A significant amount of research over the years has indicated that reduced dietary intake of lutein is an important risk factor for the development of AMD. Additional clinical trials involving supplementation with lutein have shown benefits on a number of parameters of visual function.

A recent double-blind, placebo-controlled trial conducted in Austria (known as LISA, or Lutein Intervention Study Austria) assessed the effect of lutein supplementation or placebo on macularpigment optical density (MPOD) in 126 subjects with a diagnosis of AMD. After six

months of supplementation, the lutein group saw a statistically significant increase in MPOD (by an

average of almost 28%) versus placebo. There was also a significant correlation between lutein

supplementation and improved macular function and visual acuity after six months.

A randomized controlled trial research Optometry evaluated the effects of one year of relatively

high-dose zeaxanthin supplementation (8 mg) with and without lutein (9 mg), compared to the effects of lutein alone, in 60 individuals with mild to moderate AMD. The researchers found that MPOD increased similarly in both the lutein and zeaxanthin groups. In addition, the zeaxanthin group showed improvements in detailed high-contrast visual acuity and sharpened ability to discriminate shapes. Furthermore, a larger percentage of participants in this group experienced clearing of central scotomas (retinal areas with reduced light sensitivity that are common in individuals with AMD). The lutein group, on the other hand, experienced greater improvements in low-contrast visual acuity, enhanced contrast sensitivity, and improved glare recovery.

While there was significant overlap between the effects of lutein or zeaxanthin alone, the researchers’ findings indicated that zeaxanthin had greater benefits for cone-based visual function, and lutein improved rod-based visual function, thus indicating the complementary nature of both carotenoids.