Comparison of diabetic retinopathy phenotype between Latinos and Blacks☆
Introduction
Diabetic retinopathy (DR), the primary ophthalmic complication of diabetes, is a retinal disorder characterized by signs of increased retinal capillary permeability and ischemia (Kempen et al., 2004). It is estimated that 12,000–24,000 diabetic patients lose sight each year due to DR, making it the leading cause of blindness in adults aged 20–74 years (American Diabetes Association Diabetes Statistics, 2002). DR occurs most often in individuals with long-standing diabetes, and it can be prevented and delayed with aggressive control of blood glucose and blood pressure (Jain, Sarraf, & Fong, 2003).
Latinos and Blacks have a disproportionately higher number of individuals with diabetes (Baker, 2003, West et al., 2001). Of all non-Hispanic Blacks aged ≥20 years, 3.2 million (13.3%) have diabetes and are 1.8 times more likely to have diabetes than non-Hispanic Whites. Mexican-Americans, the largest Hispanic/Latino subgroup in the United States, are 1.7 times more likely to have diabetes than non-Hispanic Whites (American Diabetes Association Diabetes Statistics, 2005).
Several studies have concluded that Latinos and Blacks are at increased risk for developing complications of diabetes such as DR (Harris et al., 1999, Harris et al., 1998). The prevalence of any DR lesion in people already diagnosed with diabetes is 46% higher in African-Americans and 84% higher in Mexican-Americans compared to that in Whites (Harris et al., 1998). Some studies have noted differences in the features of DR between Latinos and Blacks. For example, in a comparison between the Los Angeles Latino Eye Study and the Barbados Eye Study, the ratio of hard exudates to soft exudates in Latinos was 1:1 versus 2:1 in persons of African-Caribbean descent, suggesting that DR in Latinos and Blacks can present differently (Varma, Torres, Pena, Klein, & Azen, 2004). These findings have broad implications for DR prognosis and management.
The Early Treatment of Diabetic Retinopathy Study (ETDRS) and the Diabetic Retinopathy Study (DRS) are the gold standard studies that developed a grading system for assessing features associated with progressive DR using fundus photography (FP) and fluorescein angiography (FA) (Early Treatment Diabetic Retinopathy Study Research Group, 1991a, The Diabetic Retinopathy Study Research Group, 1976). Their patient population was primarily Caucasian, and, therefore, their conclusions may not strictly apply to Black and Latino diabetic patients (Early Treatment Diabetic Retinopathy Study Research Group, 1991b). In this study, FP and FA were systematically graded from a sample population of Black and Latino diabetic patients with DR in an effort to undercover any racial differences in funduscopic and/or angiographic features associated with poor visual and anatomic outcome.
Section snippets
Research design and methods
This was a retrospective study of medical charts from the Eye Clinic at the King–Drew Medical Center (KDMC) in Los Angeles from January 1, 1998, to March 31, 2005. Included patients were self-identified African-Americans, Blacks, Mexican-Americans, Latinos, or Hispanics. These patients were aged ≥15 years, with either documented type 1 or documented type 2 diabetes mellitus and available fundus photographs and fluorescein angiograms.
Patients were excluded if they had poor-quality or incomplete
Results
The study included 367 eyes of 203 patients. Among the patients, 79.8% (n=162) were Latino and 20.1% (n=41) were Black. Gender, age, median ACR, and average HbA1c values were not significantly different between groups (P=.724, .453, and .769, respectively). Both groups had poor glycemic control: the average HbA1c of Latinos was 9.88% and that of Blacks was 9.75% (Table 1).
The overall distributions of the DR grade were similar in both groups (Table 2). The overall presence of CSME was very high
Discussion
It has been well established that there are important racial and ethnic differences in disease prevalence, manifestations, and efficacy of treatment. For example, there are notable ethnic differences in the etiology of blindness in American adults. Glaucoma is the most common cause of blindness in Blacks, whereas age-related macular degeneration (AMD) predominates in Caucasians (Congdon et al., 2004).
AMD is more severe and prevalent in Whites than in Blacks (Friedman, Katz, Bressler, Rahmani, &
Limitations
This was a retrospective chart review with inherent limitations. We were unable to control for other variables such as duration of diabetes, patient medications, and presence of other systemic diseases. A large number of eyes were excluded because of poor-quality imaging or incomplete data. Ascertainment bias in the selection of the patients has already been discussed and may explain the high proportion of CSME and PDR.
The percentage of patients in each ethnic group was representative of the
Acknowledgments
This study was partly supported by an RPB grant to David Sarraf, MD.
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The abstract has been previously published in The Association for Research and Vision in Ophthalmology 2007 Annual Meeting Abstract Search.