Lifestyle and Dietary Considerations
A number of lifestyle and nutritional interventions can significantly reduce the risk of eye problems. These interventions include routine visits to an optometrist (OD) or ophthalmologist (MD) (Pelletier 2009), exercising regularly (Munch 2013), avoiding smoking (Velilla 2013), reducing exposure to ultraviolet (UV) light (Sui 2012), controlling blood sugar (Diabetes Control and Complications Trial Research Group 1993) as well as blood pressure and blood lipid levels (UK Prospective Diabetes Study Group 1998; van Leiden 2002; Munch 2013), and consuming a healthy diet (Moeller 2004).
Routine Eye Exams
Many eye problems, including glaucoma and diabetic retinopathy, may not have any symptoms until the condition has reached an advanced state. Since many eye problems can be treated or at least slowed by conventional and integrative treatments, it is important to get regular diagnostic exam tests and dilated eye exams. Many professional organizations recommend that everyone over age 60 or 65 receive a thorough eye exam at least every 1-2 years. Frequent eye exams are also essential for younger people with a family or personal history of eye problems, or those with hypertension and/or diabetes (Pelletier 2009; AOA 2014c; AAO 2014).
Exercise and Eye Exercises
Regular exercise may be useful in preventing or at least slowing the progression of macular degeneration, cataracts, and diabetic retinopathy. A study of 888 adults aged 30-60 years reported that macular drusen > 63 µm — which is regarded as a potential precursor of age-related macular degeneration (AMD) — were 67% less prevalent in subjects who exercised 7 or more hours per week compared to those who exercised 2 or less hours per week (Munch 2013). In a study that enrolled 32 610 runners and 14 917 walkers who were followed for 6.2 years, both moderate exercise (walking) and vigorous exercise (running) were associated with a significantly lower risk of cataracts (Williams 2013). In addition, a study of 1811 US diabetics (average age 70 years) reported that participants with diabetic retinopathy had a 46% lower likelihood of meeting exercise guidelines established by the American Diabetes Association (ie, 2.5 hours per week of moderate or vigorous exercise over at least 3 days/week along with resistance training at least 2 days per week) (Janevic 2013).
Physical exercise may also be helpful in reducing the risk and/or degree of myopia. Exercising for 10 minutes on a stationary bicycle was found to produce a small but significant reduction in myopia in 10 near-sighted young adults (Read 2011). Several other studies involving children and adults have also reported that the incidence of myopia is significantly lower among those who are physically active (Read 2011; Jones 2007; Jacobsen 2008).
Some authorities recommend eye exercises for reducing eye strain and fatigue such as frequently looking away from the computer screen and focusing on a distant object for several seconds or closing the eyes for brief periods every 20 minutes or so (MCSC 2014; Bhanderi 2008). Sometimes, eye exercises may be recommended to help improve vision or slow the decline in visual acuity that often occurs with aging. Overall, evidence in support of the notion that eye exercises can confer meaningful benefits for vision is relatively weak, but some data suggest positive effects (Rawstron 2005).
Although more evidence is needed, various eye exercises have been suggested such as sketching a figure 8 with the eyes, reading by candlelight, and using positive diopter lenses for near reading in individuals with myopia (Dailey 2014; Gopinathan 2012). A study of 10 myopia subjects reported that performing a group of 8 eye exercises daily for 3 weeks significantly reduced difficulty in distance vision by 50% and eye fatigue by 53% (Gopinathan 2012).
Avoiding Smoking and Excess Alcohol Consumption
A number of environmental factors can affect eye health. Smoking has been associated with a significantly higher risk of macular degeneration (Coleman 2010; Velilla 2013) and cataracts (Lindblad 2005). In women who smoked 6 to 10 cigarettes per day, quitting smoking for 10 years or more was associated with a significantly reduced cataract risk compared to current smokers (Lindblad 2005).
Higher alcohol consumption was also linked to a significantly higher risk of macular degeneration (Coleman 2010). A study of 20 963 adults reported that consuming more than 20 g of alcohol per day (about one to two drinks per day) was associated with a 21% increased risk of developing macular degeneration (Adams 2012). Evidence on alcohol consumption and diabetic retinopathy has been conflicting, with studies showing that alcohol consumption is associated with lesser or greater risk of diabetic retinopathy (Wang 2008). Several studies have reported that increased alcohol consumption does not seem to be related to higher risk of glaucoma, although some studies have reported an association between alcohol consumption and higher levels of eye pressure (Ramdas 2011; Wang 2008). A study of 3654 adults for 5 to 10 years reported that rates of cataract surgery were significantly lower in light alcohol drinkers (1 or 2 drinks daily) compared to adults who either drank no alcohol or drank more than 2 alcoholic drinks daily (Kanthan 2010).
