The effect of accommodation on retinal image size.
The apparent size of an object is diminished when accommodation of the eye moves inward to a position closer to the observer than to a viewed object. This phenomenon is called accommodation micropsia. Using schematic eyes, we investigated change in retinal image size caused by a change in accommodation. The use of schematic eyes is also discussed and is justified. The calculated magnitude of this diminution for four schematic eyes ranged from unity at infinity to a maximum of 0.98 (-2%) at about 12.0 diopters (D). For distances at which accommodation micropsia is typically observed (about 2.0 D), retinal minification is less than 0.997 (-0.3%). Thus changes in the size of the retinal image attributable to accommodation are virtually negligible when compared with the observed reduction of 3% to 33%. This suggests that accommodation micropsia is mediated almost entirely by processes other than those involving the optics of the eye.
Smith
G
G
Department of Optometry, University of Melbourne, Parkville, Victoria, Australia.
Meehan
J W
JW
Day
R H
RH
D000065:Accommodation, Ocular / Q000502:physiology*; D003290:Convergence, Ocular / Q000502:physiology; D006801:Humans; D009903:Optical Illusions / Q000502:physiology*; D055095:Optics and Photonics; D011601:Psychophysics; D012160:Retina / Q000502:physiology*; D012858:Size Perception / Q000502:physiology*