Feature, Report

Using Medicare to detect glaucoma

An additional 79,000 Australians are expected to develop glaucoma in the next five years, costing the economy $4.3 billion [1]. Specsavers optometry director DR BENJAMIN ASHBY explains some of the strategic initiatives, including OCT and visual fields, in place to mitigate this problem.

Despite progress in the understanding of glaucoma pathophysiology, clinical technology, and optometrists’ training and scope as primary eyecare providers, 50% of Australians with glaucoma remain undiagnosed. This is often despite the fact many who likely have the disease have recently accessed eyecare. Ultimately, the undiagnosed glaucoma rate has remained relatively unchanged for the past three decades [2,3,4].

Ben Ashby.

This is primarily due to the nature of glaucoma, with a lack of overt signs and symptoms in early stages and with functional deficits often preceded by extensive structural damage before they manifest in a way patients can notice [5].

According to Dr Benjamin Ashby, optometry director at Specsavers Australia and New Zealand, early detection of glaucoma is critical to preserving vision and maintaining quality of life for patients, as well as providing a more cost-effective method to lessen the burden of the disease on the economy.

As a part of its Transforming Eye Health strategy, Specsavers has collaborated with industry stakeholders to implement several initiatives within its practices to detect and refer those with undiagnosed glaucoma.

Following extensive investigation and piloting, Specsavers invested more than $40 million to rollout optical coherence tomography (OCT) and related training across its network from 2017. The approach was deliberately to use OCT as part of a standard eye test for all patients, harnessing the clinical benefits of this imaging technology to enhance detection of asymptomatic and early stage eye disease.

“OCT has been regarded as a supplementary test for glaucoma diagnosis by optometrists rather than a case-finding tool. Its systematic use on all patients has resulted in an increase in glaucoma detection across our population,” Ashby says.

According to Specsavers, consistent application of OCT as part of the optometric consultation, together with Optometry Benchmark Reporting, clinician education and adherence to the RANZCO Referral Pathways, has been effective in increasing the rate of glaucoma detection in line with published prevalence rates for the condition. The graph in Figure 1 below shows glaucoma detection rates as measured in 2019.

Figure 1 – Glaucoma detection rates by age group from 2019 showing the impact of OCT.

Visual fields to detect glaucoma 

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, Ashby says.

The enhanced visibility of the retinal architecture OCT enables has been beneficial in supporting optometrists to detect early nerve fibre layer and ganglion cell loss. Equipped with this information, Ashby says the data shows optometrists have been better able to make consistent decisions to perform clinically indicated visual field assessment, interpret structural and functional correlations and then refer for ophthalmological intervention appropriately.

“From the outset we have closely monitored the rate of visual field performance before and after introduction of OCT. 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. We measure visual field rates at a national level all the way down to the individual optometrist in any one of our practices,” he says.

In addition to this, Ashby says it has been important to understand the link between visual field performance and detection of glaucoma.

“We first analysed the correlation between visual field performance and glaucoma detection in 2017 using a dataset of 5.3 million patient outcomes. At this time, we found the 13% visual field rate correlated with detection of glaucoma at the population prevalence (see Figure 2 below).

Figure 2 – Data from more than 1,400 optometrists reveals a strong correlation between visual fields and glaucoma referrals.

“Given the scale of the dataset and the gravity of what we had found, we made the decision 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 optometric practice. Since then, we have repeated the analysis and the benchmark continues to be supported by the data.”

From an optometrist’s perspective, this means that if they are 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.

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.

Ashby says 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.

“Medicare funding of visual fields is an important public health lever to support detection and management of glaucoma in the community. It is vital that this government funding is used wisely to provide accessible clinical services that have a measurable impact on detection rates and effective co- management of this endemic cause of avoidable blindness.

“Increasing rates of visual fields across optometry can only be seen in a positive light when it is linked to progress in detecting the 50% of undiagnosed glaucoma in this country. The real concern right now are the thousands of people at risk of glaucoma that have not had access to this service because of COVID-19.”

False positives 

Adaptions in the eye test process have led to increases in detection and referral rates for glaucoma, and a significant increase from 0.55% of patients referred for glaucoma in 2017, compared with 1.26% in 2019. Ashby says this understandably raises questions about false positive referrals.

