Authors' objectives:

The purpose of this study was to conduct a systematic review of the scientific-medical literature to identify, appraise and synthesize the evidence for the effects of omega-3 fatty acids on eye health. Questions assessed the possible primary or secondary preventive influence of the intake of omega-3 fatty acids on important eye health-related outcomes. These included age-related macular degeneration (ARMD), diabetic retinopathy, retinitis pigmentosa, cataracts, and occlusions of either retinal veins or retinal arteries. Adverse effects associated with omega-3 fatty acid supplementation in interventional studies of eye health were also sought.

Authors' results and conclusions: Sixteen studies, described in 16 published journal articles, were found to investigate nine of 23 potential questions. Question-specific qualitative syntheses of the evidence were derived. Greater interpretative emphasis was placed on evidence from randomized controlled trials (RCTs) and other designs that were both prospective and controlled. Too little, or flawed, available evidence precluded meta-analysis for each question.

Authors' recommendations: Based on the studies identified by this review, clinical research has only scratched the surface with respect to understanding the possible utility of the intake of omega-3 fatty acids as a primary or secondary prevention in eye health. Moreover, seen from the point of view of clinical researchs typical, linear arc - which moves from basic science to observational research to RCTs, and culminating in the systematic review/meta-analysis of the observations obtained by these primary studies - there is a paucity of solid observational research with which to construct an experimental framework affording the meaningful conduct of RCTs. For example, there is little understanding of the exact sources, types and doses of omega-3 fatty acids, or even the possible duration of their use, which might usefully serve as definitions of a prevention-centered intervention for any of the eye diseases/visual impairments examined in our review. Perhaps only with respect to the question of preventing the development/progression of advanced age-related macular degeneration (ARMD) is there some suggestive evidence, which is underscored by it being a strong public health problem, to allow researchers to consider conducting an RCT. At the same time, a single study reporting adverse event data likely does not permit laying to rest all possible concerns regarding the short- or long-term safety of omega-3 fatty acid interventions. It is therefore our view that much more research will need to be conducted before anything conclusive can be asserted with respect to the effects of omega-3 fatty acids on eye health. It is also our understanding that sorting out the possible benefits of the intake of omega-3 fatty acids in eye health might profit from taking into consideration the impact of the concurrent intake of omega-6 fatty acids and, by definition, the omega-6/omega-3 fatty acid intake ratio.

Authors' methods: Systematic review

Project Status: Completed

URL for project: http://www.ahrq.gov/clinic/tp/o3eyetp.htm

Year Published: 2005

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: United States

Organisation Name: Agency for Healthcare Research and Quality

Contact Address: Center for Outcomes and Evidence Technology Assessment Program, 540 Gaither Road, Rockville, MD 20850, USA. Tel: +1 301 427 1610; Fax: +1 301 427 1639;

Contact Name: martin.erlichman@ahrq.hhs.gov

Contact Email: martin.erlichman@ahrq.hhs.gov

Copyright: Agency for Healthcare Research and Quality (AHRQ)