Eye Health

Eye Health

1 Overview

Summary and Quick Facts

  • As of 2010, an estimated 1.28 million U.S. adults over age 40 were blind and another 2.9 million had very poor vision. Adults with poor vision are at a significantly higher risk for many social and health problems including depression, social withdrawal, accidents and self-administered medication errors.
  • This protocol focuses on preventive measures aimed at maintaining generally healthy vision with aging.
  • Nutrient interventions such as omega-3 fatty acids; carotenoids; vitamins A, B-complex and E; and coenzyme Q10 have been shown to support eye health with aging. In addition, lifestyle interventions such as exercise, avoiding smoking and limiting intake of refined sugars have been demonstrated to significantly reduce the risk of several types of age-associated eye disease.

As of 2010, an estimated 1.28 million US adults over age 40 were blind and another 2.9 million had very poor vision; about 10‒20% of adults 80 or older had poor vision (NEI 2014). Adults with poor vision are at a significantly higher risk for many social and health problems including depression, social withdrawal, accidents, and self-administered medication errors (Casten 2013; Rosenberg 2008; Rowe 2004; Campbell 2005; Field 2007).

Fortunately, nutrient interventions such as omega-3 fatty acids, carotenoids, and B-complex vitamins have been shown to support eye health during aging (Christen 2009; Weikel 2012; Ma 2013; Nolan 2013; Hammond 1997).

Types of Eye Problems

  • Macular degeneration. Macular degeneration is characterized by loss of function in the central portion of the retina (called the macula) (AMDF 2014). People with macular degeneration experience a gradual loss of vision, especially in the central visual field. More information is available in the Macular Degeneration protocol.
  • Cataracts. Cataracts are caused when protein fibers in the lens undergo harmful changes that cause them to become cloudy and impair vision. More information is available in the Cataracts protocol.
  • Glaucoma. Glaucoma may be caused by a gradual increase in eye pressure which causes damage to the optic nerve (Chiang 2013). People with glaucoma experience reduced vision, especially in the outer (peripheral) field of view. More information and treatment strategies are outlined in the Glaucoma protocol.
  • Diabetic retinopathy. Diabetic retinopathy damages vision in persons with long-term type 1 or type 2 diabetes. It involves damage to tiny blood vessels, formation of advanced glycation end products, oxidative damage to cells, and inflammation (Bandello 2013). More information is available in the Retinopathy protocol.
  • Inherited eye conditions. These genetic conditions include retinitis pigmentosa and others. Retinitis pigmentosa first causes night blindness, then progressive loss of the outer field of view during daytime, and may lead eventually to total blindness (Hamel 2006).

Lifestyle and Dietary Considerations

  • Routine eye exams, since many eye problems may not have symptoms until the condition has reached an advanced state (Pelletier 2009)
  • Regular exercise may be useful in preventing or slowing the progression of macular degeneration, cataracts, and diabetic retinopathy (Munch 2013; Williams 2013; Janevic 2013).
  • Avoid smoking as it has been associated with a significantly higher risk of macular degeneration (Coleman 2010; Velilla 2013) and cataracts (Lindblad 2005). Higher alcohol consumption is also linked to a higher risk of macular degeneration (Coleman 2010).
  • Wearing UV-blocking sunglasses can significantly reduce the risk of macular degeneration or cataract formation (Delcourt 2001; Neale 2003; Sui 2012).
  • Controlling blood sugar, blood pressure, and cholesterol can significantly decrease the risk for diabetic retinopathy, cataracts, and macular degeneration (Diabetes Control and Complications Trial Research Group 1993; Weikel 2013; Chiu, Milton 2007; UK Prospective Diabetes Study Group 1998; Keech 2007).

Integrative Interventions

  • B-complex vitamins: In one study, women aged ≥40 years at baseline were treated with either a daily supplement containing folic acid, vitamins B6 and B12, or placebo. After an average 7.3-year follow-up period, risk of developing macular degeneration was 33% lower in the supplement group (Christen 2009). Also, benfotiamine, a fat-soluble form of thiamine, has been shown to prevent diabetic retinopathy in animal research (Hammes 2003).
  • Omega-3 fatty acids: Studies have revealed higher consumption of omega-3 fatty acids is associated with significantly lower rates of macular degeneration (Weikel 2012). A combination of vitamin A and omega-3 fatty acids may be helpful for individuals with retinitis pigmentosa; one study found rates of yearly vision decline were slower among subjects supplementing with vitamin A and consuming greater than 200 mg of omega-3’s than among those supplementing with vitamin A and consuming lower amounts of omega-3’s (Berson 2012).
  • Carotenoids: Higher carotenoid consumption, especially lutein, zeaxanthin, and meso-zeaxanthin, has been linked to better eye health, including a lower risk of macular degeneration and cataracts (Ma 2013; Nolan 2013; Hammond 1997).
  • Astaxanthin: Several Japanese studies reported that supplemental astaxanthin was associated with better visual acuity and significantly less visual fatigue (Kidd 2011).
  • Carnosine eye drops: In a study on adults with cataracts treated with eye drops containing carnosine for 3‒6 months, vision improvement was reported in all subjects with primary senile cataract and 80% of subjects with mature senile cataract (Wang 2000).

2 Introduction

Loss of vision is one of the most feared consequences of aging (Rosenberg 2008; AFB 2007). As of 2010, an estimated 1.28 million US adults over age 40 were blind and another 2.9 million had very poor vision; about 10% to 20% of adults aged 80 and older had poor vision. Common causes of blindness in adults include macular degeneration, cataracts, glaucoma, and diabetic retinopathy (NEI 2014; Congdon 2004).

