The Unfinished Story: Analyzing Publication Rates in Diabetic Retinopathy and Diabetic Macular Edema Trials Before the COVID-19 Era (1972-2018).

Clinical trials are essential to evidence-based ophthalmology, yet publication bias and discontinued studies threaten data transparency. For diabetic retinopathy (DR) and diabetic macular edema (DME), the extent of unpublished or terminated trials remains unclear. This study evaluates publication trends in DR and DME trials conducted prior to the COVID-19 pandemic. We performed a retrospective cross-sectional analysis of interventional DR and DME trials registered in ClinicalTrials.gov from 1972-2018. Collected variables included funding source, intervention type, trial phase, publication and discontinuation status, and sample size. Chi-square tests assessed associations between trial characteristics and publication outcomes using Stata/SE 18.0. Among 333 included trials, 284 were non-terminated. Of these, 70.1% (n=199) were unpublished, representing 26,251 participants, while 29.9% (n=85) were published, accounting for 45,747 participants. Trials with fewer than 50 participants were over three times more likely to remain unpublished (P <0.0001). Industry-funded trials comprised 48.6% of the cohort but were not significantly more likely to publish than academic-funded trials (P = 0.874). Phase 2 trials were the most common (31.2%), and 18.3% of trials lacked phase designation. This is the first study to comprehensively assess publication patterns in DR and DME trials. The high rate of non-publication, particularly among smaller trials, contributes to a substantial loss of participant data and raises ethical concerns. Greater accountability and complete dissemination of trial outcomes are necessary to uphold the integrity of ophthalmic research and ensure that patient contributions meaningfully inform clinical care.