Quantitative Thickness Measurement of Retinal Layers Imaged by Optical Coherence Tomography

Abstract

To report an image analysis algorithm that was developed to provide quantitative thickness measurement of retinal layers on optical coherence tomography (OCT) images. Prospective cross-sectional study. Imaging was performed with an OCT3 commercial instrument in 10 visually normal healthy subjects. A dedicated software algorithm was developed to process the raw OCT images and detect the depth location of peaks from intensity profiles. Quantitative thickness measurements of three retinal layers, in addition to total retinal thickness, were derived. Total retinal thickness measurements obtained by the algorithm were compared with measurements provided by the standard OCT3 software. The total retinal thickness profile demonstrated foveal depression, corresponding to normal anatomy, with a thickness range of 160 to 291 microm. Retinal thickness measured by the algorithm and by the standard OCT3 software were highly correlated (R = 0.98). The inner retinal thickness profile predictably demonstrated a minimum thickness at the fovea, ranging between 58 to 217 microm along the 6-mm scan. The outer retinal thickness profile displayed a maximum thickness at the fovea, ranging between 66 to 107 microm along the 6-mm scan. The photoreceptor outer segment thickness profile was relatively constant along the 6-mm scan through the fovea, ranging between 42 to 50 microm. The intrasubject variabilities of the inner retina, outer retina, and photoreceptor outer segment thickness was 14, 10, and 6 microm, respectively. Thickness measurements of retinal layers derived from OCT images have potential value for objectively documenting disease-related retinal thickness abnormalities and monitoring progressive changes over time.