Refractive changes associated with oblique viewing and reading in myopes and emmetropes.

The effect of brief periods of monocular oblique viewing on axial refractive error in myopes and emmetropes was studied in 20 normal subjects. Refractive error and higher order aberrations were measured either with the subject's head positioned such that the subject looked straight into an aberrometer with the right eye or the subject's head rotated to the right or left by approximately 30 degrees so that the subject had to make an eye rotation of the same angle to see the aberrometer's fixation target. In the first experiment, 10 measurements of wavefront aberration were taken over a period of 3 min at each head position. The refractive changes with oblique viewing showed high levels of intersubject variability. Some subjects showed evidence of systematic change in refraction with oblique viewing. All subjects showed pupil constriction. In the second experiment, after the initial measurement of central and oblique refraction, subjects were made to binocularly read a text placed at 25 cm for 20 min, and the refraction measurements were repeated. No systematic changes in refraction were noted during oblique viewing after 20 min of reading. The data from Experiment 1 give some support for the view that short-term pressures from structures external to the eye may affect its axial refraction. However, the results from Experiment 2 suggest that any such pressures during short-term reading tasks have no significant impact on the axial refraction.