title: Action spectrum for photobleaching of human lenses by short wavelength visible irradiation.
abstract: OBJECTIVE
  Cataract is the world-leading cause of blindness. In search for a new treatment of cataract we have found that the yellow discolouration of aged human lenses can be photobleached using a non-invasive, infra-red, femtosecond laser treatment. These results were presented in an earlier PlosOne publication. The objective of the study was to characterize the single-photon photobleaching action spectrum of the aged human lens in vitro.
  
  
  METHODS
  Ninety-one human donor lenses were irradiated with continuous wave laser light at 375, 405, 420, 445, 457 or 473 nm. Photobleaching was monitored by photography and transmission measurements.
  
  
  RESULTS
  The action spectrum peaked at 420 nm followed by, in order of decreasing effect, 445, 457, 473, 405 and 375 nm. Younger and less absorbent lenses showed smaller changes than older and more absorbent lenses. There was a dose-dependent increase in lens transmission with increasing laser irradiation.
  
  
  CONCLUSIONS
  For a 75 year old lens an effect corresponding to elimination of 15 years or more of optical ageing was obtained. This study of the spectral characteristics and intensity needed to bleach the human lens with single-photon laser effects found an action-spectrum peak at 420 nm tailing gradually off toward longer wavelengths and more steeply toward shorter wavelengths. The results may be used to guide experiments with two-photon bleaching.
authors.affiliation: Department of Ophthalmology, Glostrup Hospital, Glostrup, Denmark.
authors.forename: Line
authors.initials: L
authors.lastname: Kessel
authors.affiliation: Department of Ophthalmology, Glostrup Hospital, Glostrup, Denmark; Department of Clinical Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Larsen
mesh_terms: D000067549:Action Spectrum; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D002386:Cataract / Q000628:therapy; D006801:Humans; D007834:Lasers; D007908:Lens, Crystalline / Q000528:radiation effects*; D008027:Light; D008875:Middle Aged; D038761:Photobleaching; D010789:Phototherapy