OBJECTIVE To examine the global prevalence and major risk factors for diabetic retinopathy (DR) and vision-threatening diabetic retinopathy (VTDR) among people with diabetes. RESEARCH DESIGN AND METHODS A pooled analysis using individual participant data from population-based studies around the world was performed. A systematic literature review was conducted to identify all population-based studies in general populations or individuals with diabetes who had ascertained DR from retinal photographs. Studies provided data for DR end points, including any DR, proliferative DR, diabetic macular edema, and VTDR, and also major systemic risk factors. Pooled prevalence estimates were directly age-standardized to the 2010 World Diabetes Population aged 20–79 years. RESULTS A total of 35 studies (1980–2008) provided data from 22,896 individuals with diabetes. The overall prevalence was 34.6% (95% CI 34.5–34.8) for any DR, 6.96% (6.87–7.04) for proliferative DR, 6.81% (6.74–6.89) for diabetic macular edema, and 10.2% (10.1–10.3) for VTDR. All DR prevalence end points increased with diabetes duration, hemoglobin A_1c, and blood pressure levels and were higher in people with type 1 compared with type 2 diabetes. CONCLUSIONS There are approximately 93 million people with DR, 17 million with proliferative DR, 21 million with diabetic macular edema, and 28 million with VTDR worldwide. Longer diabetes duration and poorer glycemic and blood pressure control are strongly associated with DR. These data highlight the substantial worldwide public health burden of DR and the importance of modifiable risk factors in its occurrence. This study is limited by data pooled from studies at different time points, with different methodologies and population characteristics.

The incidence of diabetes is increasing, but that of diabetic retinopathy is falling, probably owing to better management of glucose levels, lipid abnormalities, and hypertension. Clinical trials of VEGF and PPAR-α inhibitors are improving vision and providing insights into pathogenesis.

Iris Heid, Gonçalo Abecasis, Sudha Iyengar and colleagues report the results of a large genome-wide association meta-analysis of macular degeneration based on over 43,000 subjects. They identify 16 new risk loci, including some very rare coding variants. Advanced age-related macular degeneration (AMD) is the leading cause of blindness in the elderly, with limited therapeutic options. Here we report on a study of >12 million variants, including 163,714 directly genotyped, mostly rare, protein-altering variants. Analyzing 16,144 patients and 17,832 controls, we identify 52 independently associated common and rare variants (P < 5 × 10−8) distributed across 34 loci. Although wet and dry AMD subtypes exhibit predominantly shared genetics, we identify the first genetic association signal specific to wet AMD, near MMP9 (difference P value = 4.1 × 10−10). Very rare coding variants (frequency <0.1%) in CFH, CFI and TIMP3 suggest causal roles for these genes, as does a splice variant in SLC16A8. Our results support the hypothesis that rare coding variants can pinpoint causal genes within known genetic loci and illustrate that applying the approach systematically to detect new loci requires extremely large sample sizes.

Diabetic retinopathy is the leading cause of new cases of legal blindness among adults aged 20 to 74 years in the United States.¹ Vision loss due to diabetic retinopathy occurs through a variety of mechanisms, including retinal detachment, preretinal or vitreous hemorrhage, associated neovascular glaucoma, and macular edema or capillary nonperfusion.² The presence of diabetic retinopathy may indicate microcirculatory dysfunction in other organ systems.^3,4 Diabetes-related blindness is a personal catastrophe to the individual and costs the United States approximately $500 million annually.⁵ However, risk of vision loss due to diabetic retinopathy can be reduced by effective control of serum glucose and blood pressure and by its early detection and timely treatment.^6-8 The efficacy and cost-effectiveness of early detection and treatment of diabetic retinopathy is well established.^9,10

The prevalence of taste and smell disorders in the United States is unknown. More than 200 000 visits are made to physicians each year for chemosensory complaints,¹ yet most chemosensory problems may be undetected. The prevalence of chronic olfactory problems from the National Health Interview Survey (NHIS) was estimated at 1.42%, or 2.7 million Americans. In the age groups of 55 to 64 years, 65 to 74 years, and 75 years or older, the prevalence rates were 1.99%, 2.65%, and 4.60%, respectively.² A National Geographic survey in 1986 estimated prevalence among its readership of 0.8%.³ These data are informative but are based on self-report and may substantially underestimate prevalence.