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–time difference and amplitudes of Purkinje images I (PI) and IV (P1V) were measured in 37 normal emmetropic subjects (34 women and 3 men; mean age 19.8, range 18–22 years) when they changed focus from 70 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 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 15 cm; however, 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.
- DPI, dual Purkinje image
- PI, Purkinje image I
- PIV, Purkinje image IV
- UBM, ultrasound biomicroscopy
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Published Online First 10 January 2007
Competing interests: RAS has a financial interest in the surgical reversal of presbyopia and WWW has a financial interest in eyetracking.