Since the mid 1960's phototropic spectacles and sunglasses have been widely sold. These contain highly active and photo reactive silver halides. In addition to silver chloride, fluoride and bromide, some of these lenses contain small percentages of copper and cobalt. These active and toxic elements significantly increase the X-ray density of such lenses or their fragments and slightly increase the specific gravity of the glass. Inherently slow clearing, compounded by the further delaying effect of high ambient temperature makes these lenses an impediment to twilight and night driving. Maximum clearing requires shielding from all light for many hours. Filters such as these worn under mesopic conditions as in night driving reduce needed incident light on the retina and are progressively more severe impediments with advancing age of the wearer. MacFarland has demonstrated a need for essentially doubled ambient light every thirteen years of adult lift to maintain recognition capabilities under mesopic illumination. Drivers with tinted windshields face compounded reduction of necessary liminous cues when wearing such lenses for mesopic driving tasks. When fragmented, these lenses, like lead glass, are easier to identify by X-ray even when less than 2 mm in size. Conventional crown glass fragments must be larger than 2 mm in size for usual X-ray identification. Active silver and cobalt ions are leached from this glass. Chronic experiment with glass fragments implanted into the vitreous of albino rabbits over 6-8 months shows a tri-phasic reaction consisting of a few days of post insertional inflammation followed by 7-14 days of relative inflammatory quietude and then progressive low grade inflammation over months. This is complicated by vitreous strands and localized hemorrhage about the fragments particularly when they are in contact with the retina. Fragments suspended in mid vitreous evoke lesser localized reaction. Established concepts of minimal extraction efforts for glass fragments may now need to be revised toward more prompt or heroic efforts to remove phototropic elements.

  • Supplemental Notes:
    • Proceedings of the 19th Conference of the American Association for Automotive Medicine.
  • Corporate Authors:

    American Association for Automotive Medicine

    801 Green Bay Road
    Lake Bluff, IL  United States  60044
  • Authors:
    • Kenney, A H
    • Moore, W E
  • Conference:
  • Publication Date: 1975

Media Info

  • Features: Photos;
  • Pagination: 8 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00132035
  • Record Type: Publication
  • Source Agency: Highway Safety Research Institute
  • Files: TRIS
  • Created Date: Jun 5 1976 12:00AM