A pioneering study out of Western Australia has shown that a longer acting intravitreal dexamethasone implant (DEX-implant) may lead to better outcomes in some Aboriginal patients with diabetic macular oedema (DMO) compared with the standard of care, anti-VEGF injections.
With findings published in the RANZCO journal Clinical and Experimental Ophthalmology last month, the Lions Eye Institute (LEI) OASIS Study has been heralded as a world-first clinical trial in ophthalmology to exclusively recruit Indigenous patients.
Led by Associate Professor Hessom Razavi with co-authors Dr Joos Meyer, Ms Carly Fry and Associate Professor Angus Turner, the research team outlined the impracticality of frequent intravitreal anti-VEGF injections for many Aboriginal patients with DMO, which can require an injection every month, or up to 12 injection appointments per year.
They investigated whether outcomes could be improved by using a longer acting DEX-implant, which involves fewer injections (3-6 months), and is approved for DMO but was yet to be assessed in an Aboriginal population.
The prospective, multicentre, randomised, single-masked, non-inferiority clinical trial recruited 38 Aboriginal patients – involving 52 eyes with DMO – from WA who were randomised to receive a three-monthly DEX-implant (Ozurdex), or monthly intravitreal bevacizumab (Avastin).
The primary outcome was the change in best corrected visual acuity (BCVA) at 12 months.
In an article written for The Conversation, Razavi said the results showed patients who received DEX-implants gained four extra letters on a standard eye chart, equivalent to a 6.2% improvement in their vision from baseline. Those who received the anti-VEGF agent, meanwhile, lost 5.5 letters on average, representing an 8.9% decline.
Taken together, the results represented a 15% (9.5 letter) visual advantage for patients who received DEX-implant.
He said the disparity was most pronounced in country towns, where the DEX-implant had a 37% (24 letter) advantage over the anti-VEGF agent.
In the study, the authors concluded that before adjusting for the effect of cataract surgery, the DEX-implant was non-inferior to bevacizumab for treating DMO in Aboriginal patients.
And in remote participants, the DEX-implant surpassed non-inferiority to achieve superior outcomes to bevacizumab.
Razavi said the DEX-implant’s better performance was related to its less frequent, therefore more practical, dosing regime.
“Over 12 months, patients who were meant to receive four dexamethasone implant injections, received an average of 3.3 injections. This meant that, on average, they received 82.5% of their intended treatments,” he wrote in The Conversation.
“Anti-VEGF patients, meanwhile, received 7.2 of their scheduled 12 injections. This equated to only 60% of their intended treatments, and reflects the difficulty of attending monthly appointments in the real world. Anti-VEGF patients had more than twice as many injections as dexamethasone implant patients, yet ended up with poorer vision.”
Importantly, however, the incidence of steroid-induced ocular hypertension for the DEX-implant was 33.3%, presenting a glaucoma risk, which was comparable to that reported in non-Aboriginal populations. Steroid injections are also known to accelerate cataract formation.
Therefore, the authors provided guidelines for the judicious use of DEX-implant among Aboriginal people.
They also developed a framework for performing ophthalmic clinical trials in Aboriginal communities.
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