In many eyecare practices, as many as one out of two adolescent patients have myopia.1 Gaining expertise in proactively managing myopia will benefit many of your patients.
Although the foundation of myopia control is soft contact lenses, orthokeratology (ortho-K), low-dose atropine, or novel spectacle designs, reviewing evidence-based lifestyle modifications is essential to a comprehensive myopia treatment plan.
Lifestyle modifications show the eyecare provider is interested in the complete approach and not just a certain product. Reviewing all beneficial options helps build trust, the critical element for long-term success.
The role of nutrition in myopia management
Consider a clinical scenario: It’s about 3:30pm on a Thursday afternoon, you’ve just finished a myopia control consult for a 9-year-old with a -2.25 prescription. The parents and the child are excited about your recommended treatment plan.
Then you hear, “What else can we do to help?” Enter lifestyle considerations. Lifestyle modifications are the most prescribed type of myopia management,2 even though their effectiveness is generally lower than other treatment options.
Within lifestyle modifications, near work and outdoor time have been researched extensively,1 but what nutritional theories might help prevent or slow the progression of myopia?
A clinician’s interest in nutrition demonstrates a commitment to overall health and its effect on ocular health. Two nutrition theories associated with myopia are oxidative stress and hyperinsulinemia.3,4 Daily food choices have direct effects on oxidative stress and insulin levels.
To read more about the role of nutrition in ocular health, check out A Guide to Dry Eye and Ocular Health Nutraceuticals with Download!
Oxidative stress and ocular health
Oxidative stress is a condition where the body has too many free radicals and not enough antioxidants. Free radicals have a bad reputation, but they are byproducts of normal metabolism. The problem comes when excess free radicals contribute to tissue damage and a variety of systemic and ocular diseases.
In the eye, oxidative stress is associated with the pathogenesis of keratoconus, corneal dystrophies, glaucoma, macular degeneration, and myopia.5,6 Specific to myopia, eyes with high myopia have chemical indicators of higher free radicals and lower total antioxidant capacity. Nitrite levels are a marker for oxidative stress in the body.
Merida et al. show that total nitrite levels are significantly higher in eyes with high myopia compared to eyes with low myopia or hyperopia.3 They also show that total antioxidant capacity (TAC) in eyes with myopia and high myopia is lower than in eyes with emmetropia or hyperopia. Low TAC is another indicator of oxidative stress.
Oxidative stress within the eye contributes to corneal disease and posterior segment disease. The high level of free radicals present in eyes with high myopia may explain some of the pathology associated with high myopia, specifically glaucoma is more prevalent in high myopia and oxidative stress plays a role in the pathophysiology of glaucoma.6 Merida et al.’s study involved elderly adults and showed that oxidative stress is higher in eyes with longer axial lengths.
Vutipongsatorn et al. showed that lowering oxidative stress helps reduce myopia progression by suppressing chronic scleritis.7 From what we currently understand, lowering oxidative stress may reduce axial elongation and the risk of ocular pathology.
Considering glycemic index with dietary choices
Some nutritional factors that increase oxidative stress are foods with a high glycemic index and excessive caloric intake.
Table 1: Recommended daily caloric intake by age.8
| Age | Male | Female | ||
|---|---|---|---|---|
| Sedentary | Active | Sedentary | Active | |
| 2 | 1,000 | 1,000 | 1,000 | 1,000 |
| 3 | 1,000 | 1,400 | 1,000 | 1,200 |
| 4 to 5 | 1,200 | 1,400 | 1,200 | 1,400 |
| 6 | 1,400 | 1,600 | 1,200 | 1,400 |
| 7 | 1,400 | 1,600 | 1,200 | 1,600 |
| 8 | 1,400 | 1,600 | 1,400 | 1,600 |
| 9 | 1,600 | 1,800 | 1,400 | 1,600 |
| 10 | 1,600 | 1,800 | 1,400 | 1,800 |
| 11 | 1,800 | 2,000 | 1,600 | 1,800 |
| 12 | 1,800 | 2,200 | 1,600 | 2,000 |
| 13 | 2,000 | 2,200 | 1,600 | 2,000 |
| 14 | 2,000 | 2,400 | 1,800 | 2,000 |
| 15 | 2,200 | 2,600 | 1,800 | 2,000 |
Table 1: Courtesy of Faizan et al.
