The mechanism of accommodation in pigeons.

Abstract

By means of an adapted ophthalmometer it was found possible to measure corneal changes in the pigeon eye. The normal cornea had the curvature of a sphere of 7.75 to 8.00 mm. diam. No effects upon corneal curvature were observed upon dosage with adrenalin, atrophin, or ether. There is some evidence of loss of curvature upon treatment with cocain or curare. Strong nicotine dosage results in considerable corneal flattening. Following death the curvature of the normal cornea increases somewhat. The lens substance was very soft and not apparently laminated nor fibrous. Indices of refraction were: for aqueous humor, 1,3435 for one bird (younger) and 1,341 for the other; for vitreous humor, 1.335 for both birds; and for the lens substance, "somewhere between 1.402 and 1.405." It is suggested that the lens operates in accommodation only by virtue of its position which subjects it to the influence of intra-ocular pressures which are modified by the ciliary muscles.