Nearsightedness Related to Oxidative Stress and Low Dopamine in the Eye
Monday, March 13, 2017
Linda J. Dobberstein, Chiropractor, Board Certified in Clinical Nutrition
Nearsightedness is the primary cause of vision impairment throughout the world. It affected approximately 1.6 billion individuals in 2000 and is expected to increase to 2.5 billion, or 30 percent of individuals in the world, by 2020. Despite the advances in glasses, contacts and Lasik surgeries, nearsightedness is considered an unsolved medical mystery. Loss of visual acuity at any age affects life with daily need for glasses, contact lenses or even visual assistance aids.
New information pertaining to oxidative stress, natural light, and dopamine provides essential insight into prevention and management of nearsightedness. We can learn from this information and help protect our eyes and our children’s vision development for a brighter, more visually clear world.
Nearsightedness, or myopia, is the inability to clearly see things far away. You may have trouble seeing the TV, movie theater screen, white board, or traffic signs until you are up close. There are two basic types of nearsightedness, normal myopia and high myopia. Normal myopia is less serious and much more common. High myopia is a more significant issue. High myopia stretches eye tissues and creates progressive eye strain that is considered degenerative with a greater risk for retinal detachment, glaucoma, cataracts and even vision loss. High myopia has prescription strength of -6 dioptres or greater and is currently one of the main causes of visual impairment and blindness worldwide. The concerns and support needed are the same for both types of myopia. The goal is to stop the progression of both and help maintain clarity of sight.
Oxidative Stress Causes Nearsightedness
Compelling evidence strongly suggests that oxidative stress within the eye is the primary reason for vision breakdown, the development of nearsightedness, and potential complications like cataracts, retinal tears, and macular degeneration. Much of the oxidative stress can be traced back to increased amounts of reactive oxygen species (ROS) in the eye, especially the retina.
The retina, which is a layer of cells in the back of the eye that transmits an image to the optic nerve, requires a steady supply of oxygen. Oxygen is supplied by two layers of blood vessels inside and behind the retina. Retinal tissue in the eye has the highest oxygen consumption in the body; more than the heart, brain or muscles. As ROS elevates, it may impair blood flow to the retina, which adds another layer of stress.
The retina is exposed to continual light exposure, which also triggers high amounts of ROS. This combination of ongoing high oxygen and light exposure generates high amounts of oxidative stress to the eye structure. If there are adequate antioxidants, then the eye remains healthy, but if not, deterioration can occur.
The eye also contains large amounts of polyunsaturated fats (PUFAs) in its nerve tissue. Unsaturated fats are more susceptible to oxidative injury or lipid peroxidation, which contributes to tissue breakdown and more ROS production.
Science now sees that the cumulative damage of oxidative stress leads to a breakdown in visual acuity including both normal and high myopia, and greater risk of cataracts, retinal tears, and glaucoma in all ages. The speed of progression, though, depends on the status of key elements like dopamine, nitric oxide, and several nutrients.
Dopamine and Nitric Oxide
The neurotransmitter dopamine and the cellular signaling molecule nitric oxide are very involved with eye development and vision. Dopamine is directly involved within the retina and signaling cascade that controls critical eye growth in infancy and childhood. Dopamine generates signals that block the elongation of eye past the state when it has reached its optimal optical point. This is like dopamine at the controls of a manual camera lens or binoculars.
Optimal focus occurs in infancy by the age of 12-18 months. Researchers believe that during childhood when the eye is still maturing, if dopamine doesn’t get released adequately into the retina, the eye becomes elongated. Convergence and focus becomes strained and nearsightedness develops.
Dopamine talks with another neurochemical called nitric oxide within the eye. Nitric oxide works with an enzyme group, nitric oxide synthase (NOS). It regulates eye growth and acts as a smooth muscle relaxant, a vasodilator, and modulates nerve activity within the eye.
There are three different types of NOS. These include inducible or iNOS, endothelial or eNOS, and neuronal or nNOS. There needs to be a balance between the three types. nNOS and eNOS are the beneficial types that help nerve communication and blood flow. iNOS promotes tissue inflammation and destruction and overly aggressive immune response. Excess iNOS and insufficient nNOS and eNOS are linked with several eye disorders including nearsightedness. Choline is a major supporter of healthy nitric oxide and NOS.
Prevention of Nearsightedness
The rates of nearsightedness are rising across the world. In Asia, it is estimated that a stunning 80 percent of the population has myopia, and of this group, 20 percent has severe myopia. This has left scientists scrambling to find ways to stop the development and progression of myopia. In addition to various types of glasses, Lasik surgery, eye care professionals may use medications that increase dopamine and/or choline in the eyes. Most importantly, nutrition and outdoor light exposure play a massive role in prevention of myopia and need to be at the forefront of healthy eye development and maintenance in all ages.
Earlier we saw that excess amount of ROS is highly problematic for the eye. Several types of antioxidants and enzymatic antioxidants are required to quench and detoxify ROS. These include copper/zinc SOD, manganese SOD, glutathione, vitamins A, C, and E, and beta carotene. Of these nutrients, zinc is the most critical, as the retina has an especially high need for zinc. Zinc deficiency increases the risk of damage to the DNA, proteins, lipids and connective tissues of the eye. Inadequate zinc leads to higher risks of vision changes, progressive myopia and complications with macular degeneration and cataracts. In addition, adequate zinc is needed to activate the other antioxidants and enzyme systems that help protect the eye nerve tissue.
