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It has been well documented that the average American diet is out of balance when it comes to the intake of omega-6 and omega-3 fatty acids. Throughout the 20th century, the increased use of refined vegetable oils in processed foods has increased the percentage of omega-6 in our diets. It is understandable that with our fast-paced lives, people are looking for convenient foods that can be consumed quickly, which leads to increased intake of processed foods high in omega-6 and saturated fats (e.g., chips, crackers, cookies, frozen dairy products, etc.). Americans also grew up on a "meat and potatoes" diet and prefer red meat, which contains arachidonic acid (AA). AA is another form of omega-6, which can have negative effects if consumed in large quantities. It is no surprise that 80% of American diets are lacking in quality omega-3 essential fatty acids (EFAs), which are high in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
Essential in essential fatty acids is the key word to better understand this dietary problem. Our bodies do not produce EPA and DHA, so we must obtain these nutrients from our diet or through dietary supplements. EFAs are critical to almost every body system and function, from cell membranes to regulating inflammation. Bodies that are deficient in EFAs can lead to a host of adverse health conditions including:
- dry skin
- elevated triglycerides
- poor memory/unclear thinking
- inflexible joints
- delayed infant development
- inconsistent mood and behaviors
- poor motor skills
EFAs have particular relevance for the eyes and ocular tissues. To illustrate this, consider that EPA and DHA attain their highest concentration in the ocular tissues – more than any other site in the body. Consider the important actions that each EFA has on the eye and vision systems:
o needed for neural and visual development
o a structural lipid in retinal photoreceptor and synaptic membranes
o protects against harmful light wavelengths, oxygen/free radicals, and age-associated damage to the eyes
o potent anti-inflammatory action
o reduces inflammation in the vessel walls, lacrimal gland, meibomian gland, and ocular surface
Another fatty acid that should be considered is gamma-linoleic acid (GLA). While GLA is an omega-6, it has many properties of omega-3s and can provide anti-inflammatory, antiproliferative, and upregulatory actions, which allow the body's production of important antioxidants. Most individuals produce GLA from dietary linolenic acid (LA); however, individuals with high body mass index (BMI) or nutrition deficiencies such as zinc and magnesium can't produce GLA and could benefit from this fatty acid in a supplement form. Three oils provide quality GLA: borage, evening primrose, and blackcurrant seed. Remember that GLA is an omega-6, which can lead to further imbalance of the omega-6/omega-3 ratio, so selective prescribing is recommended.
Anterior Eye Surface
There is a group of chronic ocular diseases, categorized as ocular surface disease (OSD), that affect the outer eye and cause discomfort, light sensitivity, and blurred vision if not appropriately managed. Most people speak of these conditions as "dry eye," as this is the most common symptom. OSD is a prevalent problem for millions of Americans, with studies validating between 15% and 30% of individuals diagnosed or reporting multiple symptoms of ocular surface disease daily.1-3 Females are more likely to experience OSD, and aging is a key factor as well. While there are multiple treatment options available for these diseases, concentrated triglyceride-form omega-3 supplements with EPA + DHA levels at, or above, 2000 mg per day are some of the best initial and long-term therapies available.
Treatment almost always begins with tear replacements or supplements (artificial tears). For cases of non-inflammatory dry eye, or those individuals with aqueous deficiency, a supplement drop several times a day will provide relief from most symptoms; however, there are many challenges with finding a quality tear-replacement supplement. Confusion often begins with the myriad of choices when one shops for artificial tears, with many containing antihistamines and decongestants that "get the red out," which creates vasoconstriction of the conjunctival blood vessels. This results in a drop that feels cooling and lubricious on initial insertion, but which ultimately results in rebound dryness after a short period of time. Most artificial tears also contain preservatives, which allow for convenient use, recapping, and storage. Unfortunately preservatives can create long-term irritation if applied more frequently than 3 to 4 times daily. Finally, residence time varies among products. Residence time is the time that a drop lubricates and remains on the surface of the cornea prior to being wiped away from the ocular surface by the normal blinking action of the eyelids. Many of the artificial tears on the market have good lubricating properties, but lack long residence times.
When it comes to dry eye, the lack of secretion from glands of the eyelids is often a source of discomfort, dryness, and blurred vision. The outer layer of the tears is an oily substance secreted by the meibomian glands, which are vertically oriented in the upper and lower lids. These glands have openings located just behind the lashes to allow for the oil to flow into the tear liquid and provide a covering that prevents evaporation and provides a surface tension effect to avoid tears' regularly spilling onto a person's cheek. If these glands become inflamed, the oil thickens and the secretion is greatly reduced. Use of an oil-based tear supplement can assist with replacing the missing oil in the tear chemistry; however, these supplements do nothing to address the underlying problem, which is inflammation and the thicker meibum. This begins the cascade that can lead to a partial or complete occlusion of the meibomian gland, which is classified as a hordeolum or chalazion. These conditions can lead to moderate to extreme discomfort, and in advanced cases can create pressure on the cornea to alter the shape, which can blur vision.