Adults with poor vision are at a significantly higher risk for many social and health problems including depression, social withdrawal, and self-administered medication errors (Casten 2013; Rosenberg 2008; Rowe 2004; Campbell 2005; Field 2007). Elderly adults with low vision enter nursing homes about 3 years earlier and have twice the risk of falls compared to adults with adequate vision (Eichenbaum 2012). Poor vision can also limit freedom to drive; adults with impaired vision often must avoid driving at night, over long distances, or in unfamiliar conditions (Sengupta 2013). Vision loss can significantly impact quality of life and ability to function independently (CDC 2014; IFA 2014).

Fortunately, scientifically-studied integrative interventions and simple lifestyle measures can prevent, slow the development of, or even partially reverse many common eye diseases associated with aging. Nutrient interventions such as omega-3 fatty acids; carotenoids; vitamins A, B-complex, and E; and coenzyme Q10 (Chew 2013; Christen 2009; Christen 2008; Feher 2005; Weikel 2012) have been shown to support eye health with aging. In addition, lifestyle interventions such as exercise (Munch 2013), avoiding smoking (Velilla 2013), and limiting intake of refined sugars (Tan 2007) have been demonstrated to significantly reduce the risk of several types of age-associated eye disease.

This protocol focuses primarily on preventive measures aimed at maintaining generally healthy vision with aging. For more comprehensive discussions on prevention and treatment options tailored to specific eye diseases, see the protocols on Macular Degeneration, Retinopathy, Glaucoma, or Cataracts.​

3 Understanding the Eyes

Proper vision depends upon the health of a number of organs, including the eyes themselves, the muscles that support and move the eyes, the optic nerve, and various portions of the brain that sense and interpret visual input (Merck 2013).

The eye consists of the following parts (Merck 2013; Swartz 2014):

  • Sclera: Outer layer of the eye; it is fibrous and white in appearance, often referred to as the “white of the eye.”
  • Conjunctiva: Thin transparent membrane located in the front of the eye over the sclera.
  • Cornea: Dome-shaped region in the front-center of the eye through which light enters and is partially focused by the cornea.
  • Pupil: Central black dot of the eye through which light is transmitted.
  • Iris: Circular colored area of the eye which controls the size of the pupil in response to ambient light conditions (the iris connects to small muscles that dilate the pupil in response to dim light and constrict the pupil in response to bright light).
  • Lens: Situated behind the pupil, the lens refracts light and helps focus it on the part(s) of the eye that transmit visual stimuli to the brain; it can change its shape to allow for both near and far vision.
  • Vitreous Humor: Transparent, gel-like substance comprised largely of water that fills the cavernous inner part of the eye between the lens and the retina (Bishop 2000).
  • Eye Anatomy

    (WikiMedia Commons 2013)

    Retina: The retina is located at the back of the eye and contains special photoreceptor cells that convert light energy into chemical reactions and finally into electrical impulses, which are transported by the optic nerve. A photoreceptor-rich area near the center of the retina is known as the macula. While the macula comprises only about 3-5% of the area of the retina, this region of the retina is critical for image resolution. In contrast to the centrally-located macula, rich in cone cells and therefore best adapted for high acuity vision resolution, the rest of the peripheral retina has much poorer ability to detect images with high acuity (Yanoff 2011).

    The retina contains 2 types of photoreceptors called rods and cones. The rods are much more numerous than cones and are responsible for low-light vision, peripheral vision, and black and white vision. Cones are responsible for color vision and are grouped mostly in the center of the retina. In the photoreceptor cells, the light that enters the eye is converted into electrical nerve impulses, which enter the optic nerve, cross the optic chiasm, and travel to the back of the brain where they are interpreted (Merck 2013).

    Photoreceptor cells are protected against light damage by the macular pigments (lutein, zeaxanthin, and meso-zeaxanthin) (Krinsky 2003; Berg 2002). The macular pigments sit above the photoreceptor cells to absorb blue light and neutralize free radical chemicals (Yanoff 2011; Chucair 2007; Ehrlich 2008; Nolan 2013; Carpentier 2009; Krinsky 2003). Macular degeneration is characterized by a number of factors including reduced levels of retinal pigments and reduced blood flow to the macula (Ehrlich 2008; Ferri 2014).

Understanding Visual Acuity

Visual acuity is typically reported as one number over another number; for example, 20/20 is considered “normal” vision. The number is usually determined based upon an individual’s ability to read a Snellen chart (the chart in the eye doctor’s office with letters that decrease in size with each progressive line). But what exactly does this mean?

The first number in the ratio represents the individual’s distance in feet from the eye chart at which he or she can clearly read the letters. The second number represents the distance in feet at which a person with normal vision could read the chart.

So, a visual acuity rating of 20/40 means that an individual has to be 20 feet away from the chart to read lines that a person with normal vision could read from 40 feet away. Conversely, if a person’s vision is better than average, he/she might have a visual acuity rating of 20/10, meaning that individual can read the chart from a distance of 20 feet, but a person with normal vision would need to stand 10 feet from the chart to read it (A.D.A.M. 2013; AOA 2014a).

4 Types of Eye Problems

Major causes of low vision and blindness in the United States include macular degeneration, cataracts, glaucoma, and diabetic neuropathy. Serious vision loss can also be caused by inherited eye diseases, traumatic eye injuries, stroke, blockage of eye blood vessels, infection, and retinal detachment. Many people are affected by more than one cause of vision loss (NEI 2014; Congdon 2004; MedlinePlus 2014; Yanoff 2011; AOA 2014b).

