THE CILIARY GANGLION AND VITREOUS CAVITY SHAPE

Purpose. To learn the influence of the ciliary ganglion on the postnat al growth of eyes with unimpaired visual input and of eyes beneath an image diffusing goggle. Methods. Newborn chicks received unilateral ci liary ganglionectomy or unilateral sham operation and were reared eith er with or without a goggle ipsilateral to the surgical procedure. Ocu lar refractions and ultrasound measurements were made on anesthetized chicks; eyes enucleated postmortem were measured in axial and equatori al dimensions with calipers and studied histologically. Results. Exces sive growth of open eyes in the equatorial dimensions followed ciliary ganglionectomy and became more pronounced as the chicks grew older. T here was only a modest increase in axial growth. Ganglionectomy also i nduced relative hyperopia; lens thinning contributed to this effect an d likely was a direct result of disrupted parasympathetic input to the ciliary muscle. Ganglionectomy also slightly increased the thickness of the choroid in the posterior pole but not in more peripheral locati ons. Conclusion. We conclude that the ciliary ganglion exerts an inhib itory influence on the postnatal growth of open eyes; the main effect is in the equatorial dimension of the vitreous cavity, with a smaller effect on axial length. Ciliary ganglionectomy exerted minimal influen ce on the development of experimental myopia, known to be induced by t he goggle regimen. The amount of equatorial expansion in goggle-induce d myopia was greater than after ganglionectomy alone, indicating that other factors besides the ciliary ganglion can influence the equatoria l dimension of the vitreous cavity.