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Studies on Omega-3 for Eye Health
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- Chong EWT, Kreis AJ, Wong TY, Simpson JA, Guymer
RH. Dietary omega-3 fatty acid and fish intake in the primary prevention of
age-related macular degeneration - A systematic review and meta-analysis. Archives
of Ophthalmology. 2008; 126(6): 826-833.
Abstract: Objective: To
systematically review the evidence on dietary omega-3 fatty acid and fish
intake in the primary prevention of age-related macular degeneration (AMD). Methods: Seven databases were systematically searched with no limits on
publication year or language using standardized criteria. Randomized controlled
trials and prospective cohort, case-control, and cross-sectional studies were
included. Of 2754 abstracts identified, 3 prospective cohort, 3 case-control,
and 3 cross-sectional studies met the criteria. Measures of associations were
pooled quantitatively using meta-analytic methods. Results: Nine studies provided data on a total sample of 88 974 people,
including 3203 AMD cases. A high dietary intake of omega-3 fatty acids was
associated with a 38% reduction in the risk of late AMD(pooled odds ratio [OR],
0.62; 95% confidence interval [CI], 0.48-0.82). Fish intake at least twice a
week was associated with a reduced risk of both early AMD (pooled OR, 0.76; 95%
CI, 0.64-0.90) and late AMD (pooled OR, 0.67; 95% CI, 0.53-0.85). Conclusions: Although this meta-analysis suggests that consumption of fish and
foods rich in omega-3 fatty acids may be associated with a lower risk of AMD,
there is insufficient evidence from the current literature, with few
prospective studies and no randomized clinical trials, to support their routine
consumption for AMD prevention.
- Flood VM, Mitchell P. Dietary fatty acids and
age-related macular degeneration. Agro Food Industry Hi-Tech. 2008; 19(2):
42-43.
Abstract: Age-related macular degeneration (AMD) is a leading cause of
vision loss and blindness among older people. It is important to identify
modifiable risk factors which could prevent or slow the progression of this chronic
disease. Dietary fatty acid intakes have been investigated in epidemiological
studies as it is plausible that individual lipids have properties which
modulate cellular damage in the eye. This
paper reviews epidemiological studies investigating links between fatty acids
and AMD, Mixed evidence has related the sub-types of saturated and
monounsaturated fatty acids to AMD, but nearly all epidemiological studies have
demonstrated some level of AMD protection from omega-3 polyunsaturated fatty
acids (particularly long-chain fatty acids) and fish, with a tendency for a
corresponding dampening effect with increased dietary omega-6 polyunsaturated
fatty acids.
- Nguyen CTO, Bui BV, Sinclair AJ, Vingrys AJ. Dietary
omega 3 fatty acids decrease intraocular pressure with age by increasing
aqueous outflow. Investigative Ophthalmology & Visual Science.
2007; 48(2): 756-762.
Abstract: PURPOSE. To determine whether there is an association
between dietary omega-3 (omega-3) fatty acid intake, age, and intraocular pressure
(IOP) caused by altered aqueous outflow. METHODS. Sprague-Dawley rats were fed either omega-3-sufficient (omega-3(+)) or
omega-3-deficient (omega-3(-)) diets from conception. The diets had 7% lipid
content. The omega-3(+) diet contained safflower, flaxseed, and tuna oils (5.5:
1.0: 0.5), and the omega-3(-) diet contained safflower oil only. Intraocular
pressure was measured at 5 to 40 weeks of age under light anesthesia
(omega-3(+), n = 39; omega-3(-), n = 48). Aqueous outflow was determined at 45
weeks in a subgroup of animals (omega-3(+), n = 15; omega-3(-), n = 22) using
pulsed infusion. Ciliary body tissues (n = 6 per group) were assayed for fatty
acid content by thin-layer and gas-liquid chromatography in both diet groups. RESULTS. Animals raised on omega-3(+) diets had a 13% decrease in IOP at 40
weeks of age (13.48 +/- 0.32 mm Hg vs. 15.46 +/- 0.29 mm Hg; P < 0.01). When
considered as a change in IOP relative to 5 weeks of age, the omega-3(+) group
showed a 23% decrease (P < 0.001). This lower IOP in the omega-3(-) diet
group was associated with a significant increase (+56%; P < 0.001) in
outflow facility and a decrease in ocular rigidity (-59%; P < 0.001). The
omega-3(-) group showed a 3.3 times increase in ciliary body docosahexaenoic
acid (P < 0.001). CONCLUSIONS. Increasing dietary omega-3 reduces IOP with age because of
increased outflow facility, likely resulting from an increase in docosanoids.
This indicates that dietary manipulation may provide a modifiable factor for
IOP regulation. However, further studies are needed to consider whether this
can modify the risk for glaucoma and can play a role in treatment of the
disease.
- Hodge WG, Barnes D, Schachter HM, Pan YI,
Lowcock EC, Zhang L, Sampson M, Morrison A, Tran K, Miguelez M, Lewin G. Evidence
for the effect of Omega-3 fatty acids on progression of age-related macular
degeneration - A systematic review. Retina-The Journal of Retinal and Vitreous Diseases.
2007; 27(2): 216-221.
