According to Food Navigator.com Full fat helps carotenoid absorption. According to the article:

Recent studies on carotenoids, used extensively in the food industry as a colouring agent, show that these antioxidants may reduce the risk of degenerative diseases, such as age-related macular degeneration. They are also linked to a preventative effect on heart disease and certain cancers.

The study was published in the August 2004 issue of the American Journal of Clinical Nutrition.

"Essentially no absorption of carotenoids was observed when salads with fat-free salad dressing were consumed. A substantially greater absorption of carotenoids was observed when salads were consumed with full-fat than with reduced-fat salad dressing."

The Cairo Dining web site reports that eating greens may save your eyesight.

Eating greens may also save your eyesight, thanks to their two carotenoids, lutein and zeaxanthin. This antioxidant combo decreases your risk for age-related macular degeneration. "Greens are packed with carotenoids because they sit out in the sun all day, so they need protection from sun-induced damage," says biochemist Dean P. Jones, PhD, of Emory University School of Medicine. "The carotenoids accumulate in the retina and protect your eyes." Dietary guidelines advise at least three cups of greens a week. Frozen or bagged is as good as fresh. 

Be sure to use some full fat dressing on that salad to get the maximum benefit OR you may choose to add an avocado to that salad for a nutrient boost!  Adding avocado to your salad can help you absorb up to 5 times more lutein!  Plus, a medium avocado contains about 66% of your daily folate requirement.