Optic Disc Perfusion in Primary Open Angle and Normal Tension Glaucoma Eyes Using Optical Coherence Tomography-Based Microangiography

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.

Optical Coherence Tomography Angiography in Glaucoma: A Review

“…A significant correlation was found between the OCTA parameters and visual field MD, between OCTA parameters and glaucoma stage, and, as previously described, between the OCTA and OCT parameters in the peripapillary area [6, 17-20, 22-24, 26, 28-30, 33, 35, 36, 38, 39, 41, 45, 48, 50, 71-75], the optic disc [19, 23, 29, 36, 51-53, 57, 58], and the macular area [21, 36, 38, 61, 62, 64, 69, 75, 76]. As mentioned above, the results for the parafoveal area were not significant in some of the studies [38, 70].…”

“…Most studies investigated the OCTA parameters in the superficial layers (above the inner plexiform layer) [3, 16, 18, 20-22, 25-29, 32-38, 41, 45, 47, 48, 50, 61-63, 69-71, 75-77, 85-88] or in the full-thickness scan [6, 17, 19, 21, 23, 30, 36, 39, 46, 51-54, 56-58, 62, 72, 83]. …”

Discriminatory Power of Superficial Vessel Density and Prelaminar Vascular Flow Index in Eyes With Glaucoma and Ocular Hypertension and Normal Eyes

“…Bojikian et al 6 focused on the prelaminar optic disc perfusion. To compensate for reduced tissue volume in glaucomatous eyes, they introduced the theory of ''normalized flux (flux normalized by the vessel area)'' and reported a significant association between the flux and MD and pattern standard deviation of the visual field, global average retinal nerve fiber layer thickness, cup-to-disc ratio, and rim area.…”

“…To compensate for reduced tissue volume in glaucomatous eyes, they introduced the theory of ''normalized flux (flux normalized by the vessel area)'' and reported a significant association between the flux and MD and pattern standard deviation of the visual field, global average retinal nerve fiber layer thickness, cup-to-disc ratio, and rim area. 6 In glaucomatous eyes, the prelaminar tissue becomes atrophic and reduced in volume; thus, the total flow index might not reflect just local ischemia but local ischemia and loss of the neural tissue itself. To understand local ischemia, the flow index/unit volume is important.…”

“…5 Prelaminar blood perfusion also was reduced in glaucomatous eyes. 6 However, the statistical significance of the OCTA parameters has not been compared to structural parameters, such as the ganglion cell complex or circumpapillary retinal nerve fiber layer thickness (cpNFLT). In the current report, we evaluated the discriminatory power of parameters, such as the peripapillary vessel density of the superficial retina (VD), vascular flow index at the prelaminar region (PLFI), signal strength (SS), cpNFLT, and global loss volume (GLV) of the ganglion cell complex in primary open-angle glaucoma (POAG), ocular hypertension (OH), and normal eyes.…”