Peripapillary microvasculature in the retinal nerve fiber layer in glaucoma by optical coherence tomography angiography: focal structural and functional correlations and diagnostic performance

The Role of Optical Coherence Tomography Angiography in Glaucoma

Glaucoma is the leading cause of irreversible vision loss and comprises a group of chronic optic neuropathies characterized by progressive retinal ganglion cell (RGC) loss. Various etiologies, including impaired blood supply to the optic nerve, have been implicated for glaucoma pathogenesis. Optical coherence tomography angiography (OCTA) is a non-invasive imaging modality for visualizing the ophthalmic microvasculature. Using blood flow as an intrinsic contrast agent, it distinguishes blood vessels from the surrounding tissue. Vessel density (VD) is mainly used as a metric for quantifying the ophthalmic microvasculature. The key anatomic regions for OCTA in glaucoma are the optic nerve head area including the peripapillary region, and the macular region. Specifically, VD of the superficial peripapillary and superficial macular microvasculature is reduced in glaucoma patients compared to unaffected subjects, and VD correlates with functional deficits measured by visual field (VF). This renders OCTA similar in diagnostic capabilities compared to structural retinal nerve fiber layer (RNFL) thickness measurements, especially in early glaucoma. Furthermore, in cases where RNFL thickness measurements are limited due to artifact or floor effect, OCTA technology can be used to evaluate and monitor glaucoma, such as in eyes with high myopia and eyes with advanced glaucoma. However, the clinical utility of OCTA in glaucoma management is limited due to the prevalence of imaging artifacts. Overall, OCTA can play a complementary role in structural OCT imaging and VF testing to aid in the diagnosis and monitoring of glaucoma.

Retinal Vascular Changes in Heart Failure with Preserved Ejection Fraction Using Optical Coherence Tomography Angiography

Background: Systemic microvascular regression and dysfunction are considered important underlying mechanisms in heart failure with preserved ejection fraction (HFpEF), but retinal changes are unknown. Methods: This prospective study aimed to investigate whether retinal microvascular and structural parameters assessed using optical coherence tomography angiography (OCT-A) differ between patients with HFpEF and control individuals (i.e., capillary vessel density, thickness of retina layers). We also aimed to assess the associations of retinal parameters with clinical and echocardiographic parameters in HFpEF. HFpEF patients, but not controls, underwent echocardiography. Macula-centered 6 × 6 mm volume scans were computed of both eyes. Results: Twenty-two HFpEF patients and 24 controls without known HFpEF were evaluated, with an age of 74 [68-80] vs. 68 [58-77] years (p = 0.027), and 73% vs. 42% females (p = 0.034), respectively. HFpEF patients showed vascular degeneration compared to controls, depicted by lower macular vessel density (p < 0.001) and macular ganglion cell-inner plexiform layer thickness (p = 0.025), and a trend towards lower total retinal volume (p = 0.050) on OCT-A. In HFpEF, a lower total retinal volume was associated with markers of diastolic dysfunction (septal e', septal and average E/e': R2 = 0.38, 0.36, 0.25, respectively; all p < 0.05), even after adjustment for age, sex, diabetes mellitus, or atrial fibrillation. Conclusions: Patients with HFpEF showed clear levels of retinal vascular changes compared to control individuals, and retinal alterations appeared to be associated with markers of more severe diastolic dysfunction in HFpEF. OCT-A may therefore be a promising technique for monitoring systemic microvascular regression and cardiac diastolic dysfunction.

