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The effect of human in vivo accommodation on crystalline lens stability
  1. Ronald A Schachar (ron{at}2ras.com),
  2. Carlos Davila (cd{at}engr.smu.edu),
  3. Barbara K Pierscionek (b.pierscionek{at}ulster.ac.uk),
  4. Wickham Chen (wickham{at}engr.smu.edu),
  5. Warren W Ward (wward{at}fourward.com)
  1. University of Texas at Arlington, United States
  2. Southern Methodist University, United States
  3. University of Ulster, Northern Ireland
  4. Southern Methodist University, United States
  5. Fourward Technnologies, United States

    Abstract

    Aim: To determine the effect of human in vivo accommodation on the stability of the crystalline lens.

    Methods: Using a dual-Purkinje image (DPI) eyetracker, the phase difference and amplitudes of Purkinje images I (PI) and IV (P1V) were measured in 37 normal emmetropic subjects (34 females, 3 males; mean age 19.8, range 18-22 years) when they changed focus from 70 cm to 15 cm and simultaneously rotated their heads horizontally from side to side or made horizontal saccades between two targets 6.8° apart.

    Results: When the subjects changed focus from 70 cm to 15 cm and rotated their heads or made eye saccades the phase-time difference between PI and PIV decreased. During saccades, the amplitude of both PI and PIV overshoots significantly increased with focus at 15cm and their ratio (PIV overshoot amplitude/PI overshoot amplitude) significantly declined.

    Conclusions: The lens is stable during accommodation. The implications of these findings on the mechanism of accommodation are discussed.

    • Purkinje images
    • accommodation
    • eyetracker
    • human crystalline lens
    • stability

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