title: The effects of protective eyewear on glare and crystalline lens transparency.
abstract: OBJECTIVE
  Sunglasses have generally been used to protect against glare. Various kinds of sunglasses which correspond to the visual environment are on the market (e.g. for driving, fishing, skiing, etc.). As for the spectral transmission factor of sunglasses, the differences that occur in user's eyes with aging have not been fully considered. We investigated the relationship between different levels of crystalline lens transparence and the effects of glare protection using two kinds of filters.
  
  
  METHODS
  A Tri-Blocker filter (TB) and general driving filter (ActiveDrive, ADR) were used. The TB absorbs three spectral wavelengths (below 400 nm, blue light, 575 nm) and can be transparent for other visible light. The ADR reduces the light below 650 nm. TB and ADR transmit 52.5 and 29.0% of the visible light, respectively. Twenty-five normal volunteers with transparent lenses (n = 48 eyes, aged from 22 to 68 years) and 10 cortical cataract patients (n = 18 eyes, aged from 48 to 71 years) were selected. The visual acuity of all subjects was 1.0 or better with the best correction. Contrast sensitivity function (CSF) was measured in four simulated light conditions (daylight, daylight with peripheral glare, twilight, twilight with central glare) by MCT8000 (Vistech). The light scattering intensity of the crystalline lens was measured by EAS-1000 (Nidek).
  
  
  RESULTS
  The TB improved the CSF of the elderly volunteers under daylight conditions and of 1 of the cataract patients under all conditions. In the younger group, the CSF did not change under daylight conditions and deteriorated under twilight conditions. Although the ADR was effective for glare protection in the young volunteers, the protective effects of the TB were better than those of ADR for the middle-aged group.
  
  
  CONCLUSIONS
  Sunglasses not only protect against glare but also stabilize visual quality under various light conditions (e.g. passing through a tunnel while driving). Aging changes in lens transparency should be specially considered when developing protective eyewear.
authors.affiliation: Department of Ophthalmology, Kanazawa Medical University, Kahoku-gun, Ishikawa-ken, Japan. yassan-s@kanazawa-med.ac.jp
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Sakamoto
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Sasaki
authors.forename: Masami
authors.initials: M
authors.lastname: Kojima
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sasaki
authors.forename: Akiko
authors.initials: A
authors.lastname: Sakamoto
authors.forename: Masumi
authors.initials: M
authors.lastname: Sakai
authors.forename: Akiyo
authors.initials: A
authors.lastname: Tatami
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D002386:Cataract / Q000503:physiopathology; D015350:Contrast Sensitivity / Q000502:physiology*; D005135:Eye Protective Devices / Q000592:standards*; D019466:Glare; D006801:Humans; D007908:Lens, Crystalline / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D008875:Middle Aged; D012542:Scattering, Radiation