Neurovascular segregation of the retinal nerve fiber layer in glaucoma

The imaging data of one eye from 154 healthy and 143 glaucoma participants were acquired to evaluate the contributions of the neuronal and vascular components within the retinal nerve fiber layer (RNFL) for detecting glaucoma and modeling visual field loss through the use of optical coherence tomography (OCT) and OCT angiography. The neuronal and vascular components within the circumpapillary RNFL were independently evaluated. In healthy eyes, the neuronal component showed a stronger association with age (r = -0.52, p < 0.001) compared to measured RNFL thickness (r = -0.46, p < 0.001). Using the neuronal component alone improved detection of glaucoma (AUC: 0.890 ± 0.020) compared to measured RNFL thickness (AUC: 0.877 ± 0.021; χ2 = 5.54, p = 0.019). Inclusion of the capillary components with the sectoral neuronal component resulted in a significant improvement in glaucoma detection (AUC: 0.927 ± 0.015; χ2 = 15.34, p < 0.001). After adjusting for potential confounders, AUC increased to 0.952 ± 0.011. Results from modeling visual field loss in glaucoma eyes suggest that visual field losses associated with neuronal thinning were moderated in eyes with a larger capillary component. These findings suggest that segregation of the neurovascular components could help improve understanding of disease pathophysiology and affect disease management in glaucoma.

Quantification of vascular morphology in optical coherence tomography angiography in primary open angle glaucoma

Purpose

To quantitatively measure and compare the vascular morphology in healthy eyes and eyes with primary open-angle glaucoma (POAG) using optical coherence tomography angiography (OCTA) scans.

Methods

This is a retrospective and cross-sectional study which include healthy individuals and individuals with POAG that underwent OCTA imaging at an academic center's glaucoma clinic. We analyzed OCTA scans of the macula and optic nerve head (ONH) of one eye from each subject to quantitatively measure vessel density (VD), vessel length density (VLD), and branchpoint density (BPD). We compared these 3 parameters between the healthy and POAG groups and used logistic regression classification models to determine their diagnostic value in differentiating healthy and glaucomatous eyes.

Results

We included 49 healthy subjects and 49 subjects with POAG. After age-adjusted analysis, the parameters of VD, VLD, and BPD were significantly reduced in eyes with POAG (P ​< ​0.001) in all scan layers and most significantly around the ONH. The parameter with the best performances were radial peripapillary capillary (RPC) VD [AUC (areas under the curve): 0.939 (0.891, 0.987)] which had statistically higher performances (P ​< ​0.05) than parameters in the superficial or deep layers. All 3 parameters in the RPC layer had statistically similar performances.

Conclusions

We found that VD, VLD, and BPD were reduced in glaucomatous eyes. The morphologic parameters of VLD and BPD had similar performances to the traditional parameter of VD in RPC layers. Our results suggest that vascular morphology parameters may provide additional value in the diagnosis and evaluation of glaucoma.

Comparative analysis of retinal photoplethysmographic spatial maps and thickness of retinal nerve fiber layer

The paper presents a comparative study of the pulsatile attenuation amplitude (PAA) within the optic nerve head (ONH) at four different areas calculated from retinal video sequences and its relevance to the retinal nerve fiber layer thickness (RNFL) changes in normal subjects and patients with different stages of glaucoma. The proposed methodology utilizes processing of retinal video sequences acquired by a novel video ophthalmoscope. The PAA parameter measures the amplitude of heartbeat-modulated light attenuation in retinal tissue. Correlation analysis between PAA and RNFL is performed in vessel-free locations of the peripapillary region with the proposed evaluating patterns: 360° circular area, temporal semi-circle, nasal semi-circle. For comparison, the full ONH area is also included. Various positions and sizes of evaluating patterns in peripapillary region were tested which resulted in different outputs of correlation analysis. The results show significant correlation between PAA and RNFL thickness calculated in proposed areas. The highest correlation coefficient Rtemp = 0.557 (p<0.001) reflects the highest PAA-RNFL correspondence in the temporal semi-circular area, compared to the lowest value in the nasal semi-circular area (Rnasal = 0.332, p<0.001). Furthermore, the results indicate the most relevant approach to calculate PAA from the acquired video sequences is using a thin annulus near the ONH center. Finally, the paper shows the proposed photoplethysmographic principle based on innovative video ophthalmoscope can be used to analyze changes in retinal perfusion in peripapillary area and can be potentially used to assess progression of the RNFL deterioration.

