Intra and inter-user reliability of central corneal thickness measurements obtained in healthy feline eyes using a portable spectral-domain optical coherence tomography device

Abstract

Objective: To determine the intra and inter-user reliability of central corneal thickness (CCT) measurements obtained using a portable spectral-domain optical coherence tomography (SD-OCT) device in healthy feline eyes.

Animals: Twenty clinically normal cats.

Procedures: Gentle manual restraint was utilized for proper animal positioning. Central corneal thickness measurements were obtained from both eyes of each animal three times by two operators in succession. A 6 mm, corneal pachymetry protocol was performed using the Optovue® iVue SD-OCT system. The CCT was automatically calculated using the pachymetry software generated from eight radial scans, 6 mm in length. The CCT was recorded for each operator and compared statistically for both intra and inter-user reliability.

Results: Twenty cats (11 CM, 9 SF) with a mean age of 4.7 years were examined. The mean CCT for all eyes examined was 629.08 ± 47.05 μm. No significant difference in CCT was found based on the eye examined (OD vs. OS) or age of the animal. However, the CCT of spayed females was significantly higher (42.64 ± 18.0 μm) as compared to castrated males (P = 0.03). There was no significant difference in CCT measurements between replicates performed by the same operator or between operators. The mean difference in CCT between operators was 0.38 μm. The coefficient of variation for each user and between users was very low (range 0.68-1.5%). The intra-class correlation coefficient comparing operators was 0.975.

Conclusions: The Optovue® iVue SD-OCT device is capable of obtaining CCT measurements with excellent intra and interoperator reliability in healthy feline eyes.

Keywords: central corneal thickness; feline; optical coherence tomography; pachymetry.