Wearing UV-Blocking Glasses
It is important to protect the eyes from excessive ultraviolet (UV) light exposure. Several studies have reported that high exposure to UV rays from sunlight is associated with a significantly higher risk of macular degeneration and cataracts, and wearing UV blocking sunglasses can significantly reduce the risk of macular degeneration or cataract formation due to UV light exposure (Delcourt 2001; Neale 2003; Sui 2012).
Controlling Blood Sugar
Whether or not a person has diabetes, controlling blood sugar and avoiding refined sugars are critical for maintaining eye health. Various studies have shown that good blood sugar control and avoiding refined carbohydrates (those with a high glycemic index such as sugar or corn syrup) can significantly reduce risk of diabetic retinopathy, cataracts, and macular degeneration (Diabetes Control and Complications Trial Research Group 1993; Weikel 2013; Chiu, Milton 2007). The glycemic index is a measure of how quickly and how much blood glucose increases after eating 50 g of a particular food. Pure glucose is listed as a 100 on the glycemic scale. Foods with a high glycemic index include most sugars (glucose, fructose, sucrose, high-fructose corn syrup, maple syrup, and most forms of honey), many grain products, potatoes, fruit juices, and dried fruit. Foods with a low glycemic index include meat, poultry, fish, most unsweetened dairy products, nuts, seeds, berries, and green leafy vegetables (Harvard Health Publications 2014; Chlup 2008; Atkinson 2008).
A study of 726 people with insulin-dependent diabetes without retinopathy reported that tight blood sugar (glucose) control over an average 6.5-year follow-up was associated with a 76% reduced risk of developing diabetic retinopathy. The “tight blood sugar control” group had insulin provided 3 or more times daily by injection or pump, measured their blood glucose at least 4 times daily, and made frequent changes to insulin doses depending on their blood sugar levels. The “conventional blood sugar control group” received insulin only once or twice daily and made fewer blood sugar checks and insulin dose adjustments than the “tight blood sugar control group.” After 5 years of treatment, average hemoglobin A1C (HbA1c) levels were about 6.9% in the “tight blood sugar control group” and 9.0% in the “conventional blood sugar control group.” (The % of HbA1c is a measure of average blood sugar levels in the blood over a 3-month period. Life Extension® recommends that HbA1c concentrations should be kept below 5.7% to optimize health and reduce the risk of several age-related diseases; levels below 5.0% are even more ideal, but this may be difficult for many individuals to achieve.) This same research paper also reported that tight glucose control in 715 people who already had mild diabetic retinopathy reduced the progression rate of retinopathy by 54% (Diabetes Control and Complications Trial Research Group 1993).
Several studies have also reported that cataract formation is significantly more likely in people who have diabetes and/or consume higher amounts of carbohydrates, especially if the carbohydrates consist of simple sugars with a high glycemic index (Weikel 2013). One study reported that women who consumed more than 200 g carbohydrates daily had a 2.46-fold greater risk of getting cataracts compared to women eating less than 185 g carbohydrates daily (Chiu 2005). Another study, which followed 933 adults for a 10-year period, reported that persons who ate larger amounts of high glycemic index carbohydrates had a 77% greater risk of cataracts compared to those who ate mostly low glycemic index carbohydrates (Tan 2007).
Avoiding large amounts of refined sugars and other carbohydrates with a high glycemic index is also important for people trying to prevent macular degeneration progression. An 8-year prospective study of 3977 adults aged 55-80 years reported that persons in the group consuming the highest glycemic index diet had a 17% greater risk of getting large drusen (yellow deposits beneath the retina) in the eyes (Chiu, Milton 2007; NEI 2013). Furthermore, the authors estimated that by slightly decreasing the glycemic index of US adults, about 100,000 cases of advanced macular degeneration could be prevented in 5 years (Chiu, Milton 2007). Lowering intake of high glycemic index foods can involve simple steps such as avoiding refined sugars, refined grains, and sugar-laden beverages.
The Diabetes protocol provides a thorough discussion of comprehensive strategies for controlling blood glucose and HbA1c levels.
