Intravitreal dexamethasone versus bevacizumab in Aboriginal and Torres Strait Islander patients with diabetic macular oedema: The OASIS study (a randomised control trial)

Background: Frequent intravitreal anti-VEGF injections are impractical for many Aboriginal patients with diabetic macular oedema (DMO). The longer acting intravitreal dexamethasone implant (DEX-implant) is approved for DMO but has not been assessed in an Aboriginal population. Methods: This was a prospective, multicentre, randomised, single-masked, non-inferiority clinical trial. Aboriginal adults from Western Australia with DMO were randomised to receive 3-monthly DEX-implant, or monthly intravitreal bevacizumab. The primary outcome was the change in best corrected visual acuity (BCVA) at 12 months. Results: The final endpoint was analysed for 24 DEX-implant and 28 bevacizumab injection eyes. Mean BCVA improved by 4.0 letters (−0.08 LogMAR) in the DEX-implant group and worsened by 5.5 letters (0.11 LogMAR) in the bevacizumab group. Before adjusting for cataract surgery, the upper bound of the two-sided 90% CI for the DEX-implant was 3.5 letters (0.07 LogMAR), which met non-inferiority criteria. The BCVA of remote participants who received the DEX-implant improved by 5.5 letters (0.11 LogMAR), compared to an 18.5 letter (0.37 LogMAR) decline for bevacizumab (p = 0.04). The incidence of steroid-induced ocular hypertension for the DEX-implant was 33.3%. Conclusions: Before adjusting for the effect of cataract surgery, the DEX-implant was non-inferior to bevacizumab for treating DMO in Aboriginal participants. In remote participants, the DEX-implant surpassed non-inferiority to achieve superior outcomes to bevacizumab. The incidence of steroid-induced hypertension was comparable to that reported in non-Aboriginal populations. We provide guidelines for the judicious use of DEX-implant among Aboriginal people, and a framework for performing ophthalmic clinical trials in Aboriginal communities.