Comparative evaluation of corneal and limbal epithelial thickness in brachycephalic dogs with and without corneal diseases using spectral domain optical coherence tomography

Objective To evaluate alterations in epithelial thickness during corneal degeneration, corneal pigmentation, and additional features observed through spectral-domain optical coherence tomography (SD-OCT) in brachycephalic dogs.Animals and Procedures The study used 55 eyes from 49 brachycephalic dogs that underwent OCT-containing ophthalmic examinations. The examined eyes were classified into corneal degeneration, corneal pigmentation, and normal groups according to corneal lesions. For each eye, corneal epithelial thickness (CET) in the central cornea and maximum limbal epithelial thickness (maxLET) in 4 quadrants of limbus (superior, inferior, nasal, and temporal) were measured from OCT images. Additional abnormal findings on OCT images, including irregular epithelium, subepithelial hyperreflectivity, and conjunctivochalasis, were also recorded.Results The corneal degeneration group had significantly thinner nasal and temporal maxLETs than that of the normal group (p < .001). In the central corneal OCT image of the corneal degeneration group, an irregular epithelium was observed in 70.6% and subepithelial hyperreflectivity in 82.4%, both of which were significantly higher than the normal group (p < .001). In a comparative analysis, the nasal, temporal, and inferior maxLETs were significantly thinner in the corneal pigmentation group than those in the normal group (p < .001, p < .001, and p = .01, respectively).Conclusions Morphological changes in the limbal epithelium were observed in dogs with corneal degeneration and corneal pigmentation. LET reduction could be associated with their pathogenesis and would be valuable as an additional parameter for corneal diseases.