By Dr. Mercola
Growing older is inevitable, but conditions often considered age-related may not be. One condition many people expect as they grow older is declining vision. However, contrary to popular belief, your vision is largely dependent on your lifestyle and not your chronological age.
Some of the more common reasons for vision loss as you age include cataracts, diabetic retinopathy, and two of the leading causes of blindness, macular degeneration and glaucoma.1 In a survey from Johns Hopkins University, scientists discovered that nearly half of Americans said losing their eyesight was the "worst possible" health problem someone could suffer.2 Becoming blind was dreaded more than HIV/AIDS, going deaf or losing a limb.
There are several commonsense strategies that help protect your vision, including quitting smoking, normalizing blood sugar and reducing or eliminating aspartame and processed trans fats. Your eyes respond to nutritional support, but recent research also demonstrates that moderate to vigorous intensity exercise may reduce your risk of glaucoma by as much as 73 percent.3
Structure and Function of Your Eyes
Your eyes are complex orbs, converting light to color and shapes your brain interprets as images. Each eye constantly adjusts the amount of light that is let in, focusing on objects near and far, transmitting the information near-instantaneously to your brain. There are many different structures within your eye responsible for the function of sight.4
Sight begins as light passes through the cornea, the clear, dome-shaped surface covering the front of your eye. Your cornea is responsible for bending light so it hits the retina, while your iris, the colored part of your eye, regulates the size of the pupil determining how much light enters. Directly behind the pupil is the lens, the clear part that focuses light further onto the retina.
On your retina, located in the back of your eye, is thin, photosensitive tissue with photoreceptor cells that convert light into electrical signals. These signals travel from the retina, over the optic nerve directly to the visual cortex in your brain where the signals are processed and interpreted for color, shape, movement and depth.
Your optic nerve is like a fiber optic cable with approximately 1 million nerve fibers that transmit this information. Your vision may be affected at any point in this process. For instance, people who are colorblind have a reduced number of photoreceptors in specific color fields, making it impossible for their brain to properly interpret color from electrical signals that have not been generated.
In the case of being nearsighted, there is a refractive defect in the lens. In other words, the lens doesn't bend the light so the image is formed on the retina, but in fact bends or refracts the light so the image is formed in front of the retina. This may cause you to see close object clearly but those further away are blurred.5
Exercise Reduces Risk of Glaucoma
A team of researchers from the University of California used nationwide survey data from the National Health and Nutrition Examination Survey (NHANES) to compare least active people against those who were most active for risk of glaucoma.6 The NHANES is a large study that has tracked the health and nutrition status of adults since the 1960s and is unique in that the participants also undergo routine physical examinations as well as interviews.7
For many years it was assumed lifestyle choices didn't affect eye pressure, but recently studies have demonstrated exercise would affect blood flow to, and pressure in, the eye. Lead author Dr. Victoria Tseng and her colleagues used the data from the NHANES to analyze the difference in risk based on the intensity of exercise.
Prior to 2003 the study used self-reported data to determine activity level, but since then participants have used a wearable device to measure physical activity. Using data from the devices, Tseng defined the level of activity based on the number of steps taken in one minute and walking speed.8 Taking 7,000 steps every day was considered equivalent to 30 minutes of moderate exercise five days a week.
Tseng and her colleagues found those who enjoyed the most moderate to vigorous activity, as defined by the study parameters, had a 73 percent reduction in risk of suffering from glaucoma. Results of the study were presented at the 121st annual meeting of the American Academy of Ophthalmology (AAO) in New Orleans.9 Tseng commented on the results during her presentation, saying:10
“Our research suggests that it is not only the act of exercising that may be associated with decreased glaucoma risk, but that people who exercise with higher speed and more steps of walking or running may even further decrease their glaucoma risk compared to people who exercise at lower speeds with less steps."
What Is Glaucoma?
Research has found exercise reduces pressure inside the eye, the primary symptom of glaucoma that causes damage and ultimately blindness. The disease damages the optic nerve when fluid builds in front of the eye and puts added pressure in the eye, damaging the nerve. In a healthy eye, a clear liquid called aqueous humor circulates in the anterior chamber (front portion) of the eye, between the iris and cornea just beneath.
A small amount of fluid is continuously produced and circulates through the chamber. To maintain a constant pressure, the same amount drains out of the area through two structures. The trabecular meshwork drains up to 85 percent of the aqueous humor and plays a vital role in modulating the amount of fluid that is either drained or stays within the anterior chamber of the eye.
Physical changes and altered signaling pathways in the trabecular meshwork may trigger a pressure increase in the anterior portion of the eye that then places pressure on the posterior chamber and ultimately on the optic nerve.11 Cells in the trabecular meshwork make and maintain the structure, providing a natural resistance to outflow of the aqueous humor. There is evidence this process is damaged in those suffering from primary open-angle glaucoma, the type that accounts for nearly 90 percent of all glaucoma cases.12
The term open-angle means the area where the iris meets the cornea is as wide and open as it should be. Damage in this type occurs slowly, during which symptoms and damage are not noticeable until you begin to lose vision. To detect this type of glaucoma early, it is necessary to have your eye pressure measured by a qualified professional on a regular basis.
