title: Central Retinal Enrichment Supplementation Trials (CREST): design and methodology of the CREST randomized controlled trials.
abstract: OBJECTIVE
  The Central Retinal Enrichment Supplementation Trials (CREST) aim to investigate the potential impact of macular pigment (MP) enrichment, following supplementation with a formulation containing 10 mg lutein (L), 2 mg zeaxanthin (Z) and 10 mg meso-zeaxanthin (MZ), on visual function in normal subjects (Trial 1) and in subjects with early age-related macular degeneration (AMD; Trial 2).
  
  
  METHODS
  CREST is a single center, double-blind, randomized clinical trial. Trial 1 (12-month follow-up) subjects are randomly assigned to a formulation containing 10 mg L, 10 mg MZ and 2 mg Z (n = 60) or placebo (n = 60). Trial 2 (24-month follow-up) subjects are randomly assigned to a formulation containing 10 mg L, 10 mg MZ, 2 mg Z plus 500 mg vitamin C, 400 IU vitamin E, 25 mg zinc and 2 mg copper (Intervention A; n = 75) or 10 mg L and 2 mg Z plus 500 mg vitamin C, 400 IU vitamin E, 25 mg zinc and 2 mg copper (Intervention B; n = 75). Contrast sensitivity (CS) at 6 cycles per degree represents the primary outcome measure in each trial. Secondary outcomes include: CS at other spatial frequencies, MP, best-corrected visual acuity, glare disability, photostress recovery, light scatter, cognitive function, foveal architecture, serum carotenoid concentrations, and subjective visual function. For Trial 2, AMD morphology, reading speed and reading acuity are also being recorded.
  
  
  CONCLUSIONS
  CREST is the first study to investigate the impact of supplementation with all three macular carotenoids in the context of a large, double-blind, randomized clinical trial.
authors.affiliation: Macular Pigment Research Group, Department of Chemical and Life Sciences, Waterford Institute of Technology , Waterford , Ireland and.
authors.forename: Kwadwo Owusu
authors.initials: KO
authors.lastname: Akuffo
authors.forename: Stephen
authors.initials: S
authors.lastname: Beatty
authors.forename: Jim
authors.initials: J
authors.lastname: Stack
authors.forename: Jessica
authors.initials: J
authors.lastname: Dennison
authors.forename: Sarah
authors.initials: S
authors.lastname: O'Regan
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Meagher
authors.forename: Tunde
authors.initials: T
authors.lastname: Peto
authors.forename: John
authors.initials: J
authors.lastname: Nolan
mesh_terms: D000328:Adult; D000368:Aged; D015350:Contrast Sensitivity / Q000187:drug effects*; D019587:Dietary Supplements; D004311:Double-Blind Method; D004338:Drug Combinations; D005260:Female; D005500:Follow-Up Studies; D019466:Glare; D064368:Healthy Volunteers; D006801:Humans; D014975:Lutein / Q000008:administration & dosage*; D008268:Macular Degeneration / Q000517:prevention & control*; D008297:Male; D004364:Pharmaceutical Preparations; D010783:Photometry; D012107:Research Design; D012168:Retinal Pigments; D018434:Sickness Impact Profile; D011795:Surveys and Questionnaires; D041623:Tomography, Optical Coherence; D014792:Visual Acuity / Q000502:physiology; D014815:Vitamins / Q000008:administration & dosage*; D024341:Xanthophylls / Q000008:administration & dosage*; D065146:Zeaxanthins
chemical_list: D004338:Drug Combinations; D004364:Pharmaceutical Preparations; D012168:Retinal Pigments; D014815:Vitamins; D024341:Xanthophylls; D065146:Zeaxanthins; C584722:meso-zeaxanthin; D014975:Lutein