Comparison of ultrasonic pachymetry and Fourier-domain optical coherence tomography for measurement of corneal thickness in dogs with and without corneal disease

Abstract

Several ultrasonic and Fourier-domain optical coherence tomography (FD-OCT) pachymeters are used to measure corneal thickness in canine patients and research subjects. This study assessed the reliability of and consistency between two ultrasonic pachymetry (USP) devices, Pachette 3 and Accupach VI, as well as automated and manual measurements obtained using FD-OCT in dogs with and without corneal disease. Corneal thickness measurements were compiled from 108 dogs and analyzed using mixed effects linear regression, with Bonferonni adjustments for post-hoc comparisons, to determine the effects of age, weight and disease state. Data are presented as predicted mean ± standard error. Canine corneal disease can result in marked increases in thickness that frequently exceed the upper limits of measurement of some pachymetry devices developed for human use. In this study, the corneas of dogs with endothelial disease or injury frequently exceeded the upper limits of quantitation of 999 and 800 μm for the Accupach VI and automated FD-OCT pachymeters, respectively. Using values <800 μm, the Pachette 3 generated significantly greater values for central corneal thickness (CCT) than the Accupach VI, manual FD-OCT and automated FD-OCT at 625 ± 7.0, 615 ± 7.2, 613 ± 7.2, and 606 ± 7.4 μm respectively (P < 0.001). Of the two devices where measurements >1000 μm were obtained, manual FD-OCT demonstrated less variability than the Pachette 3. Corneal thickness increased linearly with age and weight with an increase of 6.9 ± 1.8 μm/year and 1.6 ± 0.8 μm/kg body weight (P < 0.005 and P = 0.038, respectively).

Change in Central corneal thickness after Phacoemulsification

“…Positive correlation exists between endothelial cell function and Central corneal thickness (CCT) 5 . Central corneal thickness can be measured by ultrasonic pachymeter 6 . Ultrasonic pachymeters allow surgeons to measure the thickness of the cornea in patients suffering from glaucoma, hypertension or those who are considered for refractive surgery without causing damage to this sensitive organ.…”

The feasibility of clinical evaluation for anterior uveitis through spectral‐domain optical coherence tomography in dogs

“…8 The cornea may become thicker in dogs than in humans because of the less intertwined collagen in the corneal stroma and the absent Bowman's layer. 21,35 Additionally, the classification of clinical cell grade used in this study was not detailed, and the lack of direct comparison with cells appearing on OCT and slit-lamp biomicroscopy are also limitations of this study. Aqueous flare and cell grading by two examiners could also be a limitation in this study.…”

“…Second, the eyes with a corneal thickness of less than 800 μm were included for a better scan quality of the anterior chamber. A previous study also suggested that the use of SD‐OCT in dogs was appropriate when the corneal thickness was less than 800 μm 21 …”

“…A previous study also suggested that the use of SD-OCT in dogs was appropriate when the corneal thickness was less than 800 μm. 21 Third, the pachymetry mode images with a scan quality index of >27 were enrolled. The SD-OCT software in this study was designed to score the scan quality of the pachymetry mode images based on the alignment relative to the cornea, blinking, and motion artifacts.…”

“…20 SD-OCT is already used as an adjunctive imaging modality for assessing corneal pathology in veterinary ophthalmology. 9,20,21 However, to the best of our knowledge, this is the first study to evaluate the anterior chamber in dogs with naturally occurring anterior uveitis through SD-OCT.…”