Comparative morphological analysis of the zonular apparatus in porcine, feline, and canine species

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Source: Frontiers Medicine

Original: https://www.frontiersin.org/articles/10.3389/fmed.2025.1717670...

Published: 2026-01-14T00:00:00Z

The study characterized and compared the morphology of the zonular apparatus in pigs (n=15), cats (n=8) and dogs (n=4) to identify an optimal model for studying zonular pathophysiology during angle closure. Slit-lamp biomicroscopy, photography, histological staining (hematoxylin-eosin, Masson's trichrome), ex vivo ultrasound biomicroscopy (UBM) and scanning electron microscopy (SEM) were used. Significant interspecies differences were observed in the density, orientation, and insertion patterns of zonular fibers. The sagittal width of the posterior vitreous zonule was narrower than in humans (3–4 mm): 0.56 mm in pigs, 0.40 mm in cats, and 0.30 mm in dogs. UBM detected vitreous zonules in pigs and cats, but not in dogs. Dogs and cats had similar zonular apparatus and ciliary body morphology, with a leaf-like shape and looser arrangement compared to the compact configuration of pigs. SEM showed a consistent architecture of the vitreous zonules in all species. The conclusion recommends pigs or cats for accommodation and pathogenesis studies of glaucoma due to the unique origin of zonular fibers and ubiquitous vitreous zonules.