Nearsightedness Related to Oxidative Stress and Low Dopamine in the Eye

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. 

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. 

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?

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 are essential to eye health. Help your eyes today and prevent tomorrow’s increased lens prescription or cataract development.