The effect of human in vivo accommodation on crystalline lens stability
- Ronald A Schachar (ron{at}2ras.com),
- Carlos Davila (cd{at}engr.smu.edu),
- Barbara K Pierscionek (b.pierscionek{at}ulster.ac.uk),
- Wickham Chen (wickham{at}engr.smu.edu),
- Warren W Ward (wward{at}fourward.com)
- University of Texas at Arlington, United States
- Southern Methodist University, United States
- University of Ulster, Northern Ireland
- Southern Methodist University, United States
- Fourward Technnologies, United States
- Published Online First 10 January 2007
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.
