In vivo evaluation of the cornea and conjunctiva of the normal laboratory beagle using time- and Fourier-domain optical coherence tomography and ultrasound pachymetry.

Abstract

To obtain normative data for the canine cornea and conjunctiva using high-resolution time- and Fourier-domain optical coherence tomography (TD-OCT and FD-OCT) and ultrasound pachymetry (USP). One hundred sixty-eight eyes of 133 healthy young intact laboratory beagles. The cornea and conjunctiva of 16 eyes of 8 healthy young intact female beagles were imaged using FD-OCT. Corneal thickness was measured with FD-OCT and USP, while corneal epithelial thickness and conjunctival epithelial thickness were measured with FD-OCT. The central corneal thickness (CCT) was determined in 152 eyes of 125 healthy young adult intact female (35) and male (90) beagles using TD-OCT. Mixed effects linear regression was used for statistical analysis. The CCT was (mean±standard deviation) 497.54±29.76, 555.49±17.19, and 594.81±33.02μm as measured by FD-OCT, USP, and TD-OCT, respectively. The central, superior paraxial, superior perilimbal corneal epithelial thickness and superior bulbar conjunctival epithelial thickness were 52.38±7.27, 56.96±6.47, 69.06±8.84 and 42.98±6.17μm, respectively. When comparing techniques used for measuring CCT (USP vs. FD-OCT and FD-OCT vs. TD-OCT), USP and TD-OCT generated significantly greater values in comparison with FD-OCT (both P<0.001). For all dogs, CCT increased with increasing age and body weight (both P<0.001) and was higher in intact males vs. females using TD-OCT (P=0.034). High-resolution FD-OCT and TD-OCT provide detailed noninvasive evaluation of in vivo canine anterior segment structures. Normative values of the canine cornea and conjunctiva are reported.