Correlation between OCT-angiography and photopic negative response in patients with primary open angle glaucoma

Purpose

To evaluate the association between OCT-angiography (OCTA) and photopic negative response (PhNR) in open angle glaucoma (OAG) patients and assess the diagnostic accuracy of these parameters in early detection of glaucoma.

Methods

A total of 152 eyes were enrolled in this study, 28 eyes with mild POAG (group I), 44 eyes with moderate-severe POAG (group 2) & 80 eyes of healthy subjects (control group). Full ophthalmological examination, OCTA and PhNR measurements were underwent for all participants. RNFL, GCC thicknesses, PhNR (implicit time and amplitude) were recorded. The superficial and deep capillary plexus vessel density (SCP-VD%, DCP-VD%) were measured by using 6 × 6 mm macula OCTA scans. The peripapillary vessel density (RPC-VD %) were measured by using 4.5 × 4.5 mm optic disk head OCTA scans.

Results

There were reduction of the median Interquartile range (IQR) thickness of the GCC and RNFL in OAG eyes versus normal (P < 0.001). RPC-VD%, SCP-VD % and DCP-VD% were significantly reduced in OAG eyes versus normal (P < 0.001). Increased OAG severity was associated with more reduction in PhNR amplitude and increased implicit time. Reduced PhNR amplitude and prolonged latency were significantly correlated with reduced vascular parameters. The RCP-VD and PhNR amplitude demonstrated higher diagnostic accuracy (98.7) with the largest AUC and higher sensitivity and specificity (100% & 98.7%, respectively), followed by the PhNR implicit time with (AUC = 0.995) with a diagnostic accuracy 98.7. The SCP-VD, RNFL and GCC thickness had a diagnostic accuracy of (75.0, 81.6 & 84.2), respectively (P < 0.001).

Conclusions

OCTA vascular parameters displayed significant positive correlation with PhNR amplitude and significant negative correlation with PhNR implicit time. OCTA and PhNR parameters showed a high diagnostic accuracy for detection of glaucoma, and both may provide promising insight in early detection of glaucoma.

This study was retrospectively registered on ClinicalTrials.gov (identifier, NCT05104294).

Lamina cribrosa curvature index: A reliable parameter to screen diabetic patients for glaucoma

PURPOSE

To compare the translaminar pressure difference (TLPD), anterior lamina cribrosa surface depth (ALCSD), lamina cribrosa thickness (LCT), lamina cribrosa curvature index (LCCI) and peripapillary vascular density (pVD) in diabetic and healthy subjects.

METHODS

Two hundred and eighty eyes of 140 patients (79 patients with diabetes mellitus (DM) without diabetic retinopathy (DR) and 61 healthy subjects) were enrolled in this study. Full ophthalmological examination, as well as optical coherence tomography (OCT) and OCT angiography (OCT-A) images, were analyzed. The ALCSD, LCT, LCCI were measured by enhanced depth imaging (EDI) OCT and the pVD by OCT-A. The TLPD values and relationships between TLPD and lamina cribrosa features and pVD were investigated in all subjects.

RESULTS

The ALCSD and LCT were significantly shallower and thinner in diabetic patients when compared to healthy subjects (p <0.001). There was no significant difference in the LCCI in diabetics 13.717 (5.74-33.91) vs healthy subjects 13.118 (5.53-27.05) (p = 0.181). OCT-A revealed that the pVD in the diabetic group was significantly lower than in the non-diabetic group (p <0.001). TLPD was significantly lower in diabetic patients compared to healthy controls.

CONCLUSION

There are early changes in pVD and peripapillary vessel morphology in patients with DM. ALCSD and LCT were shallower and thinner in diabetic patients whereas the LCCI did not differ significantly. LCCI may be more valuable in assessing the lamina cribrosa (LC) of diabetic patients. The TLPD was found to be lower in diabetic patients compared to normal controls.

