Peripheral light focusing as a potential mechanism for phakic dysphotopsia and lens phototoxicity

  1. L. Stephen Kwok1,
  2. Damian C. Daszynski2,3,
  3. Valerian A. Kuznetsov1,2,
  4. Therese Pham2,
  5. Arthur Ho2,
  6. Minas T. Coroneo1

Article first published online: 8 MAR 2004

DOI: 10.1111/j.1475-1313.2004.00181.x

Issue

Ophthalmic and Physiological Optics

Ophthalmic and Physiological Optics

Volume 24, Issue 2, pages 119–129, March 2004

Additional Information

How to Cite

Kwok, L. S., Daszynski, D. C., Kuznetsov, V. A., Pham, T., Ho, A. and Coroneo, M. T. (2004), Peripheral light focusing as a potential mechanism for phakic dysphotopsia and lens phototoxicity. Ophthalmic and Physiological Optics, 24: 119–129. doi: 10.1111/j.1475-1313.2004.00181.x

Author Information

  1. 1

    Department of Ophthalmology, Prince of Wales Hospital, The University of New South Wales, Sydney, NSW 2052

  2. 2

    Cooperative Research Centre for Vision, and Cornea and Contact Lens Research Unit, School of Optometry, The University of New South Wales, Sydney, NSW 2052, Australia

  3. 3

    Institut für Augenoptik, Gartenstrasse 133, 73430 Aalen, Germany

*Correspondence and reprint requests to: L. Stephen Kwok. Tel.: +61 2 9382 2480; Fax: +61 2 9382 2488. E-mail address: s.kwok@unsw.edu.au

Publication History

  1. Issue published online: 8 MAR 2004
  2. Article first published online: 8 MAR 2004
  3. Received: 15 October 2003 Revised form: 18 December 2003 Accepted: 12 January 2004

SEARCH

SEARCH BY CITATION

ARTICLE TOOLS

View Full Article (HTML) Get PDF (336K)

Keywords:

  • cataract;
  • contact lens;
  • cornea;
  • eye;
  • lens;
  • peripheral light;
  • ultraviolet

Abstract

Our aim was to examine secondary image formation in the anterior segment caused by peripheral light focusing (PLF) in the human cornea, and in particular the crystalline lens. Non-sequential ray-tracing (OptiCAD) was applied to an anatomically based human eye model, which incorporates a gradient index crystalline lens. For analysis of the limbal effect, we varied the incident angle from 100 to 122°, while for the crystalline lens effect, the incident angle was varied from 60 to 90°. The corneal shapes studied included central radii from 7.4 to 8.2 mm with a range of shape factors. In each case, we computed the peak and average intensities, and the area of exposure at the limbus or lens periphery. The computation was repeated with a previous model eye for comparison. For the limbal effect, a peak intensity gain of ×22.5 was found at an incident angle of 104° which compares well with previous results. The average intensity gain at this angle was ×7.5 over an area of 0.23 mm2. Steeper corneal curvature produced a greater PLF effect. For the crystalline lens effect, maximum UVA (365 nm) intensity gain peaked at ×8.6 at 84° with average intensity gain of ×2.3. The area of UVA exposure peaked at 4.7 mm2 at 70°. A relatively wide range (30°) of incident angles produced peak PLF gains of ×3 or more in the lens. Significant focusing of light is directed to the nasal limbus, and to a lesser extent to the crystalline lens over a broad range of incident angles. PLF in the nasal cornea is reduced by an order of magnitude when a UV-blocking soft contact lens is used. The concentration levels and intraocular sites of PLF action on UV and visible light suggest a new mechanism of phakic dysphotopsia and lens phototoxicity.

View Full Article (HTML) Get PDF (336K)