Lutein/zeaxanthin intake and visual outcomes in adults with healthy eyes: qualitative gap analysis

<b>Purpose</b>: Scientific evidence suggests a role for lutein and zeaxanthin, in visual function. The purpose of this research was to summarize the data related to lutein/zeaxanthin intake and visual outcomes in adults with healthy eyes using evidence mapping methods and to describe the research to date that would be useful in guiding future research priorities, systematic reviews, and meta-analyses. <b>Design</b>: A search of Medline®, Cochrane Central, and CAB databases was performed for studies of all designs published from 1946 to October 2016. Our search strategy included lutein, zeaxanthin, meso-zeaxanthin, xanthophylls and carotenoids as well as visual outcomes to include macular pigment density (MPD). <b>Results</b>: Forty-seven studies published in English language were identified and mapped. Most research was conducted in controlled parallel trials (77%) using lutein/zeaxanthin supplements. Studies evaluated effects of lutein/zeaxanthin supplementation (66%) or lutein/zeaxanthin in combination with other nutrients (17%); or evaluated foods rich in lutein/zeaxanthin (17%). MPD (89%) was the most common outcome measure studied. Additional outcome measures included in 47 studies were visual acuity (23%), contrast sensitivity (17%), glare sensitivity (13%), and photostress recovery (11%). <b>Conclusions</b>: This study using evidence mapping found that studies evaluating lutein/zeaxanthin supplementation or intake and visual outcomes had MPD as the most common outcome. We conclude that there is sufficient research to warrant a future systematic review/meta-analysis evaluating the role of lutein/zeaxanthin and visual outcomes in participants with healthy eyes. Of interest would be a systematic review of the studies that evaluated both MPD and visual function to determine the strength of the relationship between these two outcomes in healthy adults.

研究目的：科学证据表明，叶黄素（lutein）与玉米黄质（zeaxanthin）在视觉功能中发挥重要作用。本研究旨在通过证据图谱法，汇总健康成人叶黄素/玉米黄质摄入与视觉结局的相关数据，并梳理现有研究进展，为未来研究优先级制定、系统评价与荟萃分析提供参考依据。
研究设计：检索Medline®、Cochrane Central及CAB数据库，纳入1946年至2016年10月发表的所有类型研究文献。本次检索策略涵盖叶黄素、玉米黄质、中玉米黄质（meso-zeaxanthin）、叶黄素类（xanthophylls）及类胡萝卜素（carotenoids），同时纳入视觉结局指标，包括黄斑色素密度（macular pigment density, MPD）。
研究结果：最终筛选并纳入47篇英文发表的研究并进行证据图谱分析。其中绝大多数研究（77%）为采用叶黄素/玉米黄质补充剂的平行对照试验。研究干预类型分为三类：叶黄素/玉米黄质单一补充干预（66%）、叶黄素/玉米黄质与其他营养素联合补充干预（17%），以及富含叶黄素/玉米黄质的食物摄入干预（17%）。本次研究中最常用的结局指标为黄斑色素密度（MPD，89%），其余纳入的结局指标包括视力（23%）、对比敏感度（17%）、眩光敏感度（13%）与光应激恢复率（11%）。
研究结论：本证据图谱研究显示，针对叶黄素/玉米黄质补充或摄入与视觉结局的相关研究中，黄斑色素密度（MPD）是最常用的结局指标。综上，现有研究已足够支撑开展后续系统评价/荟萃分析，以明确叶黄素/玉米黄质在健康眼部人群视觉功能中的作用。值得关注的是，可针对同时评估MPD与视觉功能的研究开展系统评价，以明确健康成人中这两项指标间关联的强度。