Vitamin C and superoxide dismutase (SOD) for diabetic retinopathy

Diabetic retinopathy or eye disease is the leading cause of blindness in developed countries. Laser therapy currently is the primary means in the treatment of diabetic retinopathy. It nevertheless is a procedure which destroys important cells in the eye. There are theories that so-called free radicals (substances which are thought to be harmful to body tissues) might be influenced by new medications to prevent or slow down vision loss in people with diabetes. Preliminary studies with vitamin C and 'superoxide dismutase' suggest that they may have an important role in treatment of diabetic retinopathy.
Unfortunately, our thorough search to detect sound clinical studies with these compounds did not identify any relevant trial. Future updates of this review may find important new information about this potentially hopeful new therapy.

Authors' conclusions: 

No research to date has adequately examined the treatment of diabetic retinopathy with vitamin C or SOD in such a way as to indicate whether this form of intervention has a significant impact on the progress of this clinical condition. The potential role of these substances in the treatment of diabetic retinopathy remains open to debate, and it is suggested that future research focusing on patient-oriented outcomes should address this important issue.

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Background: 

There is increasing evidence that diabetic retinopathy is caused by the action of free radicals. Radical scavengers like vitamin C and superoxide dismutase (SOD) may influence the outcome and progression of diabetic retinopathy, but no systematic review of the literature has been published to examine this hypothesis.

Objectives: 

The aim of the current research was to review the literature in a standard systematic way in order to assess the effects of vitamin C and superoxide dismutase on diabetic retinopathy in methodologically robust trials.

Search strategy: 

We tried to obtain studies from computerised searches of MEDLINE, EMBASE, CINAHL, Web of Science and The Cochrane Library.

Selection criteria: 

Only randomized clinical trials (RCTs) that evaluated the effect of vitamin C, superoxide dismutase or both in the treatment of diabetic retinopathy were considered.

Data collection and analysis: 

Two authors independently read all abstracts, titles or both and wanted to assess risk of bias and to perform data extraction. Discrepancies were planned to be resolved by consensus or by the judgement of a third author.

Main results: 

A total of 241 publications were identified by the electronic searches. Of these, 28 were identified as potentially containing information about the treatment of patients with diabetic retinopathy using vitamin C or SOD and were read in full. No trial evaluated the treatment of diabetic retinopathy with vitamin C or SOD.

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