Macular Degeneration

Macular degeneration involves loss of nerve function in the central portion of the retina or macula (AMDF 2014). People with macular degeneration experience a gradual loss of vision - especially in the central visual field. About 1.75 million people in the United States have macular degeneration - most of them over 50 years old with a peak incidence from age 75 to 80 (Eichenbaum 2012; Yorston 2006; Chiang 2013). Macular degeneration is the most common cause of blindness among adults of European descent (Coleman 2008). Macular degeneration involves a number of harmful (pathological) processes including: 1) formation of yellow deposits in the retina called drusen, 2) areas of retinal cell death or atrophy, and 3) leakage of blood or other fluids from fragile and newly formed blood vessels within the eye. About 80% of people with macular degeneration have the “dry” type in which cell death or atrophy is the predominant factor. “Wet” macular degeneration occurs when there is extensive leakage of blood or fluids from newly formed blood vessels in the eyes. While wet macular degeneration accounts for 20% of the total cases of macular degeneration, it accounts for 90% of the severe cases of macular degeneration (when vision is reduced to less than 20/200) (Eichenbaum 2012). More information and treatment strategies are outlined in the Macular Degeneration protocol.

Cataracts

Cataracts are caused when protein fibers in the lens undergo harmful changes that cause them to become cloudy and impair vision. Diabetics are more likely to experience cataracts since high blood sugar levels promote binding of sugars (glycation) to proteins in the eye lens (Stevens 1995; Gul 2009). This glycation causes the lens to become cloudy and blurs vision. About 20.5 million US adults have cataracts (Eichenbaum 2012). Factors that significantly increase risk for cataract development include diabetes; smoking; regular alcohol consumption; family history of cataracts; excess exposure to sunlight; certain occupational exposures like welding, glassblowing, and radiation; eye cancers; and trauma to the eye (Megbele 2012; Shah 1945; West 1995; Finzi 2005; Muhit 2004; Kase 2008; Graham 2012). More information and treatment strategies are outlined in the Cataracts protocol.

Glaucoma

Glaucoma typically involves a gradual increase in eye pressure, which causes damage to the optic nerve (Chiang 2013). People with glaucoma experience reduced vision, especially in the outer (peripheral) field of view. About 2.2 million US adults have glaucoma (Eichenbaum 2012).

About 90% of glaucoma cases are called open angle glaucoma and usually occur slowly and gradually. About 10% of glaucoma cases are closed angle glaucoma, which can cause rapid vision loss. Both open and closed angle glaucoma involve blockage of fluid flow out of the eye (Eichenbaum 2012). More information and treatment strategies are outlined in the Glaucoma protocol.

Diabetic Retinopathy

Diabetic retinopathy damages vision in persons with long-term type 1 or type 2 diabetes. About 2.5% of all US adults and 28.5% of diabetic adults have diabetic retinopathy (Zhang 2010).

Diabetic retinopathy involves damage to tiny blood vessels (capillaries), formation of advanced glycation end products (AGEs), oxidative damage to cells, and inflammation. Low oxygen levels (ischemia) can develop in the retina, leading to increases in inflammatory chemicals (such as vascular endothelial growth factor [VEGF], cytokines, and angiotensin II) and increases in blood pressure. The resultant damage to eye blood vessels can cause further ischemia and promote growth of new eye blood vessels (neovascularization) which can reduce vision (Bandello 2013). More information and treatment strategies are outlined in the Retinopathy protocol.

Inherited Diseases and Genetics

Although genetic factors can affect the incidence of many types of eye problems, people with certain genetic conditions are likely to experience moderate-to-severe vision loss sometime in their life. Inherited (genetic) eye conditions include retinitis pigmentosa, Leber’s hereditary optic neuropathy, and others. Worldwide prevalence of retinitis pigmentosa is about 1 in 4000 (Hamel 2006; Hartong 2006). Retinitis pigmentosa first causes night blindness, then progressive loss of the peripheral (outer) field of view during daytime, and may lead eventually to total blindness (Hamel 2006). Leber’s hereditary optic neuropathy is a rare condition caused by harmful mitochondrial DNA mutations. Leber’s hereditary optic neuropathy first causes central vision loss which can progress to blindness by early or middle adulthood (Puomila 2007).

Other Common Eye and Vision Concerns

Double vision. Double vision or diplopia is the perception of a single object as two duplicate objects. Diplopia can be caused by many problems including lens cataracts, corneal infections or scars, hormone problems (eg, Grave’s disease), diabetes, autoimmune diseases (eg, multiple sclerosis), stroke, brain tumors, brain trauma, and migraine headaches (Kim 2013; Krol 2014; Ponto 2013; van Dijk 2013; Subei 2012; Rathore 2002; Kaiser 1999; Galli 2012; MNT 2009; Myers 1951; Tachibana 2013; Bothun 2009; Fujikado 2006; Melen 1978; Hsieh 1989).

Night blindness. Night blindness involves a greatly impaired visual ability in low-light conditions. Night blindness has many causes including cataracts, use of certain drugs, vitamin A deficiency, and genetic problems (eg, retinitis pigmentosa) (Loeffler 2013).

Eye floaters. Eye floaters are small spots that appear in the field of vision. Floaters are relatively common and the majority are caused by age-related changes to the vitreous humor. However, floaters require immediate medical attention if there is sudden onset of new floaters. Immediate medical attention is especially important if they are accompanied by flashes of light or losses of peripheral vision, as these conditions may be due to retinal detachment. Most cases of floaters do not require treatment. In rare, severe cases that significantly impact vision, surgery that removes and replaces the vitreous may be considered (Mayo Clinic 2012).

Dry eyes. Tear production often declines with age (Furukawa 1978). Eyes can also often become dry in windy or arid conditions. Dry eyes can lead to itching and blurred vision. Artificial tears can often provide short-term relief for dry eyes (Yanoff 2011).

