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

OBJECTIVE: 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). ANIMALS: One hundred sixty-eight eyes of 133 healthy young intact laboratory beagles. PROCEDURES: 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. RESULTS: The CCT was (mean&#xa0;&#xb1;&#xa0;standard deviation) 497.54&#xa0;&#xb1;&#xa0;29.76, 555.49&#xa0;&#xb1;&#xa0;17.19, and 594.81&#xa0;&#xb1;&#xa0;33.02&#xa0;&#x3bc;m 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&#xa0;&#xb1;&#xa0;7.27, 56.96&#xa0;&#xb1;&#xa0;6.47, 69.06&#xa0;&#xb1;&#xa0;8.84 and 42.98&#xa0;&#xb1;&#xa0;6.17&#xa0;&#x3bc;m, 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&#xa0;<&#xa0;0.001). For all dogs, CCT increased with increasing age and body weight (both P&#xa0;<&#xa0;0.001) and was higher in intact males vs. females using TD-OCT (P&#xa0;=&#xa0;0.034). CONCLUSION: 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.