Changes in astigmatism with accommodation.
An experiment is described in which changes in ocular astigmatism were recorded over an accommodation stimulus range of 0-4 D, in the right eyes of a group of 31 normal subjects aged 17-37 years. The visual axes were horizontal and the observation conditions were monocular. Although subjects had a range of spherical ametropia, all had initial astigmatism of 1.0 DC or less. It was found that, for most subjects in the group, astigmatism changed in the with-the-rule direction, the mean change being -0.036 DC at axis 176 deg for each dioptre of accommodation response. It is speculated that these changes might reflect increases in lens tilt about a horizontal axis, caused by the combined effects of a slacker zonule and gravity.
Radhakrishnan
Hema
H
Faculty of Life Sciences, Moffat Building, University of Manchester, Manchester, UK. hema.radhakrishnan@manchester.ac.uk
Charman
W Neil
WN
D000065:Accommodation, Ocular / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D001251:Astigmatism / Q000503:physiopathology*; D006801:Humans; D007908:Lens, Crystalline / Q000502:physiology*; D008954:Models, Biological; D014787:Vision Tests / Q000379:methods*