Angle-closure glaucoma, also called narrow-angle glaucoma, is far less common and occurs acutely, requiring immediate medical attention.13 It is triggered by blocked drainage of the aqueous humor and quickly raises intraocular pressure. Symptoms are very noticeable and require immediate attention to prevent permanent blindness.
What Is Your Risk?
There are several factors that increase your risk for developing glaucoma. According to the AAO the factors that increase your risk include:14
Your risk is higher over age 40 if you are African-American and higher over age 60 for other groups.
• Medical Conditions
If you have a history of an eye injury, are nearsighted or farsighted, your risk of developing glaucoma increases. Other medical conditions that may increase your risk include diabetes, high blood pressure and heart disease. Prolonged use of corticosteroid drugs to treat other conditions may also be a factor.
This is a progressive thinning of your cornea that happens to 1 in every 2,000 people. It most commonly occurs in your 20s. Although the cause is unknown, researchers believe it may be triggered by a genetic predisposition and environmental influences. As the cornea thins, the anterior chamber of the eye distorts and increases the risk of increased pressure.15
• Optic nerve degeneration
Also called optic nerve atrophy, this condition causes glaucoma by directly affecting the health of the optic nerve. Degeneration can occur with or without increased pressure in the eye, but there is likely a mechanical damage where the optic nerve inserts into the back of the eye.16 A reduction to blood flow to the nerve may be a contributing factor to optic nerve degeneration. Some believe that in cases of normal-pressure glaucoma, damaged blood flow may play an important role.
Those with first degree family members with glaucoma have a higher risk than the general public. Age related open-angle glaucoma has more than one genetic mutation that confers risk for the condition. However, lifestyle choices have an impact on the expression of these genes.17
Best Choices to Support Eye Health
Exercise is not the only way to support the health of your eyes and vision. Some of the choices you make each day in the things you eat or the digital equipment you use can have compound impact on your eyes over the years. Here are some lifestyle choices you may consider to help protect your eyes:
Balance blue light exposure
Blue light is part of the visible light spectrum with a very short wavelength and higher amounts of energy.18 Scientists know this reaches deeper into your eye.19 Over time, exposure can damage your retina. Although not specifically linked to glaucoma, limiting exposure, especially after sunset, may help reduce your risk of age-related macular degeneration, another leading cause of blindness among seniors.
For more information on the link between blue light and eyesight see my previous article, "Are There Benefits to Blue-Blocking Glasses?"
Normalize blood sugar
Excessive sugar and insulin resistance can pull fluid from the lens of your eye, affecting your site and ability to focus. Long-term, excess sugar and diabetes may damage the blood vessels in your retina, obstructing blood flow and restricting your vision permanently. To discover how I reduce insulin resistance and blood sugar levels, see my previous article, "Half of all Adults will Develop Pre-Diabetic High Blood Sugar."
Lutein and zeaxanthin
These are potent antioxidant plant compounds. Lutein is found in green leafy vegetables such as spinach and kale, and other colorful vegetables such as carrots, broccoli, red and yellow peppers, tomatoes and spices.20 Many of these foods are also high in zeaxanthin.21 For more information about the importance of these nutrients to your sight and about supplementation, please see "How Your Diet Can Significantly Improve Your Vision."
This nutrient is produced by microalgae when the water supply dries up, protecting the algae from ultraviolet radiation. You may absorb some from wild-caught Alaskan salmon, but you may need supplementation to get the full benefit of the nutrient. Astaxanthin is a carotenoid that may be one of the most important nutrients to protect you against blindness.
While this powerful antioxidant does not protect against glaucoma, it may protect against cataracts, the second leading cause of vision loss.22 According to the National Eye Institute more than 50 percent of Americans will have cataracts by age 80.
Animal-based omega-3 fats
Diabetic retinopathy is a serious complication of Type 2 diabetes that occurs when blood flow to the retina is obstructed. In a study from the Journal of the American Medical Association, researchers found middle age and older individuals with Type 2 diabetes who consumed 500 milligrams per day of omega-3 fats from two servings of omega-3 rich fish a week, enjoyed an impressive 48 percent reduced risk of diabetic retinopathy.23
As a general rule, I recommend eating only authentic wild-caught Alaskan salmon or smaller fish with short life cycles, such as sardines, herring, mackerel or anchovies. These are good choices to get omega-3 fats while avoiding as many toxins as possible.
Benefits of Exercise Reach Beyond Physical Health
Although exercise benefits your physical health in innumerable ways, such as greater mobility, heart and eye health, weight control, blood sugar management and reduced risk of some cancers to name just a few, it also important to remember the mental and emotional benefits you enjoy. These, in turn, may help motivate you to continue your fitness journey.
Exercise is one of the most effective ways to improve your mental health and your motivation. Exercise decreases stress, fights depression and anxiety,24 improves sleep quality and increases your self-esteem.25 Each of these factors help motivate you to continue to exercise, make healthy lifestyle decisions, improve your productivity and creativity and may improve your performance at work.
Thus, while exercise has powerful benefits to your long-term physical health, it may also be the crucial factor to helping you make other lifestyle choices that have an impact on your everyday life.