Retinal thickness analysis with time and spectral-domain optical coherence tomography. Cross-platform interchangeability of manual measurements.
OBJECTIVE
retinal thickness values obtained by automated analysis with new spectral-domain optical coherence tomography (OCT) devices exceed those measured by old time-domain OCTs. Aim of the present work is to assess reproducibility and comparability of manual measurements performed on both time-domain and spectral-domain OCT scans.


METHODS
6 eyes were scanned using Stratus OCT3 and Cirrus hd-OCT. Raw exported images were analyzed by ordinary computer software; multiple manual measurements of retinal thickness were taken at different eccentricities. Stratus Retinal Thickness (SRT) was measured from Internal Limiting Membrane (ILM) to the photoreceptors Internal-Outer Segment interface (IS/OS), while two series of measurements were performed in Cirrus images: CRT = Cirrus-RT (from ILM to the Retinal Pigment Epitelium, RPE) and cCRT = corrected-CRT (from ILM to IS/OS). Measurements were repeated twice in two eyes and reproducibility was assessed by Intra-Class correlation (ICC) and Coefficient of Variation (CV). Bland-Altman plots, paired t-test and ICC were used for comparative analysis between Stratus and Cirrus measurements.


RESULTS
Mean SRT, CRT and cCRT values +/- SD were respectively 244.75 +/- 34.78 microm, 275.78 +/- 34.36 microm and 244.95 +/- 33.78 microm. Paired t-test resulted in p<0.0001 comparing SRT and CRT series, versus p=0.6544 between SRT and cCRT series. ICC was 0.65 between SRT and CRT and 0,94 between SRT-cCRT. Reproducibility of the measurements was excellent (CV=2,13% for Stratus and 1,62% for Cirrus; ICC=0,994 for both devices).


CONCLUSIONS
while a systematic error affects comparison of Stratus and Cirrus macular thickness maps, manual linear measurements result interchangeable, hence allowing comparison of images acquired with either OCT systems. (www.actabiomedica.it).
Ophthalmology, University of Parma, Parma, Italy. neri.mail2@gmail.com
Alberto
A
Neri
Elisabetta
E
Delfini
Cristina
C
Casubolo
Claudio
C
Macaluso
D006801:Humans; D007091:Image Processing, Computer-Assisted; D015203:Reproducibility of Results; D012160:Retina / Q000033:anatomy & histology*; D041623:Tomography, Optical Coherence / Q000379:methods*