Effect of Accommodation on Corneal Topography

Abstract

Purpose: To investigate the effect of accommodation on corneal topography in healthy subjects.Methods: Using a Nidek OPD-Scan ARK-10000, corneal topographic images, images of the iris, and the refraction of 18 eyes of 10 normal subjects with a mean age of 26.3 +/- 7.1 years (median, 24 years; range, 19-41 years) were simultaneously obtained before and during fixation of a near target in the Department of Ophthalmology, Istanbul Medeniyet University Medical Faculty, Istanbul, Turkey. At baseline, iris landmarks, such as nevi and crypts, were identified on each iris image that were on opposite sides of the pupil and 180 degrees apart. A line was drawn on the iris images between these 2 landmarks. The same landmarks were identified on the iris images obtained when the eye was fixating at the near target. A line was drawn between the landmarks. The angular rotation of the lines relative to the vertical meridian was measured to assess cyclotorsion of the eyes during accommodation.Results: At baseline, the mean spherical equivalent refraction of the eyes was -0.78 +/- 0.38 diopters (D) (range, -0.25 to -1.67 D) with <0.5 D of astigmatism. During a mean accommodative amplitude of -4.55 +/- 2.04 (median, -4.25 D; range, -1.75 D to -8.12 D), there was no apparent difference in corneal topography and no statistical difference in mean keratometry (P = 0.26) or cyclotorsion (P = 0.74).Conclusions: During accommodation, the cornea does not change curvature and the eye does not appear to significantly cyclotort.