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Kelvin H Wan, Alexander Lam, Christopher Kai-Shun Leung; Impact of Beta-Zone Parapapillary Atrophy (PPA) on Optical Coherence Tomography Angiography (OCT-A) Measurement of Parapapillary Retinal Nerve Fiber Layer Vessel Density (RNFL-VD) for Evaluation of Glaucoma. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4984. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the association between RNFL-VD measurement and PPA area and the impact of PPA on RNFL-VD measurement in glaucoma evaluation.
157 eyes from 50 healthy individuals and 107 primary open angle glaucoma patients had parapapillary RNFL-VD and circumpapillary RNFL thickness (cpRNFLT) measured with a swept-source OCT (Triton OCT, Japan) and visual field measured with standard automated perimetry. Glaucoma was defined as having a narrowed rim/thinned RNFL with corresponding visual field defects. The PPA area was measured from the OCT enface images with reference to the optic disc photographs (Fig.1). Eyes with spherical equivalent of <-6 diopters were excluded. The associations among RNFL-VD, cpRNFLT, visual field and other ocular parameters were analyzed with linear regression modeling. Area under the receiver operating characteristic curves (AUC) of RNFL-VD and cpRNFLT for detection of glaucoma was compared between the groups with and without PPA.
13 (26.0%) normal eyes and 72 (67.3%) glaucomatous eyes had PPA. Visual field MD/VFI did not differ between glaucomatous eyes with and without PPA (p≥0.302). RNFL-VD and cpRNFLT were smaller in glaucoma eyes with and without PPA compared with normal eyes (p≤0.018). RNFL-VD was significantly associated with PPA area after adjusting for cpRNFLT and visual field MD. There was no significant difference in the diagnostic performance for detection of glaucoma between RNFL-VD (AUC=0.78±0.05) and the PPA area (AUC=0.73±0.08) (p=0.510). The AUC of RNFL-VD for detection of glaucoma was significantly reduced when the PPA region was excluded from the analysis (0.78±0.05 vs 0.72±0.06, p=0.005). The AUC of cpRNFLT for detection of glaucoma was similar between the groups with and without PPA (0.98±0.01 vs 0.95±0.03, p=0.337), whereas the AUC of RNFL-VD was greater in eyes with PPA (0.86±0.03) than those without (0.65±0.06) (p=0.005).
RNFL-VD was significantly associated with the area of PPA and they had a similar diagnostic performance for detection of glaucoma. The ability of RNFL-VD to detect glaucoma was dependent on the presence of PPA.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
top panel: glaucoma eye with β-PPA (MD = -1.14dB, RNFL-VD = 58.7%, RNFL = 70µm, PPA Area = 0.89mm2), bottom panel: glaucoma eye without β-PPA (MD = -1.69dB, RNFL-VD = 69.6%, RNFL = 68µm)
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