title: Enhancing performance while avoiding damage: a contribution of macular pigment.
abstract: OBJECTIVE
  To compare action spectra for visual discomfort in the fovea and the parafovea and to determine the effect of macular pigment (MP).
  
  
  METHODS
  Visual discomfort thresholds to lights from 440 to 600 nm were obtained for six young (<35 y), visually normal subjects with a wide range of MP densities (0.10-0.71 at 30' eccentricity). Foveal and parafoveal conditions were assessed. Discomfort thresholds were also obtained for xenon-white light (partially absorbed by MP), and a broadband yellow (outside the absorption band of MP). MP was measured psychophysically using heterochromatic flicker photometry (HFP).
  
  
  RESULTS
  For the parafovea, discomfort sensitivity (1/threshold) increased sharply with decreasing wavelength for all subjects. Commensurate with a subject's MP level, MP significantly reduced visual discomfort to short wavelengths (including xenon-white light) for central viewing.
  
  
  CONCLUSIONS
  MP simultaneously reduces visual discomfort and protects from light damage at short wavelengths. As a result, MP increases the range of safe and comfortable light levels. Because higher light levels enable improved visual sensitivity for fine detail, these findings indicate that the spectral absorption properties and spatial distribution of MP combine to protect the retina while enhancing visual performance. The action spectrum for visual discomfort closely matches the risk for acute light damage to the retinal pigment epithelium, and it is consistent with a major influence from the intrinsically photosensitive retinal ganglion cells containing melanopsin. We suggest that MP interacts with nonimage-forming retinal input to achieve the dual outcomes of visual discomfort reduction and protection from light damage.
authors: Vision Science Laboratory, University of Georgia, Athens, Georgia.
authors: James M
authors: JM
authors: Stringham
authors: D Max
authors: DM
authors: Snodderly
mesh_terms: D000221:Adaptation, Ocular; D000328:Adult; D005260:Female; D006801:Humans; D008266:Macula Lutea / Q000502:physiology*; D008297:Male; D010775:Photic Stimulation; D010783:Photometry; D020795:Photophobia / Q000378:metabolism / Q000503:physiopathology; D012016:Reference Values; D012168:Retinal Pigments / Q000502:physiology*; D012684:Sensory Thresholds; D055815:Young Adult
chemical_list: D012168:Retinal Pigments
keywords: carotenoids; light damage; melanopsin; photophobia; visual acuity; visual discomfort; xanthophylls