Eye fatigue. Eye fatigue commonly occurs after spending long hours looking at small objects; straining to see in dim light; or when driving or using a computer screen for long periods. Eye fatigue can be minimized by placing computer screens at the proper location (about 20-26 inches away from and just below eyes) and taking breaks from long-term computer screen viewing (AAO 2011; Agarwal 2013).

Infection. A number of bacteria, fungi, and viruses can infect the eye or related structures like the eyelid. Prompt medical attention with antibiotics and sometimes surgery are often required to successfully treat eye infections (Yanoff 2011).

Refractive Errors

Refractive errors are common and are due to problems in the structure and function of the cornea, lens, and shape of the eye. The 3 main types of refractive errors include (Resnikoff 2008; Merck 2013; NEI 2010):

  • Myopia (near-sightedness): difficulty seeing objects far away. In 2010, about 34.1 million US adults over age 40 had myopia (NEI 2014).
  • Hyperopia (far-sightedness): difficulty seeing objects close-up. In 2010, about 14.2 million US adults over age 40 had hyperopia (NEI 2014).
  • Astigmatism (blurry outer [peripheral] vision): Astigmatism is usually caused by an irregularly-shaped lens or cornea. In 2008 a study of 12 010 US adults reported that 36.2% of all adults over age 20 years have significant astigmatism in one or both eyes (Vitale 2008).

Most common refractive eye problems can be corrected by the use of eyeglasses or contact lenses. ​

5 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).​

6 Integrative Interventions

AREDS Formulations and Other Multi-nutrient Combinations

The large Age-Related Eye Disease Study (AREDS) treated over 4000 subjects (aged 50-85 years) with a supplement containing the following daily nutrients: 15 mg (25 000 IU) β-carotene, 500 mg vitamin C, 400 IU vitamin E, 80 mg zinc, and 2 mg copper. The analysis of 3640 adults (age 55-80 years) who were followed for an average of 6.3 years reported that consumption of this AREDS supplement was associated with a 25% reduced risk of developing advanced macular degeneration compared to subjects receiving placebo (AREDS 2001). Recent research has suggested that supplementation with the carotenoids lutein and zeaxanthin may also be helpful in preventing macular degeneration and other eye diseases. A study of adults aged 50-85 years who were taking the AREDS daily supplement reported that the risk of developing late macular degeneration was reduced by 18% in subjects taking the AREDS supplement with 10 mg lutein and 2 mg zeaxanthin (Chew 2013).

Mixture of omega-3 fatty acids, carnitine, and coenzyme Q10. Carnitine and coenzyme Q10 (CoQ10) play a critical role in energy-producing mitochondrial reactions, whereas omega-3 fatty acids are important for health of blood vessels and cell membranes within the eye. One study treated adults (55-70 years) with early macular degeneration with either a mixture of 100 mg acetyl-L-carnitine, 530 mg omega-3 fatty acids, and 10 mg CoQ10 (48 subjects) or placebo (53 subjects) twice daily. After 12 months of treatment, vision worsened in only 2% (1 of 48) of the participants in the treatment group compared to 17% (9 of 53) of the participants in the placebo group (Feher 2005).

Multi-nutrient combination. A 2007 study treated older adults (average age 76) whom had macular degeneration with a daily mixture of the following nutrients: 10 000 IU vitamin A, 18 640 IU β-carotene, 452 mg vitamin C, 200 IU vitamin E, 70 mg zinc oxide, 400 mg taurine, 1.6 mg copper, 180 mg eicosapentaenoic acid (EPA), 120 mg docosahexaenoic acid (DHA), 8 mg lutein, and 0.4 mg zeaxanthin. The subjects were compared to a placebo group. After 6 months of treatment, visual acuity improved significantly in the adults treated with the multi-faceted supplement program, while visual acuity declined significantly in the subjects given placebo (Cangemi 2007).

B-Vitamins

Regular use of B-complex vitamin supplements may also help maintain eye health and prevent buildup of the toxic metabolite homocysteine. A study of 5442 women aged ≥40 years at baseline were treated with either a daily supplement containing 2.5 mg folic acid, 50 mg vitamin B6, and 1 mg vitamin B12 or placebo. After an average 7.3-year follow-up period, the risk of developing macular degeneration was 33% lower in the group taking the supplement compared to placebo (Christen 2009). Adequate folate consumption is also important for eye health. In some individuals, supplementation with 5-methyltetrahydrofolate (5-MTHF) may be more efficient than supplementation with folic acid. Folic acid is converted into the active form of folate, 5-MTHF, via an enzymatic metabolic pathway (Pietrzik 2010). However, several common genetic mutations interfere with the effective metabolism of folic acid into 5-MTHF (Pietrzik 2010; Kirke 2004). Studies with pregnant women and adults with coronary artery disease reported that supplementation with 5-MTHF was associated with significantly higher levels of the active 5-MTHF in both blood serum and red blood cells (Willems 2004; Lamers 2006). In some cases, 5-MTHF supplementation was up to 7 times more effective in increasing blood plasma levels than folic acid (Willems 2004).

Other B-vitamins also play an important role in preventing cataracts. In one review, five of 8 published studies reported that increased riboflavin (B2) use was associated with a significantly lower risk of cataracts (Chiu, Taylor 2007). A cross-sectional study examined the use of supplemental B-vitamins and incidence of cataracts in 2873 Australian adults aged 49-97 years. Compared to adults who did not use B-vitamin supplements, the risk of cataracts was 30% lower in those who consumed at least 4.4 mg supplemental thiamine (B1) daily, 30% lower in those who took ≥6.8 mg riboflavin (B2) daily, and 50% lower in those who took ≥8 µg vitamin B12 daily (Kuzniarz 2001).

