According to the latest report of the Vision Loss Expert Group of the Global Burden of Disease Study, the crude prevalence (all ages) of visual impairment and blindness caused by diabetic retinopathy (DR) increased significantly between 1990 and 2015.1 The number of people affected by blindness due to DR increased from 0.2 million to 0.4 million, and moderate to severe vision impairment increased from 1.4 million to 2.6 million.
An increase in age-standardised prevalence of blindness and visual impairment caused by DR was observed in the high income sub-regions—North Africa and the Middle East—whereas the prevalence of blindness and visual impairment due to DR has decreased in all regions of sub-Saharan Africa, Latin America, Oceania, Caribbean, central and eastern Europe.1
DR is the leading cause of preventable blindness in working-age adults. The potential risk of blindness in an individual with diabetes is 2.4 times higher than that of an individual without diabetes.2,3 In 2013, 382 million people had diabetes and this number is expected to rise to 592 million by 2035.4
Systematic screening of diabetic patients has the potential to reduce the incidence of sight-threatening visual impairment. Such programmes have been successfully implemented in many countries. Here, we review the results of the latest studies of DR in Europe and worldwide, which together included at least 10,000 participants.
The Diabetic Retinopathy Screening Service for Lisbon and Tagus Valley—RETINODIAB—was commissioned and carried out in Portugal between July 2009 and October 2014.5 Data analysis included 52,739 patients with type 2 diabetes, diagnosed over the age of 40 years, 49.6% of whom were women.
The mean age of participants was 69.13 years (standard deviation [SD] 11.13) and the mean duration of diabetes was 8.5 years (SD 7.89). DR was detected in a total of 8,584 patients (16.3%). Of these, 5,484 patients (10.4%) had mild non-proliferative DR (NPDR), 1,457 (2.8%) had moderate NPDR, 672 (1.3%) had severe NPDR and 971 (1.8%) had proliferative DR.
Statistical analysis revealed that the presence of any DR, non-referable DR or referable DR was strongly associated with increasing duration of diabetes and earlier age at diagnosis.5
In the United Kingdom, the Clinical Practice Research Datalink (CPRD) electronic health database was used to examine trends in the prevalence and relative risk of retinopathy by diabetes type, patient age, sex, ethnicity, socioeconomic deprivation and region.6 Data were analysed from 7,707,475 patients aged over 12 years from 601 general practices across the UK that contributed to the CRPD from 2004 to 2014.
Of these patients, 338,390 with type 2 diabetes and 30,657 with type 1 diabetes were identified. The prevalence of DR was 48.4% (14,846) in the population with type 1 diabetes mellitus and 28.3% (95,807) in the population with type 2 diabetes mellitus.
Statistical analysis revealed that relative risk of DR in patients with type 2 diabetes mellitus varied significantly with region and was increased for older age groups and in men compared with women, with the risk of severe DR increased in South Asian ethnic groups and more deprived groups. Relative risk of DR for patients with type 1 diabetes mellitus varied with age and region, but not by sex, ethnic group or socioeconomic status.6
Germany and Austria
In Germany and Austria, anonymous patient records accumulated from January 2000 to March 2013 within the German/Austrian Diabetes Prospective Documentation Initiative (DPV) were analysed.7 Complete data were available for 64,784 patients with type 2 diabetes from 166 recruiting centres in Germany and Austria.
Men represented 51.4% of the study population and the mean duration of diabetes was 9.2 years (standard error 0.03). The study showed that retinopathy was absent in 79.88% of patients (51,750) at the most recent visit; 10.26% (6,646) had mild to moderate retinopathy and 9.09% (5,887) had severe non-proliferative or proliferative retinopathy.
Diabetic macular oedema (DMO) was reported in 501 patients (0.77%). Statistical analysis with the Kaplan–Meier method revealed that, after a diabetes duration of 20 years, 38.2% of patients had DR; after 40 years the proportion had increased to 89.7%. The corresponding figures for severe non-proliferative or proliferative retinopathy were 19.7% and 67.5%, and for DMO 1.6% and 9.8%, respectively.7
The Danish Registry of Diabetic Retinopathy (DiaBase) compiles data on all diabetes patients aged ≥18 years who attend screening for diabetic eye disease in hospital eye departments and private ophthalmological practices in Denmark.8 Statistical analysis included data from 77,968 DiaBase patients, collected in 2014–2015.
The prevalence of no DR, NPDR and proliferative DR, respectively, in the study population was 78%, 18% and 4%. However, the overall prevalence of patients in this registry without diabetic maculopathy was 97%.8
In Spain, a population-based prospective study of 15,396 patients with diabetes mellitus was conducted.9 Patients in sixteen Primary Health Care Areas were screened between January 2007 and December 2014.
There were no significant differences in mean age or in age groups between those Health Care Areas and the study sample included more men, which reflects the overall population prevalence of diabetes in Spain.
An increase in the incidence of DR and DMO was observed, especially in the patients aged between 31 and 70 years, and this was linked to bad metabolic control of diabetes mellitus. The incidence of any DR increased from 8.09% in 2007 to 8.99% in 2014, and DMO from 2.00% in 2007 to 2.49% in 2014.9
Dr Michal S. Nowak, PhD
E: [email protected]
Dr Nowak is based at the Provisus Eye Clinic, Czestochowa, Poland. He reports no conflict of interest with the studies mentioned.
Dr Andrzej Grzybowski, PhD
E: [email protected]
Dr Grzybowski is based in the Department of Ophthalmology at the University of Warmia and Mazury, Olsztyn, Poland and the Institute for Research in Ophthalmology, Foundation for Ophthalmology Development, Poznan, Poland. He reports no conflict of interest with the studies mentioned.
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