OCT helps to facilitate the detection of glaucoma at a stage where visual field loss is minimal, allowing the greatest opportunity for patients to maintain vision and quality of life.
The enhanced visibility of the retinal architecture enabled by OCT has been hugely beneficial in supporting optometrists to detect early nerve fibre layer and ganglion cell loss. Equipped with this information, the data shows optometrists have been better able to make consistent patient management decisions to perform clinically indicated visual field assessment, interpret structural and functional correlations and then refer for ophthalmological intervention appropriately.
From the outset, the rate of visual field performance before and after introduction of OCT has been closely monitored. This was, and continues to be, the clearest first indicator of whether the technology is enhancing identification of clinical risk factors for glaucoma and other eye conditions. Visual field rates are measured at a national and optometrist level in all practices.
In addition to this, it has been important to understand the link between visual field performance and detection of glaucoma. In 2017, Specsavers first analysed the correlation between visual field performance and glaucoma detection using a dataset of 5.3 million patient outcomes. At this time, the 13% visual field rate correlated with detection of glaucoma at the population prevalence.
Given the scale of the dataset and the gravity of what was found, a decision was made to benchmark visual field performance as a point of reference, so optometrists could apply this in the context of the RANZCO Referral Pathways for Glaucoma with the aim of enhancing detection of glaucoma in their communities.  This benchmark was a crucial step in drawing attention to the evidence and set a precedent as it was the first ever data-led benchmark derived for visual fields in Specsavers optometric practice. Since then, the analysis has been repeated and the benchmark continues to be supported by the data.
This means that if an optometrist is seeing 15 patients per day, statistically, one or two of them will require visual field testing on that same day and over a week, one or two patients will be referred for specialist follow up.
Figure 1 – relationship between visual fields and glaucoma referrals. Data from over 1400 optometrists reveals a strong correlation between visual fields and glaucoma referrals.
Detection of glaucoma at this rate does rely on optometrists assessing the eye both structurally and functionally, conducting visual field assessments for all patients where clinically indicated.
Specsavers’ visual field monitoring also extends to analysing Medicare utilisation in the context of all eye health providers in Australia. The visual field trends being observed through the Medicare national dataset are reflective of the changes instigated by Specsavers in the past few years and directly correlate with increased glaucoma detection.