The anatomy of the ciliary region of the chicken eye.

PURPOSE: To describe the detailed anatomy of the ciliary region of the chicken eye.
METHODS: Fifty-two eyes from White Leghorn chickens were examined in the course of this study. Descriptions are based on specimens examined using microdissection and bright field microscopy of sections embedded in paraffin or epon. Microdissection was assisted through the use of an iodine-based stain.
RESULTS: The ciliary region of the chicken eye is asymmetric through the horizontal plane, with the distance from the limbus to the equator of the eye being greatest temporally. This asymmetry is reflected in the relative development of the ciliary musculature. The nasal ciliary muscle fibers are the shortest of any of the quadrants, and the nasal quadrant lacks a well-developed scleral venous sinus. The ciliary musculature is approximately 2.5 mm in extent (temporally) and is composed of two regional groups (anterior and posterior) within which five distinct arrangements of muscle fibers can be recognized. The majority of fibers insert on fibrous elements associated with the inner or outer walls of the scleral venous sinus, which, in turn, are continuous with the inner stromal elements of the cornea.
CONCLUSIONS: The ciliary musculature of the chicken eye is composed of two major muscle groups within which five arrangements of muscle fibers have been identified. The anatomy of the ciliary muscle is consistent with the recently proposed functions of altering the corneal curvature for corneal accommodation and moving the ciliary body anteriorly as a part of the lenticular accommodative mechanism. The ciliary muscle also may serve in the regulation of aqueous dynamics within the eye.