Use of benfotiamine (a fat-soluble form of vitamin B1) has been able to prevent experimentally induced diabetic retinopathy in preclinical research. Benfotiamine was found to inhibit several mechanisms implicated in high blood sugar-induced vascular damage, including inhibition of advanced glycation end products (AGEs) (Hammes 2003).

Omega-3 Fatty Acids

Consumption of omega-3 fatty acids has been shown in several studies to reduce risk of macular degeneration (Weikel 2012). Omega-3 fatty acids are found in higher concentrations in fatty fish/fish oils, evening primrose oil, and flax/flax oil. Fish-based omega-3 fatty acids consist largely of DHA and EPA while plant-based omega-3 fatty acids are primarily ALA (alpha [α]-linolenic acid) (Koh 2013; Weikel 2012).

Studies have revealed that higher consumption of omega-3 fatty acids is associated with significantly lower rates of macular degeneration and a significantly lower risk of progression to late macular degeneration (Weikel 2012). Higher fish intake was associated with significantly less progression to early and/or late macular degeneration in 4 of 6 studies (Weikel 2013). A 12-year study of 72 489 adults over age 50 years reported the risk of developing macular degeneration was reduced 30% in the highest versus the lowest groups of DHA consumption (Cho 2001). A 5-year study of 2335 adults over 49 years of age reported that consumption of fish at least once a week was associated with a 40% reduction in early macular degeneration risk, and consuming fish 3 or more times per week was associated with a 75% lower risk for late macular degeneration compared to subjects consuming fish less than once per week (Chua 2006).

Several studies have also reported that omega-3 fatty acids or fish oil can significantly reduce the symptoms of dry eye syndrome. A large double-blind study treated 325 patients with dry eyes with either an omega-3 supplement containing 325 mg EPA and 175 mg DHA or placebo twice daily for 3 months. After 3 months, 65% of the subjects who received omega-3 supplements reported significant improvement in dry eye symptoms compared to 33% of the placebo subjects (Bhargava 2013). Another study of 64 adults (age 45-90 years) with dry eye symptoms treated participants with either 180 mg EPA and 120 mg DHA twice daily for 30 days or 2 medium chain triglyceride oil capsules for 1 month. Subjects given the EPA-DHA supplement had significantly fewer dry eye symptoms and significantly more tear secretion compared to subjects given the medium chain triglycerides (Kangari 2013). Another study reported significantly fewer dry eye symptoms in 152 subjects given fish oil capsules containing 1245 mg EPA and 540 DHA daily compared to 15 subjects given placebo (Kawakita 2013).

Carotenoids

Carotenoids are phytochemicals found in a wide range of fruits and vegetables - especially those of dark green or yellow color. Higher carotenoid consumption has been linked to better eye health, including a lower risk of macular degeneration and cataracts. Lutein, zeaxanthin, and meso-zeaxanthin are considered to be especially helpful since they are the most common carotenoids found in the eye lens and retina (Ma 2013; Nolan 2013; Hammond 1997). Lutein, zeaxanthin, and meso-zeaxanthin absorb low wavelength light and minimize oxidative damage to the retina and other parts of the eye (Krinsky 2003). These carotenoids are found in especially high concentrations in the macula of the eye. Meso-zeaxanthin is the most common carotenoid in the center of the macula, zeaxanthin is the most common carotenoid in the middle periphery of the macula, and lutein is the most common carotenoid in the outer peripheral macula region. Meso-zeaxanthin is thought to be produced in the body from the phytochemical lutein (Nolan 2013). However, studies have reported that the ability to synthesize meso-zeaxanthin declines with age and macular levels of meso-zeaxanthin may fall considerably in older adults and smokers (Kirby 2010).

One study that included 3139 adults aged 60-79 years reported that those in the highest group of dietary consumption of lutein and zeaxanthin were 90% less likely to develop early changes associated with macular degeneration (eg, pigmentary abnormalities and age-related maculopathy) than those in the lowest consumption group (Mares-Perlman 2001). Several studies have reported that higher blood levels of lutein, zeaxanthin, or total carotenoids are associated with lower risk of cataracts (Weikel 2013). A study that included 1689 older adults (61 to 81 years old) reported that subjects with the highest blood lutein levels were 42% less likely to have nuclear cataracts (cataracts that affect the center of the lens) than those with the lowest levels. Subjects with the highest zeaxanthin blood levels had a 41% lower risk for nuclear cataracts (Karppi 2012). A comprehensive review of 6 studies involving close to 42 000 aging adults reported that higher dietary levels of lutein and zeaxanthin were associated with significantly lower rates of cataract formation (Ma 2013). The largest of these 6 studies involved 39 876 women with a follow-up period of 10 years. Women with the highest levels of lutein/zeaxanthin consumption (median daily intake of 6.7 mg) had an 18% lower risk of cataracts than those with the lowest levels of lutein/zeaxanthin consumption (median daily intake of 1.2 mg) (Christen 2008).

A double-blind study treated 36 adults (average age 51 years) with one of the following: lutein and zeaxanthin; lutein, zeaxanthin and meso-zeaxanthin; or placebo. At the end of the 6-month study, both visual acuity and contrast sensitivity (with and without glare) improved significantly only in the group given all 3 eye carotenoids (Loughman 2012). Another study of healthy adults reported that daily supplementation with meso-zeaxanthin, lutein, and zeaxanthin for 6 months resulted in significant increases in blood levels of lutein and zeaxanthin and an increase in the central macular pigment optical density compared to subjects given placebo (Connolly 2011).

Astaxanthin. Astaxanthin, another carotenoid, is a red-colored pigment produced by algae, bacteria, and fungi. It is present in algae-eating fish and shellfish and is found in especially high levels in red-colored seafood such as crab, lobster, krill, salmon, and shrimp. Astaxanthin has strong anti-inflammatory and anti-oxidative properties. Several Japanese studies reported that 6 mg daily of supplemental astaxanthin was associated with significantly better visual acuity and significantly less visual fatigue (Kidd 2011).