Bilberry and Grape Seed Extract Protect Circulation and Quench Free Radicals
Berry rich foods and the antioxidant anthocyanoside from bilberry are recommended in addition to zinc to help protect eyesight. Bilberries have been shown to help and protect vision by increasing circulation to the retina capillaries and quenching free radicals. Studies show benefit for nearsightedness, cataracts, glaucoma and helping improve night vision. Grape seed extract, a proanthocyanidin antioxidant, also helps protect the retina from free radical damage and support. When grape seed extract was combined with zinc, it was found to stop the degenerative progression of vision loss and cataract development.
Dopamine Production Requires Outdoor Light Exposure and Nutrients
One of the goals for healthy vision and prevention of myopia, especially in children, is to optimize dopamine production and function. Researchers note that the best way to stimulate dopamine naturally in the eye is through outdoor light exposure. This exposure acts to stimulate light receptors and the natural circadian rhythm within the eye, which affects dopamine production in the retina. Because of this finding, numerous studies recommend outdoor activity as a therapy to help protect children against nearsightedness. Other compounds that help the brain produce dopamine are tyrosine, zinc, iron, and copper, vitamins B3, B6, and C. Pantethine may be helpful in protecting nerves that contain dopamine.
Violet Light is Helpful
Another outdoor element found beneficial to eye health is violet light. Outdoor violet light exposure was shown to prevent and control nearsightedness. A new two-part study demonstrated in animal models that violet light exposure prevented the eye muscles from elongation and blocked myopia progression. Researchers then completed the second part of the study with nearsighted children. Children who wore contact lenses that allowed violet light into the eye stopped the progression of nearsightedness, versus those who wore contact lenses that partially blocked violet light. This evidence is contrary to present day recommendations of sunglasses and tinted windows that block violet light. Certainly, this information requires a discussion with your eye doctor.
It may be observed that in family histories over several generations, we see a trend of an increased number of family members wearing glasses. With modernization, we have become indoor creatures, almost afraid of the sun and ultra violet light. Curtains or blinds are pulled shut and little outdoor activity occurs for many. Computer screens or other high tech devices with blue light are daily encounters that offer their own challenges. Some say the rise in myopia is due to better screening and health care, but is it?
Choline for the Eye
Scientists have recommended nutrients like activated choline to help dopamine levels in the eye. Animal studies show choline improved the levels of dopamine within the retina, which may slow the progression of nearsightedness. Choline and omega-3 fish oils also help repair the damaged lipid or cell membranes in the eye from ROS.
Activated choline, like alpha-GPC and acetylcholine, helps support nitric oxide production and improve nerve activity and blood flow within the eye by supporting eNOS and nNOS. Animal studies also show that the amino acid arginine helps block the progression of nearsightedness, as arginine supports NO function. Nutrients like coenzyme Q10, anthocyanidins/grape seed extract and exercise help the body naturally make beneficial NOS forms and manage NO.
Astaxanthin deserves mention here for protection against retinal oxidative damage. We have seen information that high oxidative stress levels in the retina diminishes blood flow to the area, further stressing the eye, and increasing nearsightedness. Research shows that astaxanthin protects the retina against altered blood flow that leads to nerve cell injury and death. Recent cellular studies also showed that astaxanthin significantly reduced retinal damage and nerve injury from high levels of reactive oxygen species. There is a lack of research information directly on myopia, but astaxanthin certainly protects the retina from ROS in other eye disorders.
The act of wearing glasses or contacts day after day for the rest of your life often goes unnoticed until a contact is lost or glasses are broken. For many with nearsightedness, broken glasses or lost contacts would prevent them from safely or accurately driving, reading, working, cooking, or even walking to and from simple distances. If we can prevent this degenerative process from starting in our children or worsening in ourselves, it may prevent a lifetime of challenges or even blindness. Numerous factors affect visual acuity, but this research provides great direction in how we can help our eyes. Natural outdoor light and nutrients like zinc, alpha GPC/choline, astaxanthin, grape seed extract, berries, natural carotenes and fish oil are essential to eye health. Help your eyes today and prevent tomorrow’s increased lens prescription or cataract development.
Zinc – The trace mineral zinc is involved with over 300 processes in the body with some of the highest need of it in the retina. Children have great need for zinc as it is essential for growth. Insufficient dietary intake, athletes, growing children, sweating, chronic infections, allergies, and toxins increase the demands of zinc. White spots on nails and body odor are classic signs of significant zinc deficiency.
Astaxanthin – Astaxanthin is from the carotene antioxidant family. It has a long list of benefits for eye support including retina protection and it helps block excess negative effects of UV light, and reduces eye strain. It works synergistically together with other carotenoids like zeaxanthin, lutein, and beta carotene for eye health.
Choline – Choline is similar to B vitamins. It is required for nerves and brain tissue function. It plays essential roles in nitric oxide regulation and cell membrane stability of nerves, especially within the eye.
Beta Carotene – This crucial antioxidant works together with vitamin A and astaxanthin to help protect the eyes against the ravages of oxidative stress and ROS. Beta carotene is found in yellow, orange, red, and green leafy vegetables and fruits. If your diet lacks daily intake of 5-13 servings of these foods, it is likely supplemental support is needed.
Bilberry – Known also as the British blueberry or huckleberry, this antioxidant has been traditionally prized for its eye health benefits. It has been shown helpful for capillary protection, healthy circulation, and oxygenation of tissues – critical for the eye and retina. One of its historical uses is night-time vision support and visual acuity.
Read More: Eye Health News
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