Abstract
Purpose: :
No study investigating the effect of macular pigment (MP) on visual performance has emphasized or evaluated the potential role of meso-zeaxanthin (MZ). Aside from its obvious protective function, MZ is somewhat intriguing from a visual performance perspective for a number of reasons including its dominance at the central macula and its capacity to extend the range of blue light filtration at the macula.
Methods: :
Thirty six subjects were recruited into this single blind, randomised and placebo controlled trial. Twelve subjects were randomly assigned to one of three supplementation groups. Group 1 were supplemented with a product containing 20 mg lutein (L) & 2 mg zeaxanthin (Z), Group 2 were supplemented with a product containing 10mg meso-zeaxanthin (MZ); 10mg L & 2 mg Z, while Group 3 were supplemented with placebo. Visual performance was assessed using a range of tests including: visual acuity, contrast sensitivity, glare disability, photostress recovery, ocular straylight, ocular discomfort rating and visual experience by questionnaire. MP, across its full spatial profile, was measured using the Macular Dentitometer TM. The full range of assessments was conducted, for each subject, on three separate visits, at baseline, three months and six months.
Results: :
At baseline, there were no significant differences, for any study parameters, between the three study groups (p > 0.05 for all). The only significant increase in MP was achieved in Group 2, and significance was reached by the 3 month visit (p = 0.002 to 0.035 across retinal eccentricities) and maintained at 6 months (p = 0.012 to 0.041 across retinal eccentricities). Statistically significant improvements in visual performance were observed across measures of visual acuity (p = 0.01), contrast sensitivity (p = 0.008 to 0.025 across spatial frequencies) and glare disability (p = 0.023 to 0.043 across spatial frequencies), but only in Group 2.
Conclusions: :
This study was designed to investigate the potential of two distinct MP supplements (in comparison to a placebo product), one containing MZ, one not containing MZ, and both with the same overall carotenoid content (22mg) to (a) augment MPOD and (b) enhance visual performance. The data show that vision in people with no occurring eye disease (i.e. normal healthy vision) can be improved if MP is significantly increased as was achieved in Group 2. The lack of any significant increase in MP or visual performance in either of the other two supplementation groups suggests, perhaps, that supplementation with all three macular carotenoids, including MZ, maximises the benefit of supplementation in terms of augmentation of MP and consequential improvements in vision.
Keywords: macular pigment • visual acuity • contrast sensitivity