Evidence for the use of nutritional supplements and herbal medicines in common eye diseases

Methodological quality of the review: Low confidence

Author: West LA, Oren AG, Moroi SE.

Region: Worldwide

Sector: Cataract, age-related macular degeneration (AMD), glaucoma and diabetic retinopathy

Sub-sector: Preventing/slowing progression

Type of cataract: Age-related cataract

Equity focus: None specified

Review type: Other review

Quantitative synthesis method: Narrative analysis

Qualitative synthesis methods: Not applicable

Background

As the use of complementary and alternative medicine is growing, including in relation to eye diseases, it is important for ophthalmologists to know the evidence for the role of nutritional supplements and herbal medicines in common eye diseases.

Research objectives

To review the evidence for the role of nutritional supplements and herbal medicines in preventing, treating or delaying progression of age related macular degeneration, cataract, diabetic retinopathy and glaucoma.

Main findings

Authors included 23 studies which analysed the use of nutritional and herbal supplements in the treatment of common eye conditions. These were conducted in USA, Australia, Barbados, France, Finland and China.

The available evidence did support the use of certain vitamins and minerals in patients with certain forms of age-related macular degeneration. For cataracts, the available evidence did not support these supplements to prevent or treat cataracts in healthy individuals. For diabetic retinopathy and glaucoma, the available evidence did not support the use of these supplements. In the category of herbal medicines, the available evidence did not support the use of herbal medicines for any of these ocular diseases.

Because of the widespread use of nutritional supplements and herbal medicines, authors noted that ophthalmologists should be aware of their use so that they can inform patients properly when the supplements and herbal medicine are being used for eye disease. They also stated that a well-designed multicentre clinical trial on the use of nutritional supplements in eye disease is unlikely to be funded as prescription drug trials are the priority for research for most interested funders.

Methodology

Published studies and information found in PUBMED, International Bibliographic Information of Dietary Supplements, and selected websites were reviewed for the role of nutritional and herbal medicines in the treatment of age-related macular degeneration, cataract, diabetic retinopathy, and glaucoma. The studies were evaluated systematically for their study design, study population, benefits, risks, biases, and criteria for the categorization of the level of evidence. Studies were evaluated for their level of evidence as level I, II or III based on the American Academy of Ophthalmology (AAO) guidelines. Only studies with level of evidence I or II were reported in the paper.

Applicability/external validity

The authors did not discuss the applicability/external validity of the results.

 Geographic focus

Although authors included data from all income settings, results were mostly from high-income countries. The use of complementary supplements was likely to be much greater in high-income countries, therefore policy recommendations from this study might not be valid in low- or middle-income countries where patients do not have access to the supplements.

Quality assessment

This review was given low confidence in conclusions about the effects analysed as major limitations were identified. The review lacked clear outcomes for the search, inclusion criteria is not clearly reported and there was no evidence of more than one reviewer screening full-text articles for inclusion or extracting data of included studies. No sensible criteria were used to address bias, and the review was limited to a narrative summary of findings without appropriate discussion of the factors responsible for the differences in the results of the studies included. Additionally, the interpretation of the findings and conclusion were not clear.