Corneal shape change during accommodation

Purpose To investigate whether accommodation induces any changes in central corneal curvature. Methods Shape changes were measured on 14 subjects using a keratometer modified to enable a change in focus to occur without a change in vergence. All subjects were emmetropic and their ages ranged from approximately 20 to 28 years. Results In 11 of the 14 subjects a difference in central corneal curvature, of around 0.4 D in at least one principal meridian, was found when focus was changed between distant and near targets. In 9 subjects the curvature was greater for near focus in at least one meridian. In 5 subjects the change in one meridian was opposite in effect to what would be expected, i.e. the curvature was greater at distance than at near. Conclusion The study suggests that accommodation may have some effect on corneal shape.