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Introduction

The omega-3 fats EPA and DHA are mainly obtained from coldwater fish, while the more commonly consumed omega-6 fats primarily come from vegetable oils, meats and dairy products. Evidence suggests that the high ratio of omega-6 fats to low levels of omega-3 fats currently consumed in the U.S. promotes a number of chronic diseases (1). For example, the cardio-protective benefits of consuming more omega-3 are well established. Studies looking at the relationship of omega-3 to the prevalence of advanced AMD have also observed a protective effect [see table below].

Omega-3 & Major Retinal Diseases

A newly published review of omega-3 functions in the retina from the NEI Division of Epidemiology and Clinical Research supports those observations. According to the reviewers, consistent evidence suggests that the omega-3 play a pivotal role in protecting the vascular and neural retina (2).

The authors discuss omega-3 related bioactive compounds in relation to three retinal diseases of major public health significance: ARMD, diabetic retinopathy and retinopathy of prematurity EPA and DHA may protect against factors and processes involved in the pathology of the retina's vasculature and nerve cells such as ischemia, damage from light exposure, reactive oxygen species and free radicals, inflammation and age-related retinal changes.

General Function of the Omega-3

Lipids found in cellular membranes reflect the type of dietary fats we consume. Tissue status of long-chain omega-3 can be modified by - and is dependent on - our dietary intake of these fatty acids. In nerve cell membranes omega-3 serve structural and function roles. They maintain membrane fluidity and flexibility, and modulate ion channels, receptors and ATPases. They also serve as precursors for the formation of eicosanoids, a family of hormone-like agents that act locally in the cells that make them or in adjacent cells. Eicosanoids influence processes such as inflammation, vessel dilation and constriction, clotting, the movement of calcium in and out of cells, and cell division and growth (1).

Omega-3 Role in the Retina

DHA is a major structural component of retinal photoreceptor outer segment membranes, and it affects the permeability, fluidity and thickness of these membranes. The omega-3 can influence such key processes as retinal cell signaling, gene expression, differentiation and retinal cell survival.

Omega-3 also affect the production and activation of angiogenic growth factors, vasoregulatory eicosinoids, and other factors implicated in abnormal retinal neovascularization, vascular permeability and inflammation. The formation of new and abnormal blood vessels, or angiogenesis, is common to 'wet' AMD, proliferative diabetic retinopathy and retinopathy of prematurity. Clarifying the role of omega-3 in retinal health and disease is important since tissue stores can be increased by consuming a better balance of omega-3 to omega-6.

References

1. Rand Evidence Report 114, commissioned by US Health Department. Effects of omega-3 fatty acids on cognitive function with aging, dementia and neurological diseases. AHRQ No. 05- E011-2, 2005
2. SanGiovanni JP and Chew EY. The role of omega-3 long-chain polyunsaturated fatty acids in health and disease of the retina. Prog in Retinal Eye Res 24:87-138, 2005