Association between diabetic eye disease and other complications of diabetes: Implications for care. A systematic review

Methodological quality of the review:  Low confidence

Author: Pearce I, Simó R, Lövestam-Adrian M, Wong DT, Evans M

Region: Not reported

Sector: Diabetic retinopathy

Sub-sector: Complications

Equity focus:  None specified

Review type: Other review

Quantitative synthesis method: Narrative synthesis

Qualitative synthesis method: Not applicable

Background:

Diabetic retinopathy (DR) is the most common complication of diabetes and remains the leading cause of blindness among working-age individuals in most developed countries. DR has long been considered a microvascular complication of diabetes. However, growing evidence suggests that abnormalities in retinal function can be detected in patients without any evidence of microvascular abnormalities, and the American Diabetes Association defined DR as a highly specific neurovascular complication.

Objectives:

Examine the associations between diabetic retinopathy (DR) and the common micro- and macrovascular complications of diabetes mellitus, and how these could potentially affect clinical practice.

Main findings:

In total authors included 70 studies in the review. Authors found that DR is consistently associated with other complications of diabetes, with the severity of DR linked to a higher risk of the presence of, or of developing, other micro- and macrovascular complications. In particular, authors report that DR increases the likelihood of having or developing nephropathy and is also a strong predictor of stroke and cardiovascular disease, and progression of DR significantly increases this risk. Authors note that proliferative DR is a strong risk factor for peripheral arterial disease, which carries a risk of lower extremity ulceration and amputation. Additionally, authors’ findings suggest that a patient with DR has an overall worse prognosis than a patient without DR. In conclusion, authors note that this analysis highlights the need for a coordinated and collaborative approach to patient management. Given the widespread use of DR screening programmes that can be performed outside of an ophthalmology office, and the overall cost-effectiveness of DR screening, the presence and severity of DR can be a means of identifying patients at increased risk for micro and macrovascular complications, enabling earlier detection, referral and intervention with the aim of reducing morbidity and mortality among patients with diabetes. Healthcare professionals involved in the management of diabetes should encourage regular DR screening.

Methodology: 

Inclusion criteria were: (a) studies involving a population of patients with diabetes, with no restriction on clinical characteristics, glycated haemoglobin [HbA1c] and comorbidity or treatment history, and (b) studies that evaluated the presence or development of DR in conjunction with other vascular complications of diabetes.

A literature search of the PubMed database was performed using a structured approach to identify relevant studies. Only peer reviewed original research studies and reviews were included, and no geographical, date or language restrictions were applied.

Authors screened the studies for relevance against the inclusion exclusion criteria. Extracted information included study design, population characteristics, conclusions and limitations. Precedence was given to studies specifically designed to investigate the relationship between DR and other complications of diabetes, and to studies in which statistical analyses were adjusted for confounding factors.

Applicability/external validity:

Authors note that this study has provided clear evidence supporting relationships between DR and complications of diabetes, including micro- and macrovascular conditions and events. They note that although many of these associations have been identified in cross-sectional and retrospective studies, several have been confirmed in prospective investigations, based on multivariate analyses that controlled for the influence of traditional or other known risk factors.

Geographic focus:

Authors did not report the geographical location of included studies and did not mention the applicability of the results to low- and middle-income settings.

Summary of quality assessment:

Overall, there is low confidence in the conclusions of this study as important limitations were identified. Authors did not conduct a thorough search of the literature to ensure all eligible studies were included, therefore indicating the presence of publication bias within the review. In addition, authors did not report methods used to screen studies for inclusion and methods used to extract data of included studies.