Are rates of vision loss in patients in English glaucoma clinics slowing down over time? Trends from a decade of data

Abstract

Purpose: To examine changes in rates of visual field (VF) progression in patients attending a sample of glaucoma clinics in England between 1999 and 2012.

Methods: An archive of 473 252 Humphrey VFs recorded across the UK was retrospectively examined. Distribution of rates recorded in the first half of the decade was compared with the second. The relationship between age and severity of MD loss at baseline with rates of loss and frequency of testing was examined.

Results: VF series from 18 926 eyes were analysed. Median rate of MD loss for the period before and after 2003 was -0.11 and -0.06 dB/year, respectively, but the proportion of eyes with medium or fast rates of MD loss remained constant. Median rate of MD loss in older (>70 years) eyes was faster than that observed in younger (<60 years) eyes (-0.21 compared with -0.01 dB/year). Median rate of loss did not vary with severity of MD loss at baseline. Frequency of testing, typically carried out annually, did not vary by age, rate of loss or disease severity.

Conclusions: VFs of eyes treated in the first half of the decade deteriorated more rapidly than those in the second half. Several factors might explain these differences but average effects were small and there was no reduction in the proportion of rapidly progressing eyes over the decade. Older age and, to a lesser extent, worse VF damage at diagnosis are indicators for faster VF loss in clinics, but frequency of VF testing was similar for all patients.

Figure 1

A schematic illustrating the VF series inclusion criteria and method for calculating rates of MD loss (dB/year) for three example eyes detected in 2001 (a), 2003 (b), and 2006 (c). Eyes were excluded for o5 VF examinations or o4 years of follow-up. The first VF in each series was omitted to account for perimetric learning effects. Rate was calculated from linear regression of the baseline VF and the series of exams that fell within a 4-year period after it (white window). So, for example, for series (a) the sixth and seventh recorded VFs fall outside this window and are not used in the calculation. This ensures that all rates are estimated with equivalent precision, allowing for comparisons over time. A minimum of three VFs were required to be in this 4-year window. This rate was then assigned to the date of the baseline exam.

Figure 2

Distribution of MD rate in eyes diagnosed in two periods of the decade. Median, 25th (lower quartile), and 10th percentile are indicated. Curved lines represent a spline fit to the histogram. Note the histogram is censored at +1db/year.

Figure 3

Conditional Density Plot showing the temporal change in the relative proportion of eyes with different rates of VF loss (stable, slow, medium, fast), across the midpoint of the study period. A 3% increase in the proportion of stable progressors was identified in this study with a 2% and 1% reduction identified for the slow and medium progressors, respectively. No change was observed in the fast progressors.

Figure 4

Distribution (spline fit of histogram) of MD rate in eyes grouped by baseline age (top) and baseline severity of VF loss (bottom). Median and 10th percentile values are indicated over the study period.

Figure 5

Pie charts estimating the proportion of eyes receiving annual VF testing by (a) patient age, (b) glaucoma severity, and (c) glaucoma progression rate.