Abstract
PurposeTo investigate optic disc perfusion differences in normal, primary open-angle glaucoma (POAG), and normal tension glaucoma (NTG) eyes using optical microangiography (OMAG) based optical coherence tomography (OCT) angiography technique.DesignCross-sectional, observational study.SubjectsTwenty-eight normal, 30 POAG, and 31 NTG subjects.MethodsOne eye from each subject was scanned with a 68 kHz Cirrus HD-OCT 5,000-based OMAG prototype system centered at the optic nerve head (ONH) (Carl Zeiss Meditec Inc, Dublin, CA). Microvascular images were generated from the OMAG dataset by detecting the differences in OCT signal between consecutive B-scans. The pre-laminar layer (preLC) was isolated by a semi-automatic segmentation program.Main Outcome MeasuresOptic disc perfusion, quantified as flux, vessel area density, and normalized flux (flux normalized by the vessel area) within the ONH.ResultsGlaucomatous eyes had significantly lower optic disc perfusion in preLC in all three perfusion metrics (p<0.0001) compared to normal eyes. The visual field (VF) mean deviation (MD) and pattern standard deviation (PSD) were similar between the POAG and NTG groups, and no differences in optic disc perfusion were observed between POAG and NTG. Univariate analysis revealed significant correlation between optic disc perfusion and VF MD, VF PSD, and rim area in both POAG and NTG groups (p≤0.0288). However, normalized optic disc perfusion was correlated with some structural measures (retinal nerve fiber layer thickness and ONH cup/disc ratio) only in POAG eyes.ConclusionsOptic disc perfusion detected with OMAG was significantly reduced in POAG and NTG groups compared to normal controls, but no difference was seen between POAG and NTG groups with similar levels of VF damage. Disc perfusion was significantly correlated with VF MD, VF PSD, and rim area in glaucomatous eyes. Vascular changes at the optic disc as measured using OMAG may provide useful information for diagnosis and monitoring of glaucoma.
Highlights
Glaucoma is the leading cause of irreversible blindness worldwide [1], and elevated intraocular pressure (IOP) remains a major risk factor for its development and progression [2,3]
The visual field (VF) mean deviation (MD) and pattern standard deviation (PSD) were similar between the Primary open-angle glaucoma (POAG) and normal tension glaucoma (NTG) groups, and no differences in optic disc perfusion were observed between POAG and NTG
Optic disc perfusion detected with optical microangiography (OMAG) was significantly reduced in POAG and NTG groups compared to normal controls, but no difference was seen between POAG and NTG groups with similar levels of VF damage
Summary
Glaucoma is the leading cause of irreversible blindness worldwide [1], and elevated intraocular pressure (IOP) remains a major risk factor for its development and progression [2,3]. Recent studies have proposed that POAG and NTG may represent a continuum of open-angle glaucoma that differ primarily in predominant causative risk factors, with higher IOP being important in POAG, while additional IOP-independent factors may be important in NTG [6,7,8]. Vascular dysfunction in the optic nerve head (ONH) has been proposed as a contributing factor in the development and progression of glaucoma, especially in NTG patients [9] This is supported by the increased frequency of optic disc hemorrhage, migraine headaches, Raynaud’s phenomenon, and primary vascular dysregulation syndrome (Flammer syndrome) in NTG patients compared to POAG patients [7, 10,11,12,13]. Several reports have measured directly or have calculated indirectly the ONH blood flow in vivo, using techniques such as intravenous fluorescein angiography (FA), mean ocular perfusion pressure (MOPP), nocturnal hypotension, and C-reactive protein levels, but the results so far are inconsistent [7,14,15,16,17,18,19]
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