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Dongwon Lee, Monica Chen, Toco Yuen Ping Chui, Benjamin Epstein, Robert Ritch, Richard B Rosen, Alfredo Dubra, Donald Hood; Adaptive Optics Imaging of Peripapillary Nerve Fiber Bundles: Implications for Glaucomatous Damage Seen on Circumpapillary OCT Scans.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4555.
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© ARVO (1962-2015); The Authors (2016-present)
To better understand glaucomatous damage seen on circumpapillary disc scans obtained with optical coherence tomography (OCT), these scans were compared to images of the peripapillary retinal nerve fiber (RNF) bundles obtained with an adaptive optics/scanning light ophthalmoscope (AO-SLO).
Six eyes of 6 glaucoma patients with arcuate defects within the macular region on 10-2 visual fields were tested using a prototype AO-SLO system and frequency-domain OCT circular (1.7 mm radius) disc scans (3D-OCT2000, Topcon). With OCT, circumpapillary images were obtained and RNF layer (RNFL) thickness compared to machine controls. With the AO-SLO, images of RNF bundles were obtained near the edge of the optic disc. These images were montaged, and co-registered with a fundus photograph. The OCT and AO-SLO images were compared after aligning the images via corresponding blood vessels.
All 6 eyes had an abnormally thin RNFL on OCT scans and abnormal regions of RNF bundles on AO-SLO images in corresponding regions of the disc. However, regions of abnormal, but equal, RNFL thickness on OCT scans varied in appearance on AO-SLO images. These regions could be largely devoid of RNF bundles (5 eyes, Fig. 1A, red arrows), have abnormal appearing bundles of lower contrast (6 eyes, Fig. 1B, orange arrow), or have isolated areas with a few relatively normal appearing bundles (2 eyes, Fig. 1A, yellow arrow). There were local variations in reflectivity, as well as thickness, of the OCT RNFL that corresponded to the variations in RNF bundle appearance.
Relatively similar 10-2 visual field defects with similar OCT RNFL thickness profiles can have very different degrees of RNF bundle damage as seen on AO-SLO. While the results point to limitations of OCT RNFL thickness as typically analyzed, they also illustrate the potential for improving OCT by attending to variations in local intensity. 1. Dubra, Sulai (2011) Biomed Opt Exp.
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