Methodological quality of the review: Medium confidence

Author: Mohamed Q, Gillies MC, Wong TY.

Region: Details not provided

Sector: Diabetic retinopathy

Sub-sector: Glycemic control, blood pressure, medical interventions and diabetic macular Oedema.

Equity focus: None specified

Review type: Effectiveness review

Quantitative synthesis method: Narrative analysis

Qualitative synthesis methods: Not applicable

Background

Diabetic Retinopathy (DR) is the leading cause of blindness in the working-age population. Primary interventions, such as intensive glycemic and blood pressure control, can reduce the incidence of DR, while secondary interventions such as laser photocoagulation, may prevent further progression of DR and vision loss. There are many new interventions, but the evidence to support their use is uncertain.

Research objectives

To review the best evidence for primary and secondary intervention in the management of DR, including diabetic macular oedema (DME).

Main findings

The authors included 41 randomized controlled trials (RCTs) and three meta-analysis, evaluating interventions for DR in the review. Studies used different methods to ascertain retinopathy including clinical ophthalmoscopy, retinal photography, and/or fluorescein angiography. It should also be noted that studies also classified DR differently. Authors reported the following results:

Tight glycemic and blood pressure control reduced the incidence and progression of DR. Pan-retinal laser photocoagulation reduced the risk of moderate and severe visual loss by 50% in patients with severe non-proliferative and proliferative retinopathy. Focal laser photocoagulation reduced the risk of moderate visual loss by 50% to 70% in eyes with diabetic macular oedema. Early vitrectomy improved visual recovery in patients with proliferative retinopathy and severe vitreous haemorrhage. Intravitreal injections of steroids might be considered in eyes with persistent loss of vision when conventional treatment had failed. There was insufficient evidence for the efficacy or safety of lipid-lowering therapy, medical interventions, or anti-vascular endothelial growth factors on the incidence or progression of DR.

Authors concluded that tight glycemic and blood pressure control remained the cornerstone in the primary prevention of DR. Panretinal and focal retinal laser photocoagulation reduced the risk of visual loss in patients with severe DR and macular oedema, respectively. There was insufficient evidence at the time to recommend routine use of other treatments. They also noted that there was weak evidence that vitrectomy might be beneficial in some patients with macular oedema but well-conducted studies with longer follow-up were needed.

Methodology

Authors included RCTs or meta-analyses evaluating interventions for DR including 12 or more months of follow-up. Studies written in languages other than English were not considered for inclusion. For primary interventions, outcome measures included incidence of new DR and rate adverse effects of interventions. For secondary interventions, outcome measures included progression of DR, changes in visual acuity and macular thickness, and rates of legal blindness and adverse effects. For some RCTs, both primary (incidence of DR) and secondary interventions (progression of DR) were evaluated. Authors used Delphi consensus criteria list to select well-conducted studies.

Articles were retrieved using MEDLINE (1966 to May 2007), EMBASE, Cochrane Collaborations, the Association for Research in Vision and Ophthalmology database, and the National Institutes of Health Clinical Trials Database until May 2007. Search terms included variations of keywords for retinopathy, diabetes, DR, DME, retinal neovascularization, controlled clinical trial, and randomized controlled trial. This was supplemented by hand searching the reference lists of major review articles.

Studies were evaluated on a standardized data extraction form for: (1) valid method of randomization; (2) concealed allocation of treatment; (3) similarity of groups at baseline regarding the most important prognostic indicators; (4) clearly specified eligibility criteria; (5) masking of outcome assessor; (6) masking of care provider; (7) masking of patient; (8) reporting of point estimates and measures of variability for outcomes; (9) intention-to-treat analysis; and (10) acceptable  loss to follow-up rate unlikely to cause bias. Studies were scored out of a maximum of 10, and studies with a score greater than five were considered higher-quality studies. For each intervention, authors graded the overall strength of evidence as levels I, II, or III and the ratings for clinical recommendations as levels A, B, and C, using previously reported criteria.

Authors conducted a systematic review of the literature gathered to determine the best evidence for primary and secondary interventions for DR.

Applicability/external validity

The generalizability/applicability/external validity of the results was not discussed within the review.

Geographic focus

Geographical location of studies included was not provided in the review.

Quality assessment

Authors conducted a thorough search of the literature to ensure that that the best evidence for primary and secondary interventions for DR were included in the review. To ensure the best evidence was included authors used Delphi consensus criteria list; and appropriate criteria was used to assess included studies.

It was not clear whether if selection bias was avoided as well as if the characteristics and results of the included studies were reliably reported, as reviewers did not report if screening of articles for inclusion and data extraction was conducted by two reviewers independently. Therefore, this review was awarded medium confidence in the conclusions about the effects of this study.