Antioxidants key to lowering risk of age-related cataracts

A $5.7 billion global medical bill to restore sight for the estimated 45 million people with cataracts could be slashed in half by a diet rich in colorful fruits and vegetables, according to an international study.

Researchers from China and the University of South Australia have published the first study of its kind to verify the link between foods high in antioxidants and a lower risk of age-related cataracts (ARC).

UniSA Senior Research Fellow Dr. Ming Li and colleagues from Xi’an Jiaotong University analyzed 20 studies from around the world looking at the impact of vitamins and carotenoids on cataract risk.

Despite some inconsistencies, the findings overwhelmingly support the benefits of eating citrus fruits, capsicum, carrots, tomatoes and dark green vegetables such as spinach, broccoli and kale to delay the onset of ARC.

Their paper has been published in the American Journal of Clinical Nutrition ahead of World Optometry Week (March 26-30).

“Age-related cataracts are the leading cause of visual impairment among the elderly throughout the world, with unoperated cataracts contributing to 35 percent of all blindness,” Dr. Li says. “Although cataract extraction surgery is an effective method to restore vision, it will have cost society more than $5.7 billion by 2020.”

With the population aging dramatically and an increasing number of people needing surgery, urgent action is needed, the researchers say.

“If we could delay the onset of ARC by 10 years it could halve the number of people requiring surgery.”

Improvements would rely on global changes to most of the world’s diet, however, with current consumption of antioxidants well below the recommended level to prevent age-related cataracts.



A study has found that CBD — a major chemical component in marijuana — appears to increase the pressure inside the eye of mice, suggesting the use of the substance in the treatment of glaucoma may actually worsen the condition.


One of the most commonly proposed uses of medical marijuana is to treat glaucoma.

But a study from researchers at Indiana University has found that a major chemical component in the substance appears to worsen the primary underpinning of the disease: a rise in pressure inside the eye.

The chemical that causes this rise in pressure is cannabidiol, or CBD, a non-psychoactive ingredient in cannabis that is increasingly marketed to consumers in products such as oil, gummies, creams and health food. It is also approved in many states as a treatment for conditions such as pediatric epilepsy.

The study was reported Dec. 14 in the journal Investigative Ophthalmology & Visual Science.

“This study raises important questions about the relationship between the primary ingredients in cannabis and their effect on the eye,” said Alex Straiker, an associate scientist in the IU Bloomington College of Arts and Sciences’ Department of Psychological and Brain Sciences, who led the study. “It also suggests the need to understand more about the potential undesirable side effects of CBD, especially due to its use in children.”

The study, which was conducted in mice, specifically found that CBD caused an increase in pressure inside the eye of 18 percent for at least four hours after use.

Tetrahydrocannabinol, or THC, the primary psychoactive ingredient of marijuana, was found to effectively lower pressure in the eye, as has been previously reported. But the study found that the use of CBD in combination with THC blocked this effect.

Specifically, the study found that male mice experienced a drop in eye pressure of nearly 30 percent eight hours after exposure to THC alone. A lower pressure drop of 22 percent was also observed after four hours in male mice.

The effect was weaker in female mice. This group experienced a pressure drop of only 17 percent after four hours. No difference in eye pressure was measured after eight hours.

The results suggest that females may be less affected by THC, though it isn’t clear whether this extends to the substance’s psychoactive effects.

“This difference between males and females — and the fact that CBD seems to worsen eye pressure, the primary risk factor for glaucoma — are both important aspects of this study,” Straiker said. “It’s also notable that CBD appears to actively oppose the beneficial effects of THC.”

By comparing the effect of these substances on mice without specific neuroreceptors affected by THC and CBD, the IU researchers were also able to identify the two specific neuroreceptors — named CB1 and GPR18 — by which the first substance lowered pressure inside the eye.

“There were studies over 45 years ago that found evidence that THC lowers pressure inside the eye, but no one’s ever identified the specific neuroreceptors involved in the process until this study,” Straiker said. “These results could have important implications for future research on the use of cannabis as a therapy for intraocular pressure.”


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Supplementation Enhances Vision of Pre and Post Cataract Surgery Patients

By Mihir Parikh, MD

When vision is restored with successful cataract surgery and intraocular lens implantation, patients generally expect to have good vision for the rest of their lives. However, population studies do not necessarily support that assumption. A leading cause of permanent vision loss in the developed world is age-related macular degeneration (AMD), and the risk of AMD increases with advancing age. The elevated risk of AMD over time, coupled with longer life expectancy in the developed world, results in more years of life post cataract surgery. Thus, good vision throughout life may not be a foregone conclusion.

The Importance of Macular Function
AMD damages central vision because it affects the macular anatomy, and the loss of central vision can greatly affect a patient’s life. Physicians typically advise patients to control diabetes, blood pressure, and cholesterol to help maintain macular health. In addition, they often recommend smoking cessation, regular exercise, and eating a nutrient-dense, balanced diet. Yet, eyecare professionals should be providing a better explanation of the disease process and making more meaningful recommendations.

Recent Research
Published data suggests that the level of pigment found in the macula impacts the function of central vision and is associated with its ability to maintain a healthy state. The three pigments naturally found in the macula are lutein (L), zeaxanthin (Z), and meso-zeaxanthin (MZ). The function of these pigments is to filter short wavelength light and protect the macula from undergoing oxidative changes. Filtering short wavelength light (blue light) improves contrast sensitivity and visual function in low light and high light scatter conditions. Neutralizing oxidative changes to the deeper layers of the retina slows the inflammatory cascade, which is responsible for triggering the AMD process. Thus, it is advantageous to optimize the macular pigment density in the retina for all patients, but especially as part of ongoing treatment post cataract surgery.

The Central Retinal Enrichment Supplementation Trials (CREST) demonstrated in a double-blind, placebo-controlled, randomized trial that supplementing macular pigment in normal subjects with low macular pigment level increases contrast sensitivity.4 All three macular pigments were supplemented at a MZ:L:Z ratio of 10mg:10mg:2mg over a 12-month study period. Furthermore, a second trial in the CREST studies followed non-advanced AMD subjects given an AREDS2 formulation supplemented with meso-zeaxanthin also at the MZ:L:Z 10:10:2-mg ratio compared with subjects given the AREDS 2 formulation without MZ. In this double-blind, randomized, controlled trial over a 2-year period, supplementing with all three macular pigments (10:10:2-mg ratio) naturally found in the macula, the non-advanced AMD patients showed statistically significant improvement in contrast sensitivity, less glare, faster photo-stress recovery, and improved reading speeds.5 The findings of both studies demonstrate that replenishing all three macular pigments improved central vision in normal patients and those with early AMD.

Vision For Life
Recommending nutritional supplementation to maintain, optimize, and protect vision should be an important consideration for all cataract and refractive lens exchange patients. Vision for life starts before cataract surgery and continues for a lifetime.


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