Geographic and socioeconomic access disparities to Phase 3 clinical trials in ophthalmology in the United States.

BACKGROUND/OBJECTIVE: To identify geographic and socioeconomic variables associated with residential proximity to Phase 3 ophthalmology clinical trial sites. METHODS: The geographic location of clinical trial sites for Phase 3 clinical trials in ophthalmology was identified using ClinicalTrials.gov. Driving time from each United States (US) census tract centroid to nearest clinical trial site was calculated using real traffic patterns. Travel data were crosslinked to census-tract level public datasets from United States Census Bureau American Community Survey (ACS). Cross-sectional multivariable regression was used to identify associations between census-tract sociodemographic factors and driving time (>60 min) from each census tract centroid to the nearest clinical trial site. RESULTS: There were 2330 unique clinical trial sites and 71,897 census tracts. Shortest median time was to retina sites [33.7 min (18.7, 70.1 min)]. Longest median time was to neuro-ophthalmology sites [119.8 min (48.7, 240.4 min)]. Driving >60 min was associated with rural tracts [adjusted odds ratio (aOR) 7.60; 95% CI (5.66-10.20), p < 0.0001]; Midwest [aOR 1.84(1.15-2.96), p = 0.01], South [aOR 2.57 (1.38-4.79), p < 0.01], and West [aOR 2.52 (1.52-4.17), p < 0.001] v. Northeast; and tracts with higher visual impairment [aOR 1.07 (1.03-1.10), p < 0.001)]; higher poverty levels [4th v.1st Quartile of population below poverty, aOR 2.26 (1.72-2.98), p < 0.0001]; and lower education levels [high school v. Bachelor's degree or higher aOR 1.02 (1.00-1.03), p = 0.0072]. CONCLUSIONS: There are significant geographic and socioeconomic disparities in access to ophthalmology clinical trial sites for rural, non-Northeastern, poorer, and lower education level census tracts, and for census tracts with higher levels of self-reported visual impairment.