Our study had several limitations. Repeated in-person eye exams were not possible; thus, we relied on questionnaire and medical record information for disease confirmation, a method that had low sensitivity. However, methodologically, hazard ratios can still be valid if the case definition is highly specific (e.g., reproducible VF loss) and the ascertainment method was unrelated to exposure (we required reports of eye exams at each follow-up cycle).
49 A major limitation was that we had relatively few POAG-affected eyes from those who were black, Asian, or Hispanic white; thus, although some results were statistically significant, our confidence intervals were wide for certain estimates, so the results should be interpreted with ample caution and replicated in another study with a greater number of cases from various races and ethnicities. More broadly, we acknowledge that the NHS, NHS2, and HPFS were cohorts that were not ideally suited for this research question due to the low representation of black, Asian, and Hispanic white populations. Although our study supports the prior work of others that have also reported on racial differences in VF loss development in POAG,
50,51 future studies of VF loss patterns in POAG in much more diverse populations are needed to further substantiate our findings. Furthermore, on all participants, we did not have regularly updated information on IOP information and central corneal thickness. Yet, central corneal thickness is not considered a strong POAG risk factor
52 in the general population, and in the Baltimore Eye Study (and among our cases;
Supplementary Table S2), untreated IOP among cases was similar in prevalent POAG cases among blacks and whites.
15 Also, because our study participants were health professionals, our results may not be generalizable to general populations, where racial/ethnic disparities in POAG may be larger. Finally, although all of our participants were health professionals, there may have been residual confounding by factors that we were not able to adjust for, such as quality of eye exams, early childhood environment, and social treatment, which may have accounted for some of the race / ethnic differences.