Microbial Keratitis Severity Worsened With Neighborhood, Patient Factors

Microbial keratitis severity can be worse for patients who live in areas with increased segregation, lower access to personal transportation, and worse Area Deprivation Index (ADI) scores, according to a study published in JAMA Ophthalmology. Ophthalmologists may consider these neighborhood-level factors when assessing presenting visual acuity in patients with microbial keratitis.

Researchers conducted a cross-sectional study to establish the connection between social risk factors and microbial keratitis severity as measured by presenting best-corrected visual acuity (BCVA). They evaluated records from 2990 patients with microbial keratitis (mean [SD] age, 48.6 [21.3] years; 57.6% women) who presented to the University of Michigan with microbial keratitis between 2012 and 2021.

The researchers obtained individual-level characteristics (age, self-reported sex, self-reported race and ethnicity), presenting logarithm of the minimum angle of resolution (logMAR), and microbial keratitis severity as it related to BCVA. They also established neighborhood-level factors, which include measures of inequity, housing burden, and transportation at the census block group.

The review included an analysis of participants’ ADI, a national percentile ranking that factors in neighborhood socioeconomic disadvantage via composite measures combining income, employment, housing quality, socioeconomic status, and education. The ADI ranges from 1% to 100%, with higher percentiles indicating worse deprivation.

Using 2-sample t, Wilcoxon, and χ2 tests, they also assessed univariate associations of presenting BCVA (<20/40 vs ≥20/40) with individual-level characteristics. They used logistic regression to test associations of neighborhood-level characteristics with the probability of presenting BCVA worse than 20/40 after adjustment for patient demographics.

The participants of this study self-identified as Asian (4.5%), Black (7.8%), Hispanic (3.5%), non-Hispanic (96.5%), White (84.4%), and other (3.3%; included any race not previously listed). Median presenting BCVA was 0.40 logMAR units, and 1508 of 2798 patients (53.9%) presented with BCVA worse than 20/40, indicating greater microbial keratitis severity.

Participants of this study who presented with BCVA of 20/40 or worse were more often older (56.0 [20.8] years) compared with those who presented with a BCVA of 20/40 logMAR or better (41.3 [18.0] years; P <.001). Men were more likely to have worse microbial keratitis severity compared with women (P =.04).

Additionally, patients with Black (difference, 25.7%; 95% CI, 15.0-36.5%; P <.001) or White (difference, 22.6%; 95% CI, 13.9%-31.3%; P <.001) ethnicities were more likely to present with BCVA worse than 20/40 compared with those who had Asian or Hispanic ethnicities (difference, 14.6%; 95% CI, 4.5%-24.8%; P =.04).

And while age and race play a significant role, where a patient lives can also factor into microbial keratitis severity and visual acuity at first presentation. Neighborhood-level risk factors include ADI scores, which were worse for participants who presented with a BCVA worse than 20/40 logMAR than those with BCVA better than 20/40 logMAR (mean [SD] ADI, 54.2 [24.7] vs 40.4 [25.6], respectively; difference=13.8; 95% CI, 11.9-15.8; Holm-adjusted P <.001).

Patients with worse microbial keratitis severity also lived in areas with larger percentages of households with no car (mean of 6.1% [8.5%] vs 5.0% [7.6%], respectively; difference=1.1%; 95% CI, 0.5%-1.7%; Holm-adjusted P <.001) and a lower average number of cars per household (mean, 1.83 [0.39] vs 1.88 [0.39], respectively; difference=-0.05; 95% CI, -0.08 to -0.01; Holm-adjusted P =.04) compared with participants who had BCVAs better than 20/40 logMAR.

Racial segregation, as measured by the Theil H Index, also appears to be associated with microbial keratitis severity worse than BCVA 20/40 (mean Theil H index, 0.20 [0.10] vs 0.17 [0.08], respectively; difference=0.03; 95% CI, 0.02-0.04; Holm-adjusted P <.001).

Even after adjusting for previously identified individual risk characteristics, patients had higher microbial keratitis severity in neighborhoods associated with these risk factors.

“Addressing the underlying inequities and repairing neighborhood infrastructure may improve eye health outcomes,” according to the researchers.

Study limitations include a misalignment between patient data and neighborhood-level data and the fact that study findings may not generalize to populations outside the study sample.