“We have sought to confirm the appropriateness of glaucoma referrals and worked with e-referral platform Oculo and ophthalmologists across Australia to identify the rate of false positives following specialist assessment,” he says.

A process has been established whereby optometrists are required to classify referral types into one of three categories: ‘new assessment’ for patients who are newly diagnosed by the optometrist and have never been seen by an ophthalmologist; ‘suspect review’ for existing probable glaucoma suspects who are being monitored for progression but have not yet started treatment; and ‘glaucoma review’ for patients with existing confirmed glaucoma.

Ophthalmologists can provide one of three diagnoses after the patient’s attendance through Oculo: ‘glaucoma’, ‘glaucoma suspect’ for patients in whom glaucoma was probable but not confirmed, or ‘no glaucoma’. The percentage of patients who received a diagnosis of ‘no glaucoma’ is used to determine the false positive rate. Ashby says Specsavers has now received feedback on a subset of 784 Australian patient referrals. Of the patient referrals for newly detected glaucoma, 79% were confirmed to have definite or probable glaucoma (see Figure 3 below).

Figure 3 – Ophthalmology feedback on new glaucoma referrals.

Glaucoma surgeon and neuro-ophthalmologist Associate Professor Mitchell Lawlor from Sydney Eye Surgeons and Macquarie Street Eye Surgeons, has contributed to the emerging feedback data.

“The process of capturing and reporting on ophthalmological feedback is crucial in verifying the increasing glaucoma detection rate. Feedback on appropriateness of referrals is key to driving systematic change that ensures the right people are referred at the right time for early treatment of glaucoma,” he says.

Ashby says while the ongoing importance of collecting feedback data is acknowledged, this initial set of outcomes compare favourably to prior studies of optometric glaucoma referrals where up to 58.3% [6, 7] resulted in a ‘no glaucoma’ diagnosis at the first specialist visit.

“This suggests that our systematic use of OCT has lifted detection rates of glaucoma whilst maintaining comparably high levels of referral accuracy and appropriateness.”

More reading

New Specsavers website shares eye health data insights

Expansion plans for Specsavers store network

Prominent Specsavers figure returns to Australia

References

[1] Dirani M, Crowston JG, Taylor PS, et al. Economic impact of primary open-angle glaucoma in Australia. Clin Exp Ophthalmol. 2011;39(7):623-632. doi:10.1111/j.1442-9071.2011.02530.x

[2] Mitchell P, Smith W, Attebo K, Healey PR. Prevalence of open-angle glaucoma in Australia: The blue mountains eye study. Ophthalmology. 1996;103(10):1661-1669. doi:10.1016/S0161-6420(96)30449-1

[3] Keel S, Xie J, Foreman J, et al. Prevalence of glaucoma in the Australian National Eye Health Survey. Br J Ophthalmol. 2019;103(2):191-195. doi:10.1136/bjophthalmol-2017-311786

[4] Sommer A, Tielsch JM, Katz J, et al. Relationship Between Intraocular Pressure and Primary Open Angle Glaucoma Among White and Black Americans: The Baltimore Eye Survey. Arch Ophthalmol. 1991;109(8):1090-1095. doi:10.1001/archopht.1991.01080080050026

[5] Weinreb RN, Aung T, Medeiros FA. The pathophysiology and treatment of glaucoma: A review. JAMA – J Am Med Assoc. 2014;311(18):1901-1911. doi:10.1001/jama.2014.3192

[6] Ratnarajan G, Newsom W, Vernon SA, et al. The effectiveness of schemes that refine referrals between primary and secondary care – The UK experience with glaucoma referrals: The Health Innovation & Education Cluster (HIEC) Glaucoma Pathways Project. BMJ Open. 2013;3(7):1-8. doi:10.1136/bmjopen-2013-002715

[7] Lockwood AJ, Kirwan JF, Ashleigh Z. Optometrists referrals for glaucoma assessment: A prospective survey of clinical data and outcomes. Eye. 2010;24(9):1515-1519. doi:10.1038/eye.2010.77