Improved analysis of the outer foveal microstructure ‐ OCT imaging of healthy and abnormal retina

Abstract

AbstractPurpose To improve visualization and segmentation of the foveal photoreceptors from the level of outer segments to the synapse layer in the inner portion of the outer plexiform layer. Furthermore, to create a normative model of the topography of the outer nuclear layer (ONL) with cone and rod cell bodies and the Henle fiber layer (HFL) with the axons radiating out from the foveal center (FC). An improved separation of ONL and HFL is clinically relevant for the understanding of microstructural changes in abnormal retina.Methods Selected eyes from 14 normals and 5 young adults with a history of prematurity were imaged using a commercial spectral domain optical coherence tomography (SD‐OCT) system. Centered and displaced SD‐OCT entrance beam positions were used to obtain straight and tilted scans, respectively. Horizontal scans through FC with a distinct light reflex were selected for analysis. Straight and tilted SD‐OCT images were flattened to the RPE layer prior to registration and averaging. Retinal layer thickness was measured manually at FC and three lateral positions along the temporal and nasal hemi‐meridians.Results We found a close correspondence between layer thickness measurements at the same lateral positions for both straight and tilted scans. However, a discrepancy was found for the tilt‐up paracentral position for tilted scans, where the foveal slope appeared flatter and the thickness of inner retinal layers was lower than in the straight and tilt‐down positions.Conclusion Improved visualization of HFL/ONL was confirmed in tilted images. Image flattening and registration simplifies measurement of outer foveal layers in normal and abnormal retina.