Ciliary Body Structure and Function Is Altered in Long–Term Galactose–Fed Dogs

Abstract

Abstract: : Purpose: Long–term galactose feeding has been observed to result in diabetes–like changes of the cornea, retina and lens. Since previous experimental and clinical studies suggest that diabetes can affect the ciliary processes which produce aqueous humor, we have investigated and observed that aqueous flow is also reduced in long–term galactose–fed dogs (Lane et al, Invest. Ophthalmol Vis Sci. 43(4):, 2002). Moreover, because galactose–feeding results in morphological changes in the ciliary epithelium in rats (Ikebe et al, Acta Soc. Ophthalmol. Jpn. 93: 758–62, 1989), the purpose of this study was to 1) investigate whether similar long–term galactose feeding also results in morphological changes of the ciliary body in dogs and 2) whether these changes can be correlated with decreased aqueous flow. Methods: Twelve male beagle dogs initially 9 months of age were divided into three groups. Four dogs received a normal, control diet, four received a diet containing 30% galactose, and four received a 30% galactose diet for the initial 38 months followed by normal, control diet for the duration of the study (58 months). Following completion of the study, the enucleated eyes were fixed in paraformaldehyde, embedded in paraffin, sectioned, and stained with hematoxylin and eosin. Morphometric analyses of the images were conducted using Image Pro Plus software (Silver Spring, MD). Results: Histological studies were limited to the ciliary processes located on the temporal side of the eye. These studies indicated that both the pigmented and nonpigmented epithelial cells within the ciliary processes were altered by long–term galactose feeding. The area of the nonpigmented epithelial cells decreased and noticeable deterioration of the pigmented epithelial cells occurred. These morphological changes appeared to correlate with reduced aqueous flow in these long–term galactose–fed dogs. Both the morphological changes and corresponding reduction in aqueous flow appeared to be irreversible after an initial 38 months of a galactose diet. Conclusions: Since ciliary processes produce aqueous humor, the observed alterations of ciliary epithelial cells may account for the decrease in aqueous flow.

Keywords: ciliary body • aqueous • diabetes