Methodological quality of the review: Low confidence
Author: Bergerhoff K, Clar C, Richter B.
Region: Details not provided
Sector: Diabetes mellitus, diabetic retinopathy (DR)
Sub-sector: Aspirin, treatment, antiplatelet agents
Equity focus: None specified
Review type: Effectiveness review
Quantitative synthesis method: Narrative analysis
Qualitative synthesis methods: Not applicable
Diabetes mellitus is a risk factor for eye disease that can lead to blindness. There have been concerns that aspirin use might be beneficial in treating it. Many studies show that aspirin is not contraindicated in people with retinopathy when used to prevent macrovascular diseases such as myocardial infarction or stroke. Only a few randomized controlled trials (RCTs) have suggested that aspirin reduces microaneurysm formation in early retinopathy. In more severe retinopathy, aspirin did not prevent the development of high-risk retinopathy.
To investigate ‘whether there are beneficial effects of aspirin alone and in combination with other antiplatelet agents in the treatment of diabetic retinopathy, and the relative hazards for the development of high-risk proliferative retinopathy following aspirin treatment.’
A total of three RCTs were included in the review, which examined diabetic patients with (non) proliferative diabetic retinopathy (DR) and aspirin treatment alone or in combination with dipyramidole versus placebo administration.
‘All trials showed that aspirin alone or in combination neither prevented the development of high-risk proliferative retinopathy nor increased the risk of vitreous haemorrhage.’
Authors concluded that: ‘The results suggest that there are no ocular contraindications to taking aspirin if required as part of a treatment for cardiovascular diseases or other medical indications.’
Authors included RCTs that had a control group and studied the efficacy of aspirin therapy alone or in combination with other antiplatelet agents in patients with diabetes with or without non-proliferative or proliferative retinopathy and measured the development or progression of retinopathy. Authors were mainly interested in the comparison of aspirin alone versus placebo or aspirin plus dipyridamole versus placebo. The main outcome measure considered were progression of DR, mortality, and quality of life.
Authors searched the following electronic databases: the Cochrane Library (Issue 3, 2001), including the Cochrane Controlled Trials Register, and MEDLINE (Ovid 1966 to 11, 2001). It was not stated if any language restrictions were applied.
Two independent reviewers judged trial eligibility, collected details of the study population, interventions, and outcomes using a standard data extraction form; and one reviewer assessed the quality of trial reporting. Authors used the quality criteria specified by Schulz et al and Jadad et al to guide the evaluation of each included study. The evaluation included an assessment of randomization, allocation concealment, blinding, description of withdrawals and dropouts, and intention-to-treat analysis. Based on these criteria, studies were categorized as follows: A, B and C. Overall, studies were of good quality (A or B).
Authors decided against conducting a meta-analysis because the studies reported outcome measures in different ways that could not be converted easily into a standard measure. Therefore, authors conducted a systematic review.
Authors did not discuss the applicability/external validity of the review.
Authors did not report the geographical location of included studies, however they did not restrict their search to any particular income setting.
A low confidence was attributed in the conclusions about the effects of this study as major limitations were identified. Authors used appropriate methods to reduce risk of bias in terms of study selection, data extraction and analysis. However, the search strategy was not sufficiently comprehensive that we could be confident that relevant studies were not omitted in the review, which may have potentially affected the overall conclusion of the study.