Characterization of nonpathological intrascleral cartilage in the domestic sheep (Ovis aries)

Abstract

Birds, cartilaginous and teleost fish, reptiles, and some amphibians have intrascleral cartilage and/or bone; however, these are rarely reported in therian mammals. This study aimed to investigate and characterize a nonpathological formation of cartilage in the posterior sclera of sheep macroscopically, histologically, and by immunohistochemical exam (IHC). Ninety eyes from 45 domestic sheep were collected, underwent gross examination, fixed in formalin, and embedded in paraffin for the microscopical assessment. Sections with histological shreds of cartilage were selected to perform IHC to confirm the presence of cartilage. Intrascleral cartilage was detected in 60 eyeballs (66.66%) from 37 sheep (82.22%). A slight whitish thickening was grossly seen in the posterior sclera. The histologic exam revealed a few scattered, isolated chondrocytes to larger aggregates of cartilaginous islands in the posterior sclera. Eighteen (30%) of 60 eyeballs revealed marked anti-collagen type II immunolabeling. The development of cartilaginous structures in the eyes is considered rare in mammalian animals. The high occurrence of intrascleral cartilage in the examined sheep eyes suggests that this finding corresponds to an anatomical component of sheep sclera, despite the age, breed, or body condition.

A retinoscopic survey of donkeys and goats

“…Affected goats included both sexes and a wide range of breeds and ages. In a recent study by Teodoro et al, intrascleral cartilage was also demonstrated both histopathologically and immunohistochemically in 60 globes (67%) of 37 sheep (82%) 49 . To the best of our knowledge, these two studies are the first to report on intrascleral bone or cartilage in the normal globe of a mammalian species, 48,49 resembling the scleral ossicles of birds 50 .…”

“…In a recent study by Teodoro et al, intrascleral cartilage was also demonstrated both histopathologically and immunohistochemically in 60 globes (67%) of 37 sheep (82%). 49 To the best of our knowledge, these two studies are the first to report on intrascleral bone or cartilage in the normal globe of a mammalian species, 48,49 resembling the scleral ossicles of birds. 50 The presence of bone or cartilage in the sclera may restrict age-related changes in globe dimensions and refractive errors.…”