Evaluation of the Cornea of Dogs With Dry Eye Disease Using Spectral Domain Optical Coherence Tomography

To evaluate the central corneal thickness (CCT) and corneal epithelial thickness (CET) in dogs affected by dry eye disease (DED) using optical coherence tomography (OCT).

Sixty-three canine eyes were allocated into two groups: healthy dogs, without clinical signs of dry eye disease (DED) and Schirmer tear test-1 (STT-1) values ≥ 15 mm/min (n = 29 eyes), and DED-affected dogs, exhibiting clinical signs of DED and STT-1 values < 15 mm/min (n = 34 eyes). The OCT software automatically generated a 17-section corneal pachymetry map within a 6-mm diameter. The thickness of the corneal epithelium was measured manually. Only scans with a quality score of 27 or greater and proven to be free of motion artifacts were accepted for data collection. The Mann-Whitney U test and Spearman's correlation were used to analyze the data.

When comparing the CET of healthy dogs with dogs DED-affected, a median of 73.0 μm (interquartile range [IQR] = 9.0) and 105.0 μm (IQR = 71.0) were obtained, respectively, demonstrating a statistically significant difference (p < 0.0001). A moderate negative correlation was observed between STT-1 and CET (r = -0.581). A moderate-to-strong inverse association was observed between tear film breakup time (TFBUT) and CET (r = -0.66). Dogs with DED exhibited epithelial thickening accompanied by a marked reduction or loss of hyperreflective epithelial interfaces, as well as increased hyperreflectivity within the epithelial layer.

DED-affected dogs exhibited a pronounced increase in CET. Both STT-1 and TFBUT values were directly associated with CET in DED-affected dogs.