Interchangeability of macular thickness measurements between different volumetric protocols of Spectralis optical coherence tomography in normal eyes

To evaluate in healthy eyes the interchangeability of retinal thickness measurements resulting from different protocols of Spectralis optical coherence tomography (OCT, Heidelberg Engineering, Germany). Three different central volumetric protocols were performed in one session by one single operator in a randomly selected eye of 31 healthy adults (range, 19-30 years): (1) area 6 x 6 mm, 25 scan pattern (SP), (2) area 6 x 6 mm, 49 SP, (3) area 6 x 3 mm, 97 SP. Nine ETDRS areas were analyzed, except outer areas for 97 SP. Interclass correlation coefficients (ICC) and limits of agreement (Bland-Altman) were calculated. Mean minimal foveal thickness was 224.0 +/- 15.8 mu m and central retinal thickness 280.8 +/- 16.5 mu m. ICC ranged from 0.973 to 0.993. Ninety-five percent limits of agreement between the protocols were < 7 mu m in all ETDRS areas. The difference between two measurements never exceeded 9 mu m. Spectralis OCT retinal thickness measurements in healthy subjects showed good protocol interchangeability for all tested protocols. Larger differences are to be expected in eyes with macular pathology.