Alpha-carotene. Alpha-carotene is one of a family of plant-derived compounds known as carotenoids, a group that includes the better-known beta-carotene as well as lycopene. Like beta-carotene, alpha-carotene can be converted to vitamin A in the body (Higdon 2015). A growing body of research shows the importance of alpha-carotene for eye health. In one large study, more than 63 000 women and 38 000 men over the age of 50 were followed for 24–26 years. Subjects with the highest intake of alpha-carotene were 25–35% less likely to develop advanced AMD compared with those with the lowest intake; additionally, those with the highest intake of lutein plus zeaxanthin were found to have a 41% lower risk of developing advanced AMD during the study (Wu 2015).

Additional research suggests alpha-carotene may also protect against cataracts and glaucoma. In a study with 584 female African-American participants, those with the highest dietary intake of alpha-carotene were 55% less likely to have glaucoma than those with the lowest intake (Giaconi 2012). Having a higher level of alpha-carotene in the blood was found to be associated with lower incidence of cataract (Dherani 2008), and higher dietary intake of alpha-carotene was found to be correlated with lower risk of cataract opacities on the back of the lens in non-smoking women aged 53–73 (Taylor 2002).

Vitamins A, C, E, and D

Some studies have reported that higher consumption of the antioxidant vitamins A, C, and E (in diet or supplements) is associated with a significantly lower risk of many eye problems, especially cataracts. Vitamin C is an important antioxidant found in the lens and aqueous humor of the eye at concentrations at least 50-fold greater than in the blood plasma (Weikel 2013). In one review, eight of 15 published studies reported that higher vitamin C intake, supplement use, or blood levels were associated with significantly lower rates of nuclear cataracts (Chiu, Taylor 2007). Researchers noted that consuming ≥135 mg of vitamin C daily (food and supplements) was associated with an approximately 40% decreased risk of cataracts (Weikel 2013). Studies also report that higher consumption of vitamin E is associated with a significantly lower risk of cataracts (Chiu, Taylor 2007).

Several studies have reported that higher intake or higher blood levels of retinol or vitamin A are associated with a significantly lower risk of cataracts (Weikel 2013). One study reported that risk of cataracts was 58% lower in people who used vitamin A supplements and 46% lower in those who used vitamin D supplements compared to supplement nonusers (Klein 2008).

Lipoic Acid

Lipoic acid, a powerful antioxidant, is involved in many energy-producing reactions and may help control blood sugar in diabetics. In a double-blind study 38 adults with type-2 diabetes were randomly assigned to receive placebo or various doses of alpha-lipoic acid (300, 600, 900, and 1200 mg/day). After 6 months, all treatment groups showed significantly better blood sugar control compared to placebo: there was a dose-dependent decrease in fasting blood glucose levels (with maximal effect at 900 mg/day for blood glucose, but there was a further improvement in HbA1c for the 1200 mg dose). A similar dose response was seen for HbA1c with maximal effect at 1200 mg/day (Porasuphatana 2012). Supplemental lipoic acid significantly reduced both blood sugar levels and risk of cataracts in diabetic rats. The authors conclude, “Light-scattering measurements indicated that dietary LA [lipoic acid] is effective in delaying not only cataract development but also its progression. LA may be able to do this by preventing protein glycation and reducing oxidative stress…” (Kojima 2007). In a preclinical study, supplemental lipoic acid significantly increased tear production in a dry eye model (Andrade 2014). Human clinical trials involving lipoic acid supplementation and eye health are eagerly awaited.

Zinc

Concentrations of zinc are high in the retina (Weikel 2012). Zinc is involved in many processes involving immunity, reproduction, and nerve development. Several studies found that higher zinc intake was associated with a lower risk of macular degeneration or vision loss (Weikel 2012; Mares-Perlman 1996; van Leeuwen 2005; VandenLangenberg 1998; Tan 2008). A large study of 4170 adults reported that higher zinc and vitamin E intake was associated with a lower rate of early macular degeneration. This study also found an above-median intake of β-carotene, vitamins C and E, and zinc was associated with a 35% reduced risk of AMD (van Leeuwen 2005). One study of 80 macular degeneration subjects reported that supplementation with 25 mg zinc twice daily was associated with significantly better vision (Newsome 2008).

Carnosine Eye Drops

N-acetylcarnosine is a small molecule consisting of 2 amino acids. N-acetylcarnosine can be used topically as eye drops and easily reaches both the water soluble and fatty parts of the eye. (N-acetylcarnosine is metabolized to carnosine in the lipid area of the eye). Carnosine is a strong antioxidant and helps prevent glycation (glycation involves sugar binding to and damaging proteins in the body) of the eye tissue and other body tissues (Budzen 2013; Babizhayev 2009; Babizhayev 2012; Babizhayev 2010; Babizhayev, Khoroshilova-Maslova 2012). 

Several studies have reported beneficial effects of N-acetylcarnosine eye drops. A study treated 96 adults with cataracts with 1 or 2 drops of eye drops containing N-acetylcarnosine in each eye 3 or 4 times daily for 3-6 months. At the end of the treatment, vision improvement was reported in all subjects with primary senile cataract and 80% of subjects with mature senile cataract (Wang 2000). A double-blind study treated 147 adults that had cataracts and/or refractive errors with either eye drops containing 1% N-acetylcarnosine or placebo twice daily in each eye for 9 months. After 9 months, significantly better visual acuity and significantly lower glare problems were noted in the adults who received the N-acetylcarnosine eye drops compared to placebo. No significant side effects were seen in the N-acetylcarnosine treatment group (Babizhayev 2009).

