Dynamic changes of configuration and position of human ciliary body during accommodation

Abstract

To study the changes of the configuration and position of ciliary body of normal human eyes in spontaneous far and near accommodations. The configuration and position in ciliary body of 68 normal human eyes were observed real-timely and measured by high frequency transducer of ultrasound biomicroscopy (UBM), when these eyes focused on given far and near optotypes, respectively. All of these parameters between far and near accommodations were compared by One-Way Analysis of Variance (One-Way ANOVA) and Multivariate ANOVA of General Linear Model (MANOVA of GLM), and were correlated with each other respectively (alpha=0.05). (1) In near accommodation, there were statistically significant increase in the thickness of anterior ciliary body, length of ciliary process, whole area of ciliary body and area of circular fibers. There were statistically significant decreases in width of ciliary process, angle of inner apex, distances between ciliary process and trabecula, iris, scleral spur, and angles between ciliary process and iris, ciliary process and sclera; there was also a certain decrease in angle-opening distance 500 microm from the scleral spur. There were no significant changes in the thickness of posterior ciliary body; area of meridional fibers; angle between sclera and iris and angle between trabecula and iris. (2) Parameters of configuration had close correlation with each other, and it was also true in those of position. But, the correlation between the configuration and position was not significant. In the process of near accommodation, ciliary body shifts forwards and inwards, ciliary process becomes tapered because the harmonious contraction of its circular and meridional muscle fibers. This is consistent with the classical relaxation mechanism of accommodation described by Helmholtz. UBM is a new noninvasive method for real-time studying of the ciliary body changes in far-near accommodating human eyes in vivo.