Controlling Blood Pressure and Blood Lipids
Diabetic retinopathy has also been associated with high blood pressure (hypertension) and high blood levels of cholesterol and other lipids (hyperlipidemia). A British study examined diabetic complications in 1148 hypertensive subjects with type 2 diabetes (average age 56 and average blood pressure 160/94 mm Hg at baseline) over an average follow-up period of 8.4 years. Subjects were randomly assigned to either a tight blood pressure control regimen (which primarily used the ACE-inhibitor drug capoten [Captopril®] or the beta-blocker atenolol [Tenormin®]) or a less-strict blood pressure regimen. Subjects in the tight blood pressure control regimen (average blood pressure 144/82 mm Hg) had 34% less diabetic retinopathy than those on the less-strict regimen (average blood pressure 154/87 mm Hg) (UK Prospective Diabetes Study Group 1998). In another large study of adults with type 2 diabetes (aged 50-75 years), subjects were randomly treated with either the cholesterol and triglyceride lowering drug fenofibrate (Tricor®) (200 mg/day; 4895 subjects) or placebo (4900 subjects) over a 6-year period. In the group receiving fenofibrate, 30% fewer participants required first laser treatment for proliferative retinopathy compared to participants in the placebo group (Keech 2007).
Several strategies for controlling blood pressure and blood lipids are outlined in the High Blood Pressure and Cholesterol Management protocols, respectively.
Controlling Homocysteine Levels
Homocysteine is an amino acid found in the blood that has been shown to negatively affect vascular health (Schalinske 2012). Sufficient levels of folate, vitamin B12, and trimethylglycine (TMG) help reduce blood levels of homocysteine (Brouwer 1999; Dierkes 1999; Bailey 2002; Weir 1998; Lever 2005; Detopoulou 2008). High homocysteine levels have been linked to many health problems including heart disease, peripheral vascular disease, and eye problems such as macular degeneration, diabetic retinopathy, and cataracts (Weir 1998; Gopinath 2013; Brazionis 2008; Sen 2008; Ambrosch 2001). A 10-year study of 1390 adults reported that AMD was 53% more common in subjects with high blood homocysteine (over 15 µmol/L), 89% more common in subjects with folate deficiency (below 11 nmol/L), and 82% more common in subjects with low vitamin B12 (below 185 pmol/L) (Gopinath 2013). A study reported that average blood homocysteine levels were almost 5 times higher in 40 subjects with cataracts compared to 20 controls (mean homocysteine of 25.1 µmol/L in subjects with cataracts and 5.4 µmol/L in controls) (Sen 2008). Another study of 168 diabetics (average age 66 years) found that blood homocysteine levels were significantly higher in subjects with diabetic retinopathy compared to subjects with normal vision (Brazionis 2008).
The Homocysteine Reduction protocol provides a comprehensive discussion about evidence-based strategies for controlling homocysteine levels.
Adhere to a Healthy Diet
Since many nutrients are involved in eye health, consuming a phytochemical-rich, plant-based diet is an important consideration for retaining visual acuity into advancing age. One study of 479 women (aged 52-73 years at baseline) without initial cataracts measured eating patterns and new cataract formation over a 9 to 11 year follow-up period. The women’s diets were analyzed for consumption of nutritious foods like fruits, vegetables, whole grains, and fish; a “Recommended Foods Score” was calculated for each woman. Researchers noted that the women with the highest levels of “Recommended Foods Score” had a 53% lower risk of cataracts than those with the lowest levels (Moeller 2004).
Many studies have reported that higher consumption of fruits or fruits and vegetables are associated with a significantly lower risk of eye problems such as macular degeneration, cataracts, glaucoma, and diabetic retinopathy. An 18-year prospective study of over 118 000 adults age 50 or older reported that consumption of 3 or more servings of fruits daily was associated with a 36% lower risk of macular degeneration compared to those who consumed ≤1.5 servings daily (Cho 2004). In a study of 599 adults age 65 or older, consuming the highest amount of fruit daily was associated with a 38% reduced risk of cataracts compared to consuming the least amount of fruit daily. Risk of cataracts was also reduced by 38% in those who ate the highest amount of vegetables daily versus those who ate the least (Pastor-Valero 2013). A cross-sectional study of 584 African-American women (age 65 or older) reported that the odds of having glaucoma were decreased by 79% in women who consumed ≥3 servings of fruits/fruit juice daily compared to those who ate <1 serving daily. Women who ate at least one serving a week of bitter greens like kale or collard greens, both very rich in the phytonutrients lutein and zeaxanthin, had a 57% lower risk of glaucoma compared to those who ate <1 serving a week (Giaconi 2012). An 8-year prospective study of 978 diabetics aged 40-70 years reported that the incidence of diabetic retinopathy was 52% lower in groups with the highest compared to the lowest levels of fruit consumption (Tanaka 2013).
Following a Mediterranean diet (rich in fruits, vegetables, whole grains, legumes, olive oil, and fish) may also reduce the risk of many eye diseases. One study of 500 adults with type 2 diabetes reported that following a Mediterranean type diet was associated with significantly lower rates of cataracts, glaucoma, and total blindness. Also, regular consumption of beans, okra, and plantains was also associated with a significantly lower risk of cataracts and glaucoma (Moise 2012).