Comparison of time domain Stratus OCT and spectral domain SLO/OCT for assessment of macular thickness and volume

Abstract

To compare retinal thickness and volume measurements obtained with Stratus time domain optical coherence tomography (OCT) and spectral domain scanning laser ophthalmoscope OCT (SD-SLO/OCT). In a cross-sectional study, 52 eyes with a normal macula, 30 eyes with retinal oedema, and 10 eyes with a myopia higher than 6 D have been evaluated with both time domain OCT (TD-OCT, Stratus OCT, Carl Zeiss Meditec, USA) and SD-SLO/OCT (OTI, Toronto, Canada). Retinal thickness and volume measurements in the nine areas of the 6-mm ETDRS ring were compared. Artefacts were defined as the discordance between the automatically detected anterior and posterior retinal boundaries and the boundaries detected by the examiner. Artefacts were more frequent with TD-OCT (35 vs26%). Mean retinal thickness was significantly higher with SD-SLO/OCT by 30.1 microm (+/-25.8) (P=0.003) in presence of the artefacts and by 39.2 microm (+/-25.8) (P=0.003) after their exclusion. The correlation between the two retinal thickness data sets before exclusion of the artefacts (r=0.59, P<0.001) increased after their removal (r=0.84, P<0.001). A strong correlation was present between the two retinal volume data sets before (r=0.94, P<0.001) and after exclusion of the artefacts (r=0.96, P<0.001). SD-SLO/OCT produced fewer artefacts than Stratus TD-OCT. This could be attributed to the greater resolution and acquisition speed of SD-SLO/OCT. The macular retinal thickness values measured with SD-SLO/OCT were significantly higher than those measured with Stratus TD-OCT. Retinal volumes measured with Stratus TD-OCT and SD-SLO/OCT were strongly correlated.