These values are averages and can serve as a guide with individual adaptation. Excessive caloric intake has been defined as > 200 calories/day above the recommended level.9
The higher the glycemic index the more a food acts like pure glucose in the body. Sugary beverages, candy, highly processed carbohydrate foods like cookies, high sugar breakfast cereals, and bagels are a few examples of high glycemic foods. One research group has called the modern lifestyle a “constant postprandial state,” which leads to chronic oxidative stress.10
Avoiding excessive caloric intake and high glycemic foods can lower oxidative stress by lowering the amount of circulating free radicals. In addition, increasing antioxidant consumption can lower oxidative stress.11
Foods that affect myopia risk and progression
With that background on the risks of chronic oxidative stress, lets review some specific ingredients / foods that may increase the risk for myopia.
High glycemic index foods
Female students who consumed one or more sugary beverages per day were reported to have a 1.8 times higher risk of myopia.12 Similarly, female students in France who consumed more refined carbohydrates had a significantly higher risk for myopia.13 A review of the United States National Health and Nutrition Survey also found that increased insulin levels were significantly associated with increased odds of having myopia.4
Chronic consumption of refined carbohydrates leads to higher insulin levels, which, over time, can lead to insulin resistance. As mentioned previously, a diet high in refined carbohydrates increases oxidative stress, which also leads to insulin resistance.10
Myopia is a multifactorial disease, and hyperinsulinemia may be one factor that contributes to the worsening of myopia. Two research groups postulate that high insulin levels increase axial length by the promotion of insulin-like growth factor-1, a hormone that regulates growth in the body.14,15
Vitamin D
Because outdoor time is tightly connected to vitamin D levels, some wondered if vitamin D supplementation could help protect or slow myopia. Some research has found a protective association between vitamin D levels and myopia.16
However, after controlling for the effect of outdoor time, several other studies have failed to find a link between low vitamin D levels and myopia.4
Sodium
Ronald B. Brown, PhD, proposes that increased sodium chloride consumption increases fluid retention causing fluid to flow into the vitreous, which creates a stretching effect on ocular tissue during axial elongation.17 Dr. Brown’s theory is based on the increasing prevalence in myopia and in dietary sodium intake over the past 50 years.
While it's true both sodium intake and myopia rates have increased, a causative association has not been shown and Dr. Brown concluded a very-low salt diet clinical trial is needed to test this theory.
Omega-3
Omega-3 supplementation has been shown to enhance antioxidant defense against free radicals and lower oxidative stress.18 In addition, higher levels of omega-3 are associated with more positive spherical equivalent refraction (lower risk of myopia) and show a trend with shorter axial length, although the statistical significance was not as strong.
This suggests omega-3 may be protective for myopia, although randomized clinical trials would be required to understand the dose, duration, and confirm the effectiveness of omega-3.19
Caffeine
Before reviewing the data on caffeine intake, let me just say, good luck to providers brave enough to consider recommending caffeine intake as a myopia treatment for an active 7-year-old.
Rest assured, instead of caffeine eye drops or beverages, it’s a metabolite of caffeine called 7-methylxanthine (7-MX) that has shown the ability to slow myopia progression. When taken orally in pill form, 7-MX slowed axial elongation by 0.17mm over 6 years. 7-MX is currently only used in Denmark.20
Foods with benefits for myopia
What are some kid-friendly foods that put all of this information together? Tangerines, apricots, blackberries, mangoes, and grapes are just a few foods with both antioxidant benefits and ones kids will happily eat. Watermelon, corn, peas, almonds, and our eyecare-favorite leafy greens are a few more. Follow this link for a more complete list.21
A berry smoothie is a great way to get an antioxidant boost while mixing in some other foods that kids have a harder time eating on their own. Use a low-sugar base liquid like water or almond milk to avoid a high glycemic load.
Key ingredients to increase the nutritional value of smoothies:21,22
- Greek yogurt to increase the protein
- Spinach leaves for lutein
- Avocado for vitamin E
- Chia seeds for omega-3
- Almonds for manganese and vitamin E
When reviewing nutrition, be sensitive to household needs and culture. It’s good to be suggestive and inquire gently to avoid offending parents. Every parent has good intentions, but the demands of a busy day or picky eaters are real.
Look for good things to praise about current habits and suggest a few specific changes. Like any treatment plan, create a goal, document it, and follow up at myopia progress checks.
Final thoughts
In conclusion, the strongest evidence for a dietary link between nutrition and myopia is high insulin levels and oxidative stress. Providing nutritional advice to parents and children regarding ways to lower the risk of insulin resistance and oxidative stress shows a comprehensive perspective and care for the child.
In conjunction with high efficacy treatments like ortho-K, soft multifocal contacts, peripheral defocus spectacles, or low-dose atropine, dietary changes and lifestyle modifications provide supplemental help in proactive myopia management.