The effect of postmenopausal hormonal drop on optic nerve head and peripapillary perfusion using optical coherence tomography angiography (OCTA)

We studied the effect of menopause with subsequent estrogen drop on optic nerve head structure and peripapillary vasculature. This cross-sectional analytic study was carried out on 100 eyes of 100 patients; patients were divided into a premenopausal group (50 eyes) and a postmenopausal group (50 eyes). Optical coherence tomography was done to evaluate retinal nerve fiber layer thickness (RNFLT) and optical coherence tomography angiography (OCTA) to assess the peripapillary capillary vessel density. RNFLT as well as the peripapillary vessel density (VD) were significantly lower in the postmenopausal group (P value < 0.001) with increasing age, hormonal drop, and higher intraocular pressure (IOP), specifically in the inferior quadrant. However, the negative correlation between IOP and VD (r = - 0.541) was stronger than its negative correlation with RNFLT (r = - 0.318). Postmenopausal hormonal changes lead to a significant rise in IOP-although still not glaucomatous- and a decrease in the RNFLT and perfusion of the optic nerve. This confirms the relation between hormonal drop and glaucoma in postmenopausal women. Changes in peripapillary vascular density were more evident than RNFL in correlation with IOP and age changes. So, OCTA can be used to detect early optic nerve affection.

Wedge Defects on Optical Coherence Tomography Angiography of the Peripapillary Retina in Glaucoma: Prevalence and Associated Clinical Factors

PRCIS

Among subjects with glaucoma, wedge-shaped defects on optical coherence tomography angiography (OCTA) were associated with disc hemorrhages (DH), paracentral visual field (VF) defects, increased cup-to-disc ratio (CDR), and thinner retinal nerve fiber layer (RNFL).

PURPOSE

To examine determinants of wedge defects on peripapillary OCTA in glaucoma.

MATERIALS AND METHODS

A total of 278 eyes of 186 subjects with mild to severe primary open-angle glaucoma underwent 6×6 spectral-domain OCTA imaging of the superficial peripapillary retina from 2016 to 2020 at an academic practice. Wedge defects were defined as focal microvasculature loss that extends outward from the optic nerve in an arcuate, wedge shape. Logistic regression models controlling for intereye correlation identified variables significantly associated with wedge defects. Eyes with profound microvasculature loss in both hemispheres were excluded. Candidate variables included: age, sex, race or ethnicity, diabetes, hypertension, follow-up duration, baseline untreated intraocular pressure, intraocular pressure at time of imaging, DH history, paracentral VF defects, CDR, central corneal thickness, spherical equivalent, VF mean deviation, RNFL thickness, and glaucoma stage.

RESULTS

Of 278 eyes, 126 (45.3%) had wedge defects in at least 1 hemisphere. In our multivariable logistic regression model, wedge defects were associated with DH history [odds ratio (OR): 3.19, 95% confidence interval (CI): 1.05-9.69, P=0.041], paracentral VF defects [OR: 4.38 (95% CI: 2.11-9.11), P<0.0001], larger CDR [OR: 1.27 (95% CI: 1.03-1.56), P=0.024, per 0.1 increase], and thinner RNFL [OR: 1.71 (95% CI: 1.25-2.34), P=0.0009, per 10 μm decrease].

CONCLUSION

DH history and paracentral VF defects were independently associated with wedge defects on OCTA, which was present in 45.3% of primary open-angle glaucoma patients. These findings may provide insight into glaucoma pathogenesis.

OCT angiography, RNFL and the visual field at different values of intraocular pressure

