UCLA

Glaucoma is the leading cause of blindness in high-income countries like the United States (US) in adults aged 50 years and older. In the US, glaucoma is known to disproportionately affect racially and ethnically minoritized groups, such as Black, Latinx, and Asian/Pacific Islander individuals. Incisional glaucoma surgery remains a mainstay of treatment for severe or medically-uncontrolled glaucoma. Though studies have supported the longstanding clinical finding that Black patients are at increased risk for incisional glaucoma surgical failure, few studies have explored disparities in incisional glaucoma surgical outcomes within a racially and ethnically diverse and representative sample, or the structural inequities that contribute to these disparities.

The first study of this dissertation constructs a retrospective cohort using data from a 20% representative sample of 2016-2018 US fee-for-service Medicare beneficiaries who received incisional glaucoma surgery (trabeculectomy, tube shunt, or EX-PRESS� shunt) to compare risk of surgical failure (defined as glaucoma surgical reoperation) by patient race and ethnicity. The final analytical sample included a total of 12,366 unique beneficiaries, and during the study period, there was a total of 1,590 incisional glaucoma surgical reoperation events, yielding a cumulative incidence of 12.9%. In this diverse and representative national cohort, Black, Latinx, and Asian/Pacific Islander patients had greater risk of reoperation compared to non-Latinx White beneficiaries. Thus, this representative cohort study of national Medicare beneficiaries elucidated new and persistent racial and ethnic disparities in incisional glaucoma surgical outcomes.

The second study examined racial and ethnic disparities in eye care provider networks by applying network science methods to Medicare claims data and determined whether network characteristics of treating surgeons were associated with risk of incisional glaucoma surgical failure. This study utilized the entire population of 2016 fee-for-service California (CA) Medicare beneficiaries aged 65 and older who received incisional glaucoma surgery. Overall, Asian/Pacific Islander patients were more likely to be treated by surgeons with fewer ties to other providers they had worked with previously and Black and Latinx beneficiaries tended to have treating surgeons who had fewer connections to other eye care providers and belonged to smaller, more isolated network clusters. Altogether, results from this second study point to these racial and ethnic disparities in eye care provider networks as possible manifestations of structural racism plaguing our present-day healthcare systems.

The third study estimated the proportion of the racial and ethnic disparity observed in glaucoma surgical outcomes that can be eliminated by theoretically intervening on socioeconomic status (SES) on a national and statewide scale. Two retrospective cohorts were constructed using: (a) a nationally-representative 20% random sample of 2016-2018 US Medicare fee-for-service beneficiaries and (b) the entire population of 2016-2018 CA fee-for-service Medicare beneficiaries who received incisional glaucoma surgery. The SES mediator was dichotomized to low vs. non-low based on dual-eligibility for Medicaid coverage. Causal mediation analysis was used to estimate the proportion of the disparity eliminated after uniform assignment of SES to non-low for all. Results demonstrated that SES mediates racial and ethnic disparities in glaucoma surgical outcomes, though by varying amounts by individual racial and ethnic group. Furthermore, SES mediation of racial and ethnic disparities in glaucoma surgical outcomes was itself modified by local geographic regions and social contexts.

In conclusion, racial and ethnic disparities in glaucoma surgical outcomes persist and have extended to include a wider set of racially- and ethnically-minoritized groups, including Black, Latinx, and Asian/Pacific Islander populations. These disparities are partially driven by structural inequities in eye care provider networks and significant gaps in wealth. Racial and ethnic disparities are complex; future studies are needed to examine other downstream mediating structural inequities (such as other social determinants of health) that represent modifiable targets to intervene upon to achieve equity in glaucoma outcomes.