There are a number of options to treat lid conditions that are classified as meibomian gland disease (MGD). Some of these are more maintenance-based such as warm compresses and lid hygiene. MGD is a chronic condition that requires vigilance to manage. If basic lid hygiene does not prevent recurrence and comfort, the underlying cause is inflammation.
There are a number of options to reduce the inflammation associated with MGD; these include:
- topical steroids
- topical azithromycin
- oral omega-3 supplementation at levels of 3000 to 4000 mg/day
- oral doxycycline
Since topical steroids, topical azithromycin, and oral doxycycline should be used in a shorter course of therapy to reduce inflammation, omega-3 therapy at a dosage of 3000 to 4000 mg EPA + DHA daily can arrest and control inflammation and be used in long-term management of MGD.4 Omega-3 therapy is often initiated along with one of the other three methods listed above to quickly manage the inflammatory cascade with a taper of the topical or oral medications after 30 to 45 days. There are numerous peer-reviewed studies and subsequent papers that show both objective and subjective improvement of MGD following omega-3 supplementation.5-8
If inflammation exists on the ocular surface, there are several options to reduce inflammation. As described above, most of the treatment options must be used in limited duration in the treatment and management of MGD, due to potential long-term adverse effects. Only cyclosporine and omega-3 therapy are appropriate for long-term treatment.
Posterior Eye Segment
The retina reveals an even more compelling relationship to omega-3 fatty acids, with the focus on DHA. There is a rapid accumulation of DHA in the brain and retina during gestation and early postnatal life.9 In fact, several studies validate that a higher concentration of DHA in infant formula resulted in improved levels of visual acuity, compared with formula that did not contain DHA.10 Another study looked at preterm infant visual acuity with and without DHA added to the formula, and found similar improved visual acuity with the DHA supplement added to the formula.11
The retina is highly vascularized with supply from the central retinal artery above and a vast network of capillaries – the choroid – beneath the organ structure that receives the visual images and transmits the signal to the occipital lobe of the brain. Several longstanding studies demonstrate that blood flow and circulation in the retina improve following supplementation with fish oil.12
Our bodies battle oxidative stress every moment of daily life, and the retina faces this challenge as well. Thankfully, DHA is converted into a lipid mediator that is responsible for protecting the delicate retinal pigment epithelial cells from oxidative damage.13 DHA is most highly concentrated in the brain, photoreceptors, and retinal synapses; and, to no surprise, DHA accounts for 35% to 40% of the fatty acids within the eye structures. This concentration can only occur if the balance of omega-6 to omega-3 is controlled and at lower ratios of omega-6. Lower levels of omega-6s or LA improved the incorporation of omega-3s into the tissues with upregulation of most gene expression.
The retinal pigment epithelium (RPE) is the basement membrane of the retina and is critical to protection, support, and general health of the retinal receptors. A 2010 study describes the ability of the RPE cells to synthesize neuroprotectin D1 from DHA. Neuroprotectin D1 is shown to be a potent mediator, which evokes cell-protective, anti-inflammatory, prosurvival repair signaling, including the induction of antiapoptotic proteins and inhibition of proapoptotic proteins.13 Without a stable, protective foundation, rod and cone receptor cells directly above the RPE will gradually lose the ability to receive and transmit.
A large portion of the American population is about to experience a significant increase in a condition known as macular degeneration. Wikipedia defines macular degeneration, or age-related macular degeneration (AMD), as: "a medical condition that usually affects older adults and results in a loss of vision in the center of the visual field (the macula) because of damage to the retina. It occurs in 'dry' and 'wet' forms. It is a major cause of blindness and visual impairment in older adults (>50 years). Macular degeneration can make it difficult or impossible to read or recognize faces, although enough peripheral vision remains to allow other activities of daily life."
The dry form of AMD is much more common, as demonstrated by the current numbers in the US:
- 13.5 million with dry AMD
- 1.5 million with wet AMD
Due to the aging of the US population, combined with a new risk – high-energy visible light (HEV) – the number of new AMD cases is projected to be 2.7 million annually through the year 2050.14 At the current pace, we will have over 120 million individuals with AMD by the middle of the century, which will place a great practical and financial burden on the nation.
Macular degeneration, as the definition describes, creates decreased central vision, meaning the area that a person looks directly at will be blurred or dark. Imagine trying to read a newspaper but the words are very blurry or you have a dark smudge in the center of the page. This will affect all daily vision tasks from driving to watching television, to the one task that makes a person cringe – the ability to use your smartphone as you do today!
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