Abstract: Background: As part of a larger systematic review on the
effect of omega-3 fatty acids on eye health, the
aim of this report was to appraise and synthesize the evidence for the effects
of omega-3 fatty acids in slowing down the progression of age-related macular
degeneration (AMD) and/or decreasing the rate of progression to advanced forms
of AMD. Methods: A comprehensive search was undertaken in six databases (MEDLINE,
PreMEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, CAB Health,
and Dissertation Abstracts). Results: Two unique studies, one randomized clinical trial (RCT) and one
prospective cohort study, satisfied the eligibility criteria and were included
in the review. The RCT reported evidence on the effect of omega-3 fatty acids
in slowing down the progression of AMD. The prospective cohort Study addressed
the question: what is the evidence that omega-3 fatty acids decrease the rate
of progression to advanced forms of AMD? Conclusions: Clinical research on this topic is scarce. Only two studies were
eligible to be included in this review. Although one study result indicated
efficacy of preventing AMD progression to its advanced form, this result needs
to be duplicated and supported by future research.
- Mukherjee PK, Marcheselli VL, Barreiro S, Hu J,
Bok D, Bazan NG. Neurotrophins enhance retinal pigment epithelial cell survival
through neuroprotectin D1 signaling. Proceedings of the National Academy of
Sciences of the United States of America 8/7/2007. 2007; 104(32): 13152-13157.
Abstract: Integrity of retinal pigment epithelial cells is necessary
for photoreceptor survival and vision. The essential omega-3 fatty acid,
docosahexaenoic acid, attains its highest concentration in the human body in
photoreceptors and is assumed to be a target for lipid peroxidation during cell
damage. We have previously shown, in contrast, that docosahexaenoic acid is
also the precursor of neuroprotectin D1 (NPD1), which now we demonstrate, acts
against apoptosis mediated by A2E, a byproduct of phototransduction that
becomes toxic when it accumulates in aging retinal pigment epithelial (RPE)
cells and in some inherited retinal degenerations. Furthermore, we show that
neurotrophins, particularly pigment epithelium-derived factor, induce NPD1
synthesis and its polarized apical secretion. Moreover, docosahexaenoic acid
(DHA) elicits a concentration-dependent and selective potentiation of pigment
epithelial-derived factor-stimulated NPD1 synthesis and release through the
apical RPE cell surface.
- Bazan NG. Cell survival matters: docosahexaenoic
acid signaling, neuroprotection and photoreceptors. Trends in Neurosciences.
2006; 29(5): 263-271.
Abstract: Recent data have provided important clues about the
molecular mechanisms underlying certain retinal degenerative diseases,
including retinitis pigmentosa and age-related macular degeneration.
Photoreceptor cell degeneration is a feature common to these diseases, and the
death of these cells in many instances seems to involve the closely associated
retinal pigment epithelial (RPE) cells. Under normal circumstances, both cell
types are subject to potentially damaging stimuli (e.g. sunlight and high
oxygen tension). However, the mechanism or mechanisms by which homeostasis is
maintained in this part of the eye, which is
crucial for sight, are an unsolved riddle. The omega-3 fatty acid family member
docosahexaenoic acid (DHA), which is enriched in these cells, is the precursor
of neuroprotectin D1 (NPD1). NPD1 inhibits oxidative-stress-mediated
proinflammatory gene induction and apoptosis, and consequently promotes RPE
cell survival. This enhanced understanding of the molecular basis of endogenous
anti-inflammatory and neuroprotective signaling in the RPE presents an
opportunity for the development of therapies for retinal degenerative diseases.
- Brown NP. Essential fatty acids and eye health. Optician 7/21/2006.
2006; 232(6061): 36-38.
Abstract: The article focuses
on the importance of essential fatty acids (EFA) to eye health. The ways in
which EFA benefit the eye are mentioned. The characteristics of omega-3 and
omega-6 fatty acids are compared. The roles of fatty acids in the eye
development, meibomian gland function and tear production are discussed.
- Hodge WG, Barnes D,
Schachter HM, Pan YI, Lowcock EC, Zhang L, Sampson M, Morrison A, Tran K,
Miguelez M, Lewin G. The evidence for efficacy of omega-3 fatty acids in
preventing or slowing the progression of retinitis pigmentosa: a systematic
review. Canadian Journal of Ophthalmology-Journal Canadien D Ophtalmologie.
2006; 41(4): 481-490.
Abstract: Background: Studies in preterm and term human infants have
suggested that a dietary supply of omega-3 fatty acids is essential for optimal
visual development. Several basic science studies support the hypothesis that
omega-3 fatty acids may be useful therapeutic agents for pathologies of the
retina and lens. As part of a systematic review of the effect of omega-3 fatty
acids on eye health, the purpose of this study was to conduct a systematic
review of the scientific-medical literature to appraise and synthesize the
evidence for the effects of omega-3 fatty acids in preventing the development
or progression of retinitis pigmentosa. Methods: A comprehensive search was undertaken in MEDLINE, PREMEDLINE, EMBASE,
Cochrane Central Register of Controlled Trials, Global Health, and Dissertation
Abstracts. Unpublished literature was sought through manual searches of
reference lists of included studies and key review articles and from the files of
content experts. Searches were not restricted by language of publication,
publication type, or study design. Eligibility criteria were applied to screen
eligible studies on two levels. Data extraction and quality assessment were
performed. Results: Six studies published between 1995 and 2004 met eligibility criteria
in investigating the question of the possible value of omega-3 fatty acids in
slowing the progression of retinitis pigmentosa. Meta-analysis was not
performed because there was not enough available information for formal
quantitative analysis. Interpretation: There are trends in improvement of some retinitis pigmentosa
outcomes with omega-3 fatty acids in the higher quality studies. Clinical
research is preliminary in this field, however. Accordingly, definitive answers
will require significantly more observational and interventional clinical
research.
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