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 speci mens examined using microdissection and bright field microscopy of sec tions embedded in paraffin or epon. Microdissection was assisted throu gh the use of an iodine-based stain. Results. The ciliary region of th e chicken eye is asymmetric through the horizontal plane, with the dis tance from the limbus to the equator of the eye being greatest tempora lly. This asymmetry is reflected in the relative development of the ci liary musculature. The nasal ciliary muscle fibers are the shortest of any of the quadrants, and the nasal quadrant lacks a well-developed s cleral venous sinus. The ciliary musculature is approximately 2.5 mm i n extent (temporally) and is composed of two regional groups (anterior and posterior) within which five distinct arrangements of muscle fibe rs can be recognized. The majority of fibers insert on fibrous element s associated with the inner or outer walls of the scleral venous sinus , which, in turn, are continuous with the inner stromal elements of th e cornea. Conclusions. The ciliary musculature of the chicken eye is c omposed of two major muscle groups within which five arrangements of m uscle fibers have been identified. The anatomy of the ciliary muscle i s consistent with the recently proposed functions of altering the corn eal curvature for corneal accommodation and moving the ciliary body an teriorly as a part of the lenticular accommodative mechanism. The cili ary muscle also may serve in the regulation of aqueous dynamics within the eye.