AIM: To assess the repeatability of thickness profiles of corneal epithelium produced by aautomatic hierarchic algorithm that was applied to images obtained by a custom-built ultra-high resolution OCT( UHR-OCT)system.

METHODS: Eighteen left eyes of 18 subjects(23.2±0.9)years; mean age±standard deviation)were imaged twice on non-consecutive days by a custom-built ultra-high resolution OCT(UHR-OCT)system. A hierarchic algorithm based on the axial gradient information and a shortest path search was developed to measure the corneal epithelial thickness profiles from the SD-OCT images.

RESULTS: There was good correlation between theautomatic and manual hierarchy positions of the epithelium( p>0.05, paired t-test). The average epithelial thickness of the 6mm central corneal region determined by the automatic hierarchic algorithm was 52.1±2.1μm, ranging from 50.3±1.8μm to 53.2±2.4μm along the horizontal meridian. The epithelial thickness differences between automatic and manual hierarchy by the UHR-OCT systems were 0.4±0.3μm. The intraclass correlation coefficients(ICC)and coefficients of repeatability(CoR)with repeated UHR-OCT measurements for epithelial thickness were 0.90±0.05 and 1.44±0.01μm respectively.

CONCLUSION:Regarding UHR-OCT system, the custom-developed automatic hierarchy has good repeatability and accuracy for measuring the thickness of corneal epithelium.