk model for patients with treated glaucoma. The prediction model showed moderate accuracy in estimating future VF outcomes in an independent glaucoma population, and may be useful for the objective assessment of risk of progressive VF loss.

Figure 1

(A) The Bland-Altman plot illustrates the difference between the observed and predicted rates of visual field progression (y-axis) and their average (x-axis). The green dashed line corresponds to the 95% CI of the mean difference (0.06–0.18 dB). The red dashed line corresponds to the 95% limits of agreement (mean ± 1.96 SD, −0.35–0.61 dB). The orange dotted line in the middle represents the zero difference. (B) The Bland-Altman plot illustrates the difference between the observed and the predicted final MD values (y-axis) and their average (x-axis). The green dashed line corresponds to the 95% CI of the mean difference (0.00–0.75 dB). The red dashed line corresponds to the 95% limits of agreement (mean ± 1.96 SD, −2.56 to 3.31 dB). The orange dotted line in the middle represents the zero difference.

Figure 2

(A) For the subset of eyes with 10 or more visual field tests, the Bland-Altman plot illustrates the difference between the observed and predicted rates of visual field progression (y-axis) and their average (x-axis). The green dashed line corresponds to the 95% CI of the mean difference (0.06–0.19 dB). The red dashed line corresponds to the 95% limits of agreement (mean ± 1.96 SD, −0.21–0.47 dB). The orange dotted line in the middle represents the zero difference. (B) For the subset of eyes with 10 or more visual field tests, the Bland-Altman plot illustrates the difference between the observed and predicted final MD values (y-axis) and their average (x-axis). The green dashed line corresponds to the 95% CI of the mean difference (−0.05–1.04 dB). The red dashed line corresponds to the 95% limits of agreement (mean ± 1.96 SD, −2.28–3.27 dB). The orange dotted line in the middle represents the zero difference.

Figure 3

Calibration plots of prediction of glaucoma progression based on our PLR criteria (two adjacent points in the same hemifield progressing faster than −1.0 dB/year at P < 0.01). The x-axis refers to the quartile of predicted risk based on our risk model. The y-axis refers to the observed frequency of eyes meeting PLR progression criteria within each quartile.

Figure 4

Comparison of the distribution of global rates of visual field sensitivity change (dB/year) between observed and predicted values in the validation sample. The x-axis corresponds to quartiles based on predicted global rates of progression (dB/year). The y-axis refers to the mean rate of progression within each quartile for observed and predicted values (very fast = −0.71 to −1.13, fast = −0.62 to −0.70, moderate = −0.51 to −0.61, slow = −0.33 to −0.50).