BLOG: CREST results, Report 1

In the past 10 to 12 years, clinicians have increasingly been prescribing the macular carotenoids in supplement form to stop progression of age-related macular degeneration or as a preventive measure for those at risk of AMD.

Studies have shown that macular pigment selectively filters blue wavelength light and has powerful antioxidant properties. Considering that cumulative lifetime exposure to blue light causes oxidative stress in susceptible individuals and contributes to AMD, supplementation makes sense.

Dietary intake of lutein (L), zeaxanthin (Z) and, by some reports, mesozeaxanthin (MZ) leads to uptake into the blood serum and deposition in the macula. However, these carotenoids are in esterified form in the foods we eat, and our bodies must break down these foods to release these carotenoids into free form for absorption. And it doesn’t help that the typical western diet is lacking in the fruits, vegetables, eggs, and fish that contain L, Z and MZ. So, again, supplementation makes sense.

But let’s take a step back. AMD is a disease that we don’t see manifest until someone is in their 70s, or perhaps late 60. Yet human life expectancy even a century ago was much lower than this. Considering that out of 600 carotenoids found in nature, 50 are found in our diet, 15 make it into our blood serum, but only L, Z and MZ collect in the macula. Perhaps macular pigment serves a greater purpose than AMD prevention?

This is the question that the Central Retinal Enrichment Supplementation Trials (CREST) has set out to answer.

Chromatic aberration is the result of myopically defocused short wavelength blue light in the eye. Macular pigment is a potent blue light filter and is positioned prereceptorally, meaning it attenuates blue light before it reaches the tightly packed medium and long wavelength cones in the macula that are primarily responsible for visual acuity. The CREST study sought to investigate whether supplementing healthy individuals older than 18 years with low macular pigment levels with L, Z and MZ would improve visual function.

One hundred and five subjects were enrolled in the trial, with 53 receiving 10 mg L, 2 mg Z and 10 mg MZ (active group). The remaining 52 subjects received placebo. The primary outcome measure was increased contrast sensitivity (CS).

“Compared to placebo, statistically significant improvements from baseline CS were detected at 6 cycles per degree (P = 0.002) and 1.2 cycles per degree (P = 0.004) in the active group,” the researchers wrote. “Additionally, improvements in CS were commensurate with the observed increases in retinal concentrations of these carotenoids.”

While visual acuity is a measure of how small of an object we can resolve, CS measures how faint of an object we can resolve regardless of size. The conclusions drawn from this study are that enhancing macular pigment density with carotenoid supplementation can have meaningful effects on visual function in otherwise healthy eyes. In other words, it is appropriate and beneficial to prescribe supplements in the absence of eye disease such as AMD.

Put in perspective regarding patients we see in practice every day, improving CS may allow for better athletic performance in terms of seeing a ball faster. While driving, one might see an animal or child in the shadows along the road quicker. It could even help with the split second decisions a police officer or soldier may have to make, such as weapon or phone, sniper or villager.

As a profession, I believe we can do better than just improving visual acuity. Discussing ways to improve our patients’ overall visual experience is within our realm and, I would argue, our responsibility.

Reference:

Nolan JM et, al. IOVS. 2016;57(7):3429-3439. doi:10.1167/iovs.16-19520.