Longitudinal imaging of microscopic scattering features in the foveal avascular zone of multiple sclerosis using adaptive optics ophthalmoscopy

Abstract

Purpose : Microscopic structures in the inner retina of the foveal avascular zone (FAZ) that may contribute to visual dysfunction in multiple sclerosis (MS) visible using adaptive optics scanning laser ophthalmoscopy (AOSLO) were recently reported (PMCID: PMC8479576). Here we characterize changes in number, structure and morphology of these light-scattering features over time in order to better understand their nature.

Methods : One eye without history of optic neuritis in two female subjects with stable relapsing-remitting multiple sclerosis (46-65y) underwent standard clinical examination, followed by AOSLO during two visits. Simultaneous reflectance AOSLO confocal and non-confocal split-detection image sequences of the fovea were acquired using 790 nm light. Registered images were averaged and aligned to cover the FAZ. The number, Feret’s diameter, and area of manually segmented structures were measured. A paired t-test was used to compare diameter and area between visits within each subject.

Results : The subjects’ visual acuity was consistent between visits. After a 3 month follow up visit, subject 1 had no new features (18 total); after 11 months, there were two new small features detected in subject 2 (12 total). The diameter of features ranged from 10-95 µm. There was no significant difference in feature diameter between visits for subjects 1 and 2 (p=0.11; p=0.38, respectively). The area of features ranged from 69-3329 µm². Subject 1’s features had a decrease in area between visits (p=0.01), with an average decrease in area of 45 ± 65 µm². Subject 2’s features had an increase in area of 12 ± 84 µm² (p=0.65). The total area of the FAZ covered by features decreased by 7% in subject 1 and 6% in subject 2 between visits. For both subjects, the qualitative appearance of features between visits, as well as the dark shadows on the corresponding photoreceptor mosaic, did not change.

Conclusions : The presence and appearance of microscopic scattering features located in the foveal pit appeared qualitatively similar over a period of 3-11 months in MS subjects who had stable visual acuity, suggesting these could be inanimate structures. However, some small quantitative changes in feature number and size over time were detected; further analysis is needed to determine the biological significance of these changes.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.