Near work induced corneal aberrations in progressing myopia

Abstract

Purpose: To study whether corneal wavefront aberrations significantly differ between progressing myopes and stable emmetropes after reading.

Methods: Twenty young progressing myopic subjects and twenty young emmetropic subjects participated in the experiment. Corneal topography of the left eye was measured with a videokeratoscope prior to reading and then again after 1 hour and 2 hours of reading. The natural position of the eyelids was photographed in primary gaze and during the reading task.

Results: Both emmetropic and myopic groups showed corneal shape and wavefront changes following 1 hour and 2 hours of reading. The major difference between the two groups was the location and magnitude of the corneal aberration changes, which could be attributed to differences in palpebral aperture in the reading gaze position. A significantly smaller palpebral aperture was found for the myopic group in the reading gaze position (emmetropic group = 8.09 mm ±1.56; myopic group = 7.12 mm ±1.00; p = 0.025). Significant changes were found for myopes and emmetropes in trefoil along 30º and vertical coma following reading. A significant shift in direction of against–the rule astigmatism was found for the myopic group (Cyl. –0.14 X 91°, p = 0.01) but not for the emmetropic group (Cyl. –0.04 X 81°, p = 0.09). Corneal higher order wavefront RMS after reading was significantly increased in myopes compared with emmetropes (pre–reading RMS: emmetropes = 0.22 microns, myopes = 0.25 microns, p = 0.23; post–1 hour reading RMS: emmetropes = 0.23 microns, myopes = 0.31 microns, p = 0.02; post–2 hours reading RMS: emmetropes = 0.25 microns, myopes = 0.33 microns, p = 0.06).

Conclusions: Prolonged narrowing of the palpebral aperture during reading may compromise retinal image quality and thereby provide a cue for eye growth. Corneal wavefront changes following reading tended to be larger and occur closer to the central cornea in myopes compared with emmetropes.