Resveratrol

Resveratrol is an anti-inflammatory phytochemical found in grapes (especially dark-colored grapes), cranberries, other berries, Japanese knotweed, and peanuts (Baur 2006). Studies with cultured human cells have reported that resveratrol is protective against oxidative damage (Sheu 2013). Evidence from a small case series showed that 3 adults aged 75-88 years whom had severe visual loss from macular degeneration benefited from treatment with 100 mg of oral trans-resveratrol daily. All 3 subjects had been taking standard eye health supplements containing 15 mg β-carotene (a form of vitamin A), 500 mg vitamin C, 400 IU vitamin E, 80 mg zinc, and 2 mg copper. After 2-6 weeks of treatment with 100 mg trans-resveratrol daily, vision improved significantly in all 3 subjects (Richer 2013). Larger studies are needed to examine the potential beneficial effects of resveratrol supplementation on elderly people with macular degeneration.

Anthocyanins and C3G

Anthocyanins are water-soluble plant pigments found in dark-colored fruits and vegetables. Some of the richest sources of anthocyanins include chokecherries, black currants, wild blueberries, bilberries, blackberries, and red or purple grapes (Hosseinian 2007; Anisimoviene 2013; Flamini 2013; Wu 2006; Nile 2014; Mazza 2007; Jaakola 2010). During World War II, British pilots ate bilberry jam several hours before night missions to improve their night vision. Research findings on the night vision effects of bilberry or bilberry extracts have been mostly positive. Subjects in these studies generally received bilberry or bilberry extracts containing 12-40 mg of anthocyanins daily (Canter 2004). A 2-year study reported that 50 mg daily consumption of black currant anthocyanins was associated with a significant drop in eye pressure in patients with open-angle glaucoma compared to 19 people given placebo (Ohguro 2012). An experimental in vivo animal model revealed that the daily consumption of 1 mL of blueberry juice was protective against light-induced retinal damage (Tremblay 2013).

An anthocyanin of particular interest is cyanidin-3-glucoside or C3G. C3G has a wide range of health benefits including antioxidant, anti-inflammatory, and DNA-protecting effects (Ding 2006). C3G has been shown to selectively upregulate expression of genes that protect aging tissue, while downregulating genes that cause damage (such as pro-inflammatory cytokines) (Tsuda 2006; Sasaki 2007; Tsuda 2005). C3G helps protect the retina by several mechanisms and stimulates production of a retinal pigment called rhodopsin (Liu 2012; Matsumoto 2003; Tirupula 2009). Rhodopsin is a critical pigment for seeing in dim light. C3G also serves to protect retinal cells from harmful oxidation and free radical protection in the light (Jang 2005).

Ginkgo Biloba

A number of lab animal and cell culture studies have reported that Ginkgo biloba extracts have strong antioxidant as well as anti-inflammatory properties and provide protection against oxidative damage to retina cells and mitochondria in cells (Huynh 2013). A Korean study examined the effects of Ginkgo biloba extract in 30 adults with normal tension glaucoma (a form of glaucoma in which damage to the retina and optic nerve occur even in the presence of normal internal eye pressure). Subjects who received 80 mg of Ginkgo biloba extract twice daily for 4 weeks had significantly better retinal blood flow compared to subjects who received placebo (Park 2011). Two small human studies reported that supplementation with 80 mg twice daily or 240 mg once daily of Ginkgo biloba led to modest improvement in vision of individuals with macular degeneration (Evans 2013).

Curcumin

Curcumin is a major phytochemical constituent of the common Indian herb turmeric. Several studies reported that curcumin has many anti-inflammatory and anti-cancer properties (Huynh 2013). Preclinical studies have reported that curcumin supplements can slow progression of diabetic retinopathy and cataracts and help prevent formation of new blood vessels (neovascularization) in animal models of macular degeneration (Pescosolido 2013; Xie 2012). One clinical study treated adults with diabetic retinopathy with either 200 mg curcumin twice daily (39 subjects) or placebo (39 subjects). After 4 weeks of treatment, the subjects receiving curcumin had significantly less eye swelling (edema) and improved blood flow in the retina and other parts of the eye (Steigerwalt 2012).

Pycnogenol®

Pycnogenol®, a bark extract from the French Maritime Pine Pinus pinaster, has been shown to protect cells from oxidative damage (Bartlett 2008). In one study, subjects with diabetic or hypertensive retinopathy were treated with either 50 mg of Pycnogenol® or placebo three times daily for 60 days. Visual acuity improved significantly and retinopathy did not increase in subjects treated with Pycnogenol®. Visual acuity and retinopathy worsened in those receiving placebo. Eye blood vessel studies (fluorangiography) showed significant improvement in retinal blood vessels and reduction in eye membrane leakage in the Pycnogenol® but not the placebo group. This suggests that Pycnogenol® may support the structural integrity of delicate blood vessels in the eye (Spadea 2001). Another study of diabetic adults with moderate diabetic retinopathy reported that treatment with 50 mg Pycnogenol® three times daily (24 subjects) for 2 months showed significant improvement in visual acuity, eye blood flow, and reduced retinal edema (swelling) compared to placebo (22 subjects) (Steigerwalt 2009). Yet another study reported that treating people who had asymptomatic elevated eye pressure with 40 mg Pycnogenol® and 80 mg standard bilberry extract twice daily for 6 months significantly reduced eye pressure in 95% of subjects. A decrease in eye pressure was reported in only 5.5% of the placebo group (Steigerwalt 2008).

Taurine

Taurine is an amino acid that comprises almost half of the free amino acid content of the retina. Animal and tissue culture studies have reported that taurine supplements provide significant protection against retinal cell degeneration (Froger 2012). Supplemental taurine was found to be protective against retinal damage in experimental animal models with the taurine-depleting seizure medication vigabatrin (Sabril®) (Jammoul 2009).

