Should I take those “eye vitamins”?
Do carrots really make my eyesight better?
What can I eat to prevent macular degeneration?
Such questions are common in the primary care setting. Flooded with an array of supplements at any pharmacy or grocery store, patients are justified in wondering which supplements might benefit their ocular health—or if any supplementation is needed at all. In most cases, the answer is far from straightforward, but supplements represent a modifiable risk factor in ocular conditions that often have a genetic component.
Macular Degeneration
The Trials
The Age-Related Eye Disease Study (AREDS) and the Age-Related Eye Disease Study 2 (AREDS2) are two of the largest and most rigorous clinical trials that have investigated the effects of nutritional supplementation on the progression of dry age-related macular degeneration (AMD) to wet AMD. Observational trials also have assessed the impact of diet and supplements on the development and progression of AMD.
The Results
- Patients without AMD did not benefit from taking the AREDS formulation.
- Patients with mild or borderline AMD did not benefit from taking either the AREDS or AREDS2 formulation.
- Both the AREDS and AREDS2 formulations slightly lowered the risk for AMD progression in those patients with intermediate or advanced AMD.
- Patients who smoke should take the AREDS2 formulation to avoid the beta-carotene in the AREDS formulation, which can increase the risk for lung cancer.
- Lutein, zeaxanthin, and omega-3 fatty acids were included in the AREDS2 formulation but did not decrease the risk for AMD progression (Figure).
- The Blue Mountains Eye Study found that the consumption of vegetables and dietary lutein and zeaxanthin was associated with a reduced risk for AMD.
The Conversation
- Patients with intermediate or advanced AMD should be encouraged to take the AREDS or AREDS2 formulation as a nutritional supplement.
- Smoking is a risk factor for the development and progression of AMD and should be discouraged.
- Physical activity should be encouraged, as it has been demonstrated to have a modest protective effect.
- A diet consisting of fish, fruits, leafy greens, and nuts has been shown to be beneficial in some studies.
Cataracts
The Trials
AREDS also addressed the benefits of antioxidants on cataracts but in an observational rather than an interventional way. The cross-sectional Blue Mountains Eye Study investigated the relationship between cataracts and supplements via a patient questionnaire. The Physicians’ Health Study was a longitudinal study that also assessed the relationship between cataracts and supplements. The Beaver Dam Eye Study reported on the relationship between the 5-year incidence of cataracts and supplements.
The Results
- One observational trial that included only women identified a healthy diet as being associated with a lower risk for cataract development
- Lutein, zeaxanthin, and B vitamins may decrease the risk for cataracts.
- Large, randomized trials found no benefit to taking vitamins C and E, beta-carotene, or selenium.
- The results are mixed regarding the potential benefit of a multivitamin.
- Sunlight exposure likely plays a role in the pathogenesis of cataracts, although knowledge of their exact pathogenesis is not fully understood.
The Conversation
- Cataract surgery is the only treatment for cataracts.
- No therapy has been proven to prevent or slow the progression of cataracts.
- Wearing sunglasses may protect against ultraviolet light exposure that can damage the lens.
- Recommending a multivitamin is probably appropriate, as it may be beneficial and is without adverse effects.
- Smoking increases the risk of developing cataracts, and patients who smoke should be encouraged to quit.
- Controlling systemic conditions, such as diabetes and hypertension, may not directly impact the development of cataracts but does help make patients better surgical candidates.