Deep Retinal Layer Microvasculature Dropout Detected by the Optical Coherence Tomography Angiography in Glaucoma

Abstract

Purpose To investigate factors associated with dropout of the deep retinal layer microvasculature within the β-zone parapapillary atrophy (βPPA) assessed by optical coherence tomography angiography (OCT-A) in glaucomatous eyes. Design Cross-sectional study. Participants Seventy-one eyes from 71 primary open angle glaucoma (POAG) patients with βPPA enrolled in the Diagnostic Innovations in Glaucoma Study. Methods βPPA deep layer microvasculature dropout was defined as a complete loss of the microvasculature located within deep retinal layer of the βPPA from OCT-A-derived optic nerve head vessel density maps by standardized qualitative assessment. Circumpapillary vessel density (cpVD) within the retinal nerve fiber layer (RNFL) was also calculated using OCT-A. Choroidal thickness and presence of the focal lamina cribrosa (LC) defect were determined using swept-source OCT. Main Outcome Measures Presence of the βPPA deep layer microvasculature dropout. Parameters including age, systolic and diastolic blood pressure, axial length, intraocular pressure, disc hemorrhage, cpVD, visual field (VF) mean deviation (MD), focal LC defect, βPPA area, and choroidal thickness were analyzed. Results βPPA deep layer microvasculature dropout was detected in 37 eyes (52.1%) of eyes with POAG. Eyes with dropouts had a higher prevalence of LC defect (70.3 vs. 32.4%), lower cpVD (52.7 vs. 58.8%), worse VF MD (-9.06 vs. -3.83dB), thinner total choroidal thickness (126.5 vs. 169.1/μm), longer axial length (24.7 vs. 24.0mm), larger βPPA (1.2 vs. 0.76mm2) and lower diastolic blood pressure (74.7 vs. 81.7mmHg) than those without dropouts (P< 0.05, respectively). In the multivariate logistic regression, higher prevalence of focal LC defect (odds ratio [OR], 6.27; P = 0.012), reduced cpVD (OR, 1.27; P = 0.002), worse VF MD (OR, 1.27; P = 0.001), thinner choroidal thickness (OR, 1.02; P = 0.014), and lower diastolic blood pressure (OR, 1.16; P = 0.003) were significantly associated with the dropout. Conclusions Certain systemic and ocular factors such as focal LC defect, more advanced disease status, reduced RNFL vessel density, thinner choroidal thickness, and lower diastolic blood pressure were factors associated with the βPPA deep layer microvasculature dropout in glaucomatous eyes. Longitudinal studies are required to elucidate the temporal relationship between βPPA deep layer dropout and these factors.

Optical Coherence Tomography Angiography in Glaucoma: A Review

“…Parapapillary deep-layer MvD was detected in ± 50% of POAG eyes [90, 91] but not in control eyes [91, 92]. The fact that it corresponded to the perfusion defect shown by indocyanine green angiography indicated that the MvD shown in OCTA represented a true perfusion defect in the choroid or inner sclera [92].…”

“…The fact that it corresponded to the perfusion defect shown by indocyanine green angiography indicated that the MvD shown in OCTA represented a true perfusion defect in the choroid or inner sclera [92]. Eyes with an MvD were found to have a higher prevalence of lamina cribrosa defects, a lower vessel density, a lower visual field MD, and lower RNFL and choroidal thicknesses [90, 91]. The MvD were spatially associated with lamina cribrosa defects [90], RNFL defects [91], and visual field defects [30, 92].…”

An Optical Coherence Tomography Angiography Study of the Relationship Between Foveal Avascular Zone Size and Retinal Vessel Density

“…In this study, we set the cutoff value of OCTA image quality at SSI >48, as used in many previous studies. 23,25,26,36,[39][40][41][42] Venugopal et al recently reported that SSI value had a significant effect on the repeatability of VD measurement by OCTA. 43 The mean SSI values of our cohort were relatively high, being close to 60, and there was no significant difference among groups in terms of SSI values.…”

“…34,35 During the measurement of FAZ area and perimeter, Littmann's method was used to correct the ocular magnification by each AL. [34][35][36][37][38] Details of the formula are provided elsewhere. 34,35,37,38 In brief, the relationship between the measured OCTA image diameter, Dm, and the true diameter, Dt, can be formulated as Dt ¼ p*q*Dm, where p and q are the image magnification factor of the imaging system and the eye, respectively.…”

“…34,35,37,38 Thus, AL-related magnification factor can be corrected by Dt ¼ 3.460*0.01306*(AL À 1.82)*Dm. 34,35,37,38 Poor quality OCTA images were excluded from the analysis, including signal strength index (SSI) < 48 (minimum ¼ 1, maximum ¼ 100) 23,25,26,36,[39][40][41][42] ; poor-clarity images due to severe media opacities; motion artifacts or localized weak signal by vitreous floaters; residual motion artifacts visible as irregular vessel patterns or disc boundary on the en face angiogram; images not centered on the fovea for macular OCTA (fixation error); and segmentation failure.…”