Aristotelia chilensis Berry Extract

Aristoteliachilensis (A. chilensis) (Maqui or Chilean wineberry) is a berry-producing plant native to certain areas of South America, as well as parts of Asia, Australia, and the Pacific region (Schreckinger 2010; Romanucci 2016). Analysis of phytonutrients from A. chilensis has revealed high concentrations of anthocyanins including cyanidins and delphinidins, flavonol glycosides, and ellagic acids (Brauch 2016). Maqui berry is an especially rich source of delphinidins, a specific type of anthocyanin with powerful anti-inflammatory and free radical-quenching capacity, and other bioactive properties that include protection of blood vessels and protection against sun damage (Watson 2015).

Delphinidins extracted from A. chilensis have been demonstrated to protect photoreceptor cells in the retina of the eye from light-induced damage. This eye protecting effect was likely mediated by blocking the damaging effect of reactive oxygen species on sensitive retinal tissue (Tanaka, Kadekaru 2013).

In a rodent study, a maqui berry extract rich in delphinidins protected lacrimal gland (tear-forming) tissue from damage by suppressing reactive oxygen species and preserving tear formation and secretion (Nakamura 2014). In another study, people with moderately dry eyes consumed 30 or 60 mg A. chilensis berry extract for 60 days; a substantial improvement in tear fluid amount, compared with baseline, occurred within 30 days. Those in the 60 mg group experienced a more durable improvement, with a 45% increase in tear production compared with baseline, and substantial improvement in dry eye-related quality of life score, a patient-reported measure of eye function, comfort, and symptoms (Hitoe 2014).

Saffron Extract

Saffron (Crocus sativus) has been used for centuries as a culinary and medicinal herb. Its therapeutic effects on macular and visual health are likely related to the actions of its carotenoids, which include crocin, crocetin, and safranal (Alavizadeh 2014; Fernandez-Sanchez 2015; Higdon 2015). In laboratory and animal research, both crocin and crocetin have been found to protect retinal cells from damage due to light exposure, oxidative stress, and loss of blood flow (Fernandez-Sanchez 2015; Chen 2015), and crocin-related compounds have been found to increase retinal blood flow (Xuan 1999). In addition, safranal was found to protect retinal cells and prevent capillary loss in an animal model of retinitis pigmentosa (Fernandez-Sanchez 2012). 

Research has found saffron may help prevent AMD, suggesting it might play a valuable role as an eye protectant and in restoring vision. In a randomized, controlled, crossover clinical trial of saffron effect on AMD, 25 subjects with early AMD received either 20 mg per day of saffron or placebo. Retinal light sensitivity, a marker of macular health, improved with saffron but not placebo (Falsini 2010). To evaluate the long-term benefits of saffron supplementation, 29 subjects with early AMD took 20 mg saffron daily for an average of 14 months. Retinal sensitivity improved after the first three months of treatment. In addition, at the three-month exam, visual acuity improved such that subjects could accurately read, on average, two more lines on the standard vision test than they could prior to treatment. These changes were sustained for the duration of the study (Piccardi 2012). A third study, in which 33 patients with early AMD took 20 mg saffron per day for an average of 11 months, found retinal sensitivity improved in those taking saffron whether or not they had a genetic vulnerability to AMD (Marangoni 2013).

Saffron may have a general protective effect on eye health, preventing other conditions as well. In a randomized clinical trial, 34 patients with open-angle glaucoma received either 30 mg per day saffron extract or placebo, in addition to usual treatment, for one month. Saffron treatment resulted in greater reductions in intraocular pressures than placebo (Jabbarpoor Bonyadi 2014). In animal research, treatment with saffron extract prevented experimentally-induced and diabetes-related cataract formation. In a study in diabetic animals, saffron extract decreased AGEs and serum glucose levels (Makri 2013; Bahmani 2016). Saffron treatment was also found to prevent retinal damage in a mouse model of Parkinson disease (Purushothuman 2013).

Integrative Interventions for Retinitis Pigmentosa and Leber’s Hereditary Optic Neuropathy 

Vitamin A and omega-3 fatty acids appear to be potentially beneficial for individuals with retinitis pigmentosa. A study enrolled 601 adults (aged 18-49 years) with retinitis pigmentosa into one of 4 groups to receive the following daily: 15 000 IU vitamin A; 400 IU vitamin E; both supplements; or neither supplement. The subjects receiving vitamin A had a 32% decreased risk of their visual acuity declining by half in a given year compared to those not receiving vitamin A (Berson 1993). Another analysis reported that among 357 adults with retinitis pigmentosa who received 15 000 IU vitamin A daily for 4-6 years, rates of vision decline were 41% slower per year in subjects receiving at least 200 mg omega-3 fatty acids daily (Berson 2012).

A human study treated 62 retinitis pigmentosa subjects with either a daily supplement of 1 g taurine, 400 mg vitamin E, and 30 mg of diltiazem (Cardizem®) (a drug used to treat high blood pressure) or placebo for 3 years. The retinitis pigmentosa subjects who received the taurine, vitamin E, and diltiazem had significantly better changes in vision compared to placebo subjects. Over the 3-year study, peripheral (outer) visual acuity declined significantly in 69% of the placebo subjects but declined only 6% in the treated subjects (Pasantes-Morales 2002).

Supplemental CoQ10, L-carnitine, B-vitamins, and the amino acids creatine and arginine have been useful for some people with mitochondrial disorders. These nutrients present a potential treatment for Leber’s hereditary optic neuropathy and other vision diseases linked to mitochondrial genes (Parikh 2009). 

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