Abstract
The present study was carried out to investigate the morphological and histomorphometrical characters of irides in dogs, camels, buffalos, and donkeys. The findings of the study revealed that, morphologically, the irides were consisted of an anterior border layer, a middle layer of connective tissue stroma and a posterior layer of pigmented epithelium. Interestingly, the anterior borders of all investigated animals were not enveloped by a distinct epithelial or endothelial lining, but on contrary, the posterior border was covered by pigmented epithelium. The constrictor and dilator iridial muscles were well developed in dogs, weakly developed in donkeys, and with an intermediate position in camels and buffalos. Morphometric analysis revealed significant species differences in the mean total thickness of the iris and its different layers. In addition significant differences were also found between the ratio of the means of different layers to the total thickness of the iris at the pupillary, middle and ciliary borders. In conclusion, these variations might be related to the different lifestyles and visual behaviour of the investigated animals. (c) 2008 Elsevier Ltd. All rights reserved.