Comparison of Macular Thickness Measurements between Time Domain and Spectral Domain Optical Coherence Tomography

¹ Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, 3/F, Chinese University of Hong Kong Eye Center, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon City, nil, Hong Kong; Ophthalmology, Hamilton Glaucoma Center, 9500 Gilman Drive, La Jolla, California, 92093, United States
² Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Kowloon City, Hong Kong
³ Ophthalmology, UCSD Glaucoma Center, La Jolla, California, United States
⁴ Department of Ophthalmology & Visual Sciences, HongKong, China; Shantou University medical college, The STU/CUHK Joint Shantou International Eye Centre (JSIEC), Shantou University Medical College, P. R. China., Shantou, 515041, China
⁵ Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
⁶ Ophthalmology & Visual Sciences, Chinese University of Hong Kong, Kowloon, Hong Kong

^* To whom correspondence should be addressed. E-mail: cksleung{at}gmail.com.

	Abstract

PURPOSE: To compare macular thickness measurements obtained from time domain optical coherence tomography (OCT) and spectral domain OCT and to evaluate their repeatability and agreement. METHODS: Thirty-five healthy normal subjects were included. In one randomly selected eye in each subject, three serial macular measurements were obtained from time domain OCT (Stratus OCT, Carl Zeiss Meditec, Dublin, CA, USA) and spectral domain OCT (3D OCT, Topcon, Tokyo, Japan) by an experienced technician in a random order. Total and regional macular thicknesses obtained by the 2 OCTs were compared. Their agreement was examined with Bland Altman plots. Repeatability [2.77 x Within subject standard deviation (Sw)], coefficient of variation (CVw) (Sw / overall mean), and intraclass correlation coefficient (ICC) were calculated to evaluate repeatability. RESULTS: Low variability for macular thickness measurements were found in both time domain and spectral domain OCTs. The range of the respective CVw and ICC values were 1.6%-3.2% and 0.85-0.91 for Stratus OCT, and 0.6%-2.4% and 0.92-0.99 for 3D OCT. 3D OCT demonstrated better repeatability for total and regional macular thicknesses (all with p0.014). The foveal and total macular thicknesses measured by 3D OCT were significantly greater than those measured by Stratus OCT (both with p<0.001). The spans of 95% limits of agreement for foveal and total macular thicknesses were 33.9µm and 21.3µm, respectively. CONCLUSIONS: While both time domain and spectral domain OCTs are reliable for macular thickness measurements, spectral domain OCT has better measurement repeatability compared with time domain OCT. Macular measurements obtained from the two OCT systems may not be used interchangeably.

Key Words: optical coherence tomography, image analysis, macular thickness measurement, spectral domain OCT, time domain OCT