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Three representative studies recently completed by SCEI researchers are presented below.

1. Visual Acuity and Quality of Life

Title: Differences in Vision-Specific Quality of Life with Visual Acuity by Race, Ethnicity in the Multiethnic Ophthalmology Cohorts of California Study (MOCCaS)

Authors: Roberta McKean-Cowdin, Dominic J. Grisafe, Mina Torres, Bruce Burkemper, Kaili Ding, Xuejuan Jiang, Benjamin Xu, Rohit Varma

Purpose: To compare racial, ethnic differences in visual acuity (VA) on vision-specific quality of life (VSQOL).

Methods: In the MOCCaS, the impact of VA on VSQOL measured by the National Eye Institute Visual Function Questionnaire (NEI-VFQ-25) was evaluated in a population-based sample of African American (AA), Chinese American (CA), and Latino (LAT) adults. A total of 17,071 adults ages 40 and older participated in a comprehensive ophthalmologic examination and in-person interviews from 2000 to 2018. Distance VA was measured using a detailed ophthalmologic examination using standard ETDRS protocol at baseline. VSQOL was assessed at the end of the clinical examination using the NEI-VFQ-25. Vision-related daily task (VRDT) and well-being composite scores were calculated using item response theory (IRT); classical test theory (CTT) was used to score 11 subscales with values ranging from 0 to 100, with higher scores representing better visual functioning.

Results: 14,570 participants (5,171 AA, 4,151 CA, and 5,248 LAT) with complete data were included in the analysis. Predicted VRDT and well-being composite scores were significantly lower for Latinos across level of presenting VA compared to AA or CA participants. An inverse relationship was found with significantly lower levels of patient reported ability to complete VRDT after adjustment for covariates using IRT. A 2-line change in VA was associated with a 4.6-point change in VRDT score for LAT participants. 3.9 for CA participants, and 2.9 for AA participants. The difference was greater for those ages 65 and older. No significant differences in change for well-being were identified by race, ethnicity (3.2 LAT, 3.0 CA, and 3.0 AA). Classical test theory revealed significant interactions for driving difficulty with VA, age, and race.

Conclusions: Each 2-line loss in VA has significant impact on patient reported ability to complete VRDT, and the degree of impact varies by race, ethnicity, and age. The functional impact of VA level by race, ethnicity, and age has not been well characterized, and the potential role of health disparity needs further exploration.

2. Glycemic Control and Diabetic Retinopathy in African American Females

Title: Glycemic control and diabetic retinopathy among older African American females with sickle cell trait and G6PD deficiency

Authors: Xuejuan Jiang, Victoria Yu, Roberta McKean-Cowdin, Mina Torres, Rohit Varma

Purpose: Recent evidence suggests that glycated hemoglobin (HbA1c) levels may be systematically underestimating past blood glucose levels among individuals with sickle cell trait (SCT) and those with glucose-6-phosphate dehydrogenase (G6PD) deficiency, leading to an underdiagnosis of diabetes and diabetes control. However, it is unclear how these genotype differences may affect the risk of having diabetic retinopathy (DR). The objective of this study is to evaluate the impact of SCT and G6PD deficiency on HbA1c levels and having DR among a sample of community-dwelling African American females.

Methods: The African American Eye Disease Study (AFEDS) is a population-based, cross-sectional study of 40+ years old African Americans in Los Angeles, CA. HbA1c and random blood glucose measurements were obtained using a DCA 2000 Analyzer and HemoCue B-Glucose System. DR was graded according to ETDRS grading of DR based on photography of 7 standard fields of the fundus of each eye. From 1,789 female participants, genotype DNAs were extracted. Genotype data were obtained for rs334, encoding the sickle cell mutation, and for rs5030868, encoding the G6PD deficiency mutation. Demographic and biological laboratory data including DR severity were compared statistically between those with and without the rs334 and those with and without G6PD deficiency mutation.

Results: Compared with individuals without SCT, individuals with SCT had a higher HbA1c level (6.1 vs. 5.9, P<0.05), despite similar levels of random glucose (P=0.42), and a higher prevalence of diabetes (25.5% vs. 18.2%, P<0.05). The odds of having diabetes in SCT individuals were 1.58 times those of individuals without SCT. The prevalence of DR was lower in SCT individuals (30%) than in non-SCT participants (48%); however, this difference was not statistically significant (P=0.69). For G6PD deficiency, the mean HbA1c level was lower in carriers and deficient individuals than normal individuals (p < 0.001), despite a similar random glucose level (P=0.37). There was no significant difference in the prevalence of diabetes and DR by G6PD genotype (Ps=0.29 and 0.64, respectively).

Conclusions: Among older African American females, SCT is associated with a higher level of HbA1c and higher prevalence of diabetes but a lower prevalence of DR. G6PD deficiency is associated with a lower level of HbA1c but did not appear to affect the prevalence of diabetes and DR. Further studies with larger sample are needed to confirm these findings.

3. Uncorrected Refracted Error in African Americans

Title: The Prevalence and Risk Indicators of Uncorrected Refractive Error in African Americans: The African American Eye Disease Study (AFEDS)

Authors: Nathan Dhablania, Mina Torres, Kaili Ding, Bruce Burkemper, Roberta McKean- Cowdin, Rohit Varma, and the African American Eye Disease Study Group

Purpose: To determine the burden of uncorrected refractive error (UCRE) and the risk factors associated with UCRE in a population-based sample of African American adults.

Methods: A population-based sample of self-identified African Americans 40 years of age and older (n = 6347) from thirty contiguous census tracts in Inglewood, California, underwent a complete ophthalmic examination, and an in-home-administered questionnaire to assess sociodemographic (e.g. marital status, employment status, education level, annual income level), lifestyle (e.g. smoking history), and biological and medical (e.g. weight and height, health and vision insurance, healthcare and eye care utilization) risk factors associated with UCRE. UCRE was defined as a ≥ 2-line improvement with refraction in the better seeing eye. Sex- and age- specific burden of UCRE were calculated and multiple regression analyses were used to identify independent risk factors.

Results: Of the 7957 eligible participants in AFEDS, 6347 (80%) completed both the in-home interview and the clinical examination. The overall prevalence of UCRE was 14.6% (n = 925). There was no significant age or gender trends in burden of UCRE (P > 0.05). Annual household income of less than $20,000 and lack of vision care insurance were significant independent risk indicators for UCRE.

Conclusion: Our data confirms the high burden of UCRE in African Americans making it the leading cause of visual impairment in this population. Provision of vision care and prescription lenses or glasses is an affordable and achievable health care intervention that would reduce the burden of visual impairment in African American adults and help improve vision health in this vulnerable minority population.