Attenuation Outer Retinal Bands on Optical Coherence Tomography Following Macular Edema

Abstract

Purpose: Macular edema is a common retinal disease which may leave important anatomical and functional sequelaes. Directional fundus imaging consists of comparing on- and off-axis images to reveal angle-dependent reflectance properties of fundus structures, which may be related to misaligned photoreceptors. Here, we analyzed directional optical coherence tomography (OCT) and flood-illumination adaptive optics ophthalmoscopy images to detect evidence of misaligned photoreceptors following macular edema. Methods: Transversal, observational study. Nine patients having recovered a normal macular profile after macular edema due to retinal vein occlusion were included. For each patient, a reference OCT scan (i.e., with the incident beam normal to the fovea) was acquired, and off-axis scans were then acquired by laterally shifting the entry pupil. In addition, in four of these eyes, directional adaptive optics ophthalmoscopy documented the directional variations of cone metrics. Results: Included patients comprised two women and seven men (age range, 19–76 years). Reference OCT scans showed patchy attenuation of the cone outer segment tips and to a lesser extent of the inner segment/outer segment lines in all, but two eyes; these. Increased intensity of the cone outer segment tips and inner segment/outer segment lines could be observed on off-axis scans. Accordingly, fusion images showed 66% average reduction of the length of cone outer segment tips attenuation. In two cases, although reference scans showed continuity of outer bands, focal attenuation was evidenced in off-axis images. Directional adaptive optics ophthalmoscopy imaging showed a strong directional variability of cone counts in these areas, ranging from near absence to roughly two-third of reference values. In each case, directional variations of cone counts paralleled those of the reflectance of outer bands. Conclusion: After macular edema, focal attenuations of the inner segment/outer segment and of the cone outer segment tips lines may be present on OCT. These areas may show a strong directional variability by both OCT and adaptive optics ophthalmoscopy, suggesting that misaligned photoreceptor outer segments contribute to such features. The evaluation of outer retinal damage following macular edema should therefore take into account the optical Stiles–Crawford effect to disambiguate missing from misaligned cones.

Patches of Dysflective Cones in Eyes With No Known Disease

“… 53 Some evidence of local cone directionality changes has been reported around drusen 54 and even eye diseases with no obvious topographical changes. 55 However, we feel that abrupt local changes in pointing direction that are large enough to effectively eliminate all reflections for such small patches of close-packed cones in eyes with no known disease are unlikely. Physical factors force cones to line up with their neighbors.…”

Changes in retinal layers after pars plana vitrectomy for rhegmatogenous retinal detachment

“…Another study investigated photoreceptors after RRD using adaptive optics and showed a signi cant decrease in the density of cones from the rst weeks after surgery in both macula-off and macula-on RRD. 20 This early alteration could explain the atrophy of the ONL layer in the immediate postoperative period as well as the alterations of the cone interdigitation zone and the ellipsoid zone. At 1-year post-operative follow-up, authors also detected an increase in cone density, that can explain the increase of CMT.…”

Directional Optical Coherence Tomography Imaging of Macular Pathology

“…8 This technique was initially used in patients without macular pathology to obtain precise independent thickness measurements of the outer nuclear layer (ONL) and HFL. 9 Subsequently, D-OCT has been used in a few conditions to infer pathological alterations in photoreceptor orientation, [10][11][12] volumetric HFL mapping, 13 and NFL variability. 14 In this study, we acquired D-OCT images in patients over a much broader spectrum of retinal pathologies to investigate whether abnormal patterns of directional reflectivity may be observed.…”