The Naturally Occurring Accommodative Response of the Oscar, Astronotus ocellatus, to Visual Stimuli

Observation of the naturally-occurring accommodative response of a highly visual teleost species provides the opportunity to study its stimulus-response accuracy. A video recording system, linked to a computer digitizing program, was used to measure accommodative changes in lens position in the oscar, Astronotus ocellatus, in response to known food stimuli. The largest lens deviations occurred along an axis c. 22 deg from the pupillary plane. Consistent underaccommodation was reported for the closest of targets, a finding reminiscent of accommodative lag reported in human studies.