The aim of the present study was to investigate the relationship between intraocular pressure (IOP), vessel density (VD), retinal nerve fiber layer (RNFL) parameters and overall defect (OD) of the visual field in eyes where antiglaucoma treatment had not yet been initiated. A total of 61 subjects (122 eyes) who had an IOP of >20 mmHg on several occasions, in at least one eye, in routine outpatient care were included. These were subjects who had never been treated for hypertension glaucoma. The cohort was divided into four subgroups. In the first group, there were 18 eyes with an IOP value of <20 mmHg. In the second group, there were 39 eyes with IOP values of 20-22 mmHg. The third group consisted of 32 eyes with IOP values of 22-24 mmHg and the final group consisted of 33 eyes with IOP values of >24 mmHg. The IOP results were compared with VD, RNFL and OD using Pearson's correlation coefficient to assess the relationship between the selected parameters. RNFL and OD were moderately correlated only in the group of eyes with an IOP value >24 (r=0.48); in the other groups the correlation was very weak. However, changes in visual field were already observed in eyes with IOP 20-22 mmHg (r=-0.27). There was a moderate correlation in eyes with an IOP value >24 mmHg (r=-0.53). The most significant result observed was the relationship between VD and RNFL. In eyes with an IOP value ≤20, a moderate to strong correlation between these parameters was observed. This relationship increased with increasing IOP values up to a very strong correlation in the group with an IOP value >24 mmHg. A moderate to strong dependence between VD and RNFL in eyes with an IOP value ≤20 mmHg was observed, and this dependence was very strongly correlated in the eyes with an IOP value >24 mmHg.

Comparison of the Structure-Function Relationship in Glaucoma Using Optical Microangiography in the Peripapillary Retinal Nerve Fiber Layer

PRCIS

Optical microangiography measurements correlated with functional parameters in glaucoma patients. Optical coherence tomography angiography-derived vessel perfusion density (VPD) better reflected the structure-function relationship than flux index (FI) and retinal nerve fiber layer thickness.

PURPOSE

The purpose of this study was to compare the structure-function relationship between peripapillary optical microangiography (OMAG) measurements and standard automated perimetry (SAP) loss by comparison with peripapillary retinal nerve fiber layer (pRNFL) thickness in primary open-angle glaucoma.

MATERIALS AND METHODS

One eye from each of 128 patients with early-to-severe glaucoma (including preperimetric glaucoma) and 23 normal participants underwent optic nerve head scanning of the radial peripapillary capillaries and pRNFL scans with OMAG centered on the optic disc and SAP (mean age: 67.8±12.0 y; SAP mean deviation: -5.84±6.6 dB). Regional relationships between VPD, FI, pRNFL thickness, and corresponding SAP sensitivity were compared using linear and fractional polynomial (FP) models.

RESULTS

Structure was significantly related to function for all but the nasal pRNFL thickness region. For VPD, the coefficient of determination (R2) using the FP model was significantly stronger than that of the linear model (FP: 0.25 to 0.67, linear: 0.19 to 0.61), while no difference was found for FI in any region (FP: 0.19 to 0.44, linear: 0.15 to 0.42). R2 for VPD was stronger than FI and pRNFL (FP: 0.11 to 0.52, linear: 0.01 to 0.44) in inferior and superior regions, while VPD and FI were not different in temporal and nasal regions.

CONCLUSIONS

VPD showed a stronger association with visual field loss than FI or retinal nerve fiber layer thickness except in the temporal region. The FI relationship was weak but more linear around the peripapillary region. The strength of the structure-function relationship may differ depending on the region of OMAG measurements.

Optic disc cupping after circumpapillary Pd-103 slotted plaque radiation therapy

OBJECTIVE

To investigate vascular and morphologic optic disc changes after slotted plaque radiation therapy for choroidal melanoma involving the optic disc.

DESIGN

Retrospective cross-sectional study.

PARTICIPANTS

Thirty-nine patients with choroidal melanoma involving the optic nerve.

METHODS

Each melanoma was treated with palladium-103 slotted plaque brachytherapy (incorporating and/or surrounding the optic nerve sheath) between 2005 and 2019. Imaging of the optic nerve before and after radiation allowed for documentation and evaluation of optic nerve pallor and cup-to-disc ratio (CDR) changes. Optical coherence tomography (OCT) CDR measurements and intraocular pressure (IOP) were recorded pretreatment and at follow-up. Of these patients, 22 also had OCT angiography (OCT-A) images with sufficient quality for evaluation of blood vessel density and length. Differences in cup-to-disc measurements were correlated with changes in OCT-A-measured vessel density and length.

RESULTS

Following slotted plaque radiation therapy, there was no significant increase in IOP or optic nerve pallor. OCT and colour photography revealed significant increases (both p < 0.001) in CDR from pