It is no secret that too many optometry patients with normal tension glaucoma go undetected. In the Blue Mountains Eye Study, 75% of previously undiagnosed Australian glaucoma patients were reported to have an intraocular pressure of less than 22 mmHg, reinforcing the challenges of detecting normal tension glaucoma.
In 2017, Specsavers started the rollout of OCT across its network as a part of a nationwide strategy to improve glaucoma detection. As previously reported, this resulted in a dramatic rise in detection of glaucoma across the Specsavers network, approaching the approximate prevalence rate of the condition indicated by international studies.
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 more 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.
The Specsavers’ dataset now includes over 115,000 glaucoma referrals issued since 2016 and is enabling significant insight into glaucoma detection in Australia. 75% of the referrals within the dataset can be classified based on intraocular pressure at the time of referral.
As the graph below shows, normal tension glaucoma referrals more than doubled in the period between 2016 and 2018. Specsavers began it’s $40million OCT roll out in October 2017 and two years later, all Specsavers stores were making use of this technology for every patient.
The step-change seen as a result of OCT introduction is evident. The stabilisation of normal tension glaucoma referrals in the past 12 months is in line with previously reported Australian data, and suggests that OCT is a valuable case-finding tool for detecting normal tension glaucoma.
To begin to qualify this, Specsavers’ instated classification of glaucoma referrals in December 2018 whereby optometrists can indicate if the glaucoma referral they are making is for a ‘new detection’, ‘glaucoma suspect’ or ‘existing (glaucoma) diagnosis’. This allows for a closer look at patients who are being diagnosed with glaucoma for the first time.
Of those newly diagnosed with glaucoma since December 2018, 71.1% had intraocular pressures below 22mmHg, in line with published Australian studies (The Australian National Eye Health Survey and the Blue Mountains Eye Study). Interestingly the data indicates that normal tension glaucoma is being detected at a similar rate across all age categories, suggesting that OCT can enhance detection of normal tension glaucoma in all age groups, not just younger patients.
A pivotal measure is of course, the feedback from ophthalmology to confirm validity of these referrals. Emerging feedback data of 442 normal tension glaucoma referrals suggests that the accuracy is equivalent to existing Specsavers’ feedback data for all glaucoma referrals. Currently, the false positive rate for normal tension glaucoma referrals sits at 15%, with 29% of referrals being confirmed as glaucoma suspects and 56% diagnosed with glaucoma (total glaucoma referral false positive rate is 21%).
Glaucoma surgeon and neuro-ophthalmologist A/Prof Mitchell Lawlor from Sydney Eye Surgeons and Macquarie Street Eye Surgeons, has contributed to the emerging feedback data and says, “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.”