The pilocarpine-induced ciliary body contraction affects the elastic modulus and collagen of cornea and sclera in early development.

The aim of this study was to investigate the effects of pilocarpine-induced ciliary body constant contraction for a long time period on the elastic modulus and collagen in corneal and scleral tissues in the early developmental stage. Twelve one-month-old New Zealand white rabbits were randomly monocularly treated with pilocarpine to cause ciliary body constant contraction. After 1- and 2-months, the sclera tissues and the eyeballs were obtained to assess the cornea and three regions of the sclera-anterior, equatorial and posterior. The corneal tissues and the three regions of the scleral tissues were cut into strips for elastic modulus measurement using an Instron 5544, the size distribution of collagen fibrils was examined using electron microscopy, the samples were homogenized, and the concentration of hydroxyproline was measured to determine the collagen content. For corneal tissues, long-term pilocarpine-induced ciliary body constant contraction did not affect the elastic modulus and collagen. For scleral tissues, long-term pilocarpine-induced ciliary body constant contraction affected the elastic modulus, diameter of collagen fibrils and collagen content in the equatorial and posterior sclera, however, the anterior sclera were unaffected. These results suggested that pilocarpine-induced ciliary body contraction could affect the scleral structure and lead to deformation of the sclera and eyeball, thereby affecting visual functions function in the process of ocular emmetropization.