Purpose
Large archives of electronic visual field (VF) records can be used to investigate trends in glaucoma diagnosis and management. We examine the hypothesis that the average level of severity of vision loss at the point of glaucoma detection (presentation) has changed over a 15 year period in England.
Methods
Around a 500,000 Humphrey SITA VFs recorded at four regionally different glaucoma clinics in England between 1998 and the end of 2012 were retrospectively examined. To be included, patients were required to have a Humphrey mean deviation (MD) outside 95% normative limits in at least one eye and had at least two visits to the glaucoma clinic. The MD of the worse eye at the first hospital visit was used as an estimate of glaucoma vision loss for a patient at presentation; these were also simply stratified as ‘early’ (better than -6dB), ‘moderate’ (-6 to -12dB), ‘advanced’ (worse than -12dB). Simple linear regression of MD against the date of first visit over the 15 year period was used to estimate changes in the level of vision loss at presentation.
Results
A total of 26,131 patients were included in the analysis. The level of glaucoma vision loss at presentation is getting better over time - estimated to be an average 0.11dB per year over the study period (95% confidence interval: 0.09-0.13 dB per year (P<0.001). For example (see figure 1) the percentage of patients with ‘advanced’ vision loss at presentation (MD worse than -12dB) has changed from 29% (1998 - 2002) to 22% in (2008-2012) (P<0.001).
Conclusions
The average level of severity of vision loss at the point of glaucoma detection is improving over time in England. Nevertheless, given the time period examined it is debatable that these statistically significant differences are large enough to conclude that the health service delivery of this aspect of glaucoma is improving greatly. Large numbers of patients still present at glaucoma clinics with significant vision loss.
Keywords: 758 visual fields