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Incidence of diabetic retinopathy in people with type 2 diabetes mellitus attending the Diabetic Retinopathy Screening Service for Wales: retrospective analysis

BMJ 2012; 344 doi: (Published 22 February 2012) Cite this as: BMJ 2012;344:e874
  1. R L Thomas, research assistant1,
  2. F Dunstan, professor of medical statistics2,
  3. S D Luzio, senior lecturer3,
  4. S Roy Chowdury, clinical research fellow1,
  5. S L Hale, consultant ophthalmologist4,
  6. R V North, professor5,
  7. R L Gibbins, retired general practitioner6,
  8. D R Owens, emeritus professor1
  1. 1Diabetes Research Unit, Centre for Endocrine and Diabetes Sciences, University Hospital of Wales, Cardiff CF14 4XW, UK
  2. 2Department of Primary Care and Public Health, School of Medicine, Cardiff University, Cardiff
  3. 3Diabetes Research Group, Swansea University, Swansea, UK
  4. 4Cardiff and Vale University Health Board, University Hospital of Wales
  5. 5School of Optometry and Vision Sciences, Cardiff University
  6. 6Builth Wells, Powys, UK
  1. Correspondence to: D R Owens owensdr{at}
  • Accepted 5 December 2011


Objectives To determine the incidence of any and referable diabetic retinopathy in people with type 2 diabetes mellitus attending an annual screening service for retinopathy and whose first screening episode indicated no evidence of retinopathy.

Design Retrospective four year analysis.

Setting Screenings at the community based Diabetic Retinopathy Screening Service for Wales, United Kingdom.

Participants 57 199 people with type 2 diabetes mellitus, who were diagnosed at age 30 years or older and who had no evidence of diabetic retinopathy at their first screening event between 2005 and 2009. 49 763 (87%) had at least one further screening event within the study period and were included in the analysis.

Main outcome measures Annual incidence and cumulative incidence after four years of any and referable diabetic retinopathy. Relations between available putative risk factors and the onset and progression of retinopathy.

Results Cumulative incidence of any and referable retinopathy at four years was 360.27 and 11.64 per 1000 people, respectively. From the first to fourth year, the annual incidence of any retinopathy fell from 124.94 to 66.59 per 1000 people, compared with referable retinopathy, which increased slightly from 2.02 to 3.54 per 1000 people. Incidence of referable retinopathy was independently associated with known duration of diabetes, age at diagnosis, and use of insulin treatment. For participants needing insulin treatment with a duration of diabetes of 10 years or more, cumulative incidence of referable retinopathy at one and four years was 9.61 and 30.99 per 1000 people, respectively.

Conclusions Our analysis supports the extension of the screening interval for people with type 2 diabetes mellitus beyond the currently recommended 12 months, with the possible exception of those with diabetes duration of 10 years or more and on insulin treatment.


  • We thank the staff at the Diabetic Retinopathy Screening Service for Wales for their support and Digital Healthcare for providing the anonymised data base used in this study.

  • Contributors: All authors contributed to the writing of this report. RT processed, analysed, and interpreted the data. FD provided statistical advice and analysed the data. DO, SL, and RG contributed to the conception, study design, interpretation of the data, and writing of the report. SRC contributed to processing and interpreting the data and SH and RN provided expert advice. All authors approved the final version of this manuscript and DO is also the guarantor for this manuscript.

  • Funding: This study was funded by the Welsh Office of Research and Development and by an unrestricted educational grant from Takeda UK. Takeda UK were not sponsors of the research and were not involved in its design, conduct, or reporting of its findings.

  • Competing interests: All authors have completed the Unified Competing Interest form at (available on request from the corresponding author) and declare: this study was funded by the Welsh Office of Research and Development and by an unrestricted educational grant from Takeda UK; no financial relationships with any organisations that might have an interest in the submitted work in the previous 3 years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: Ethical approval was sought but not required for this study because the ethics committee considered it to be a service evaluation.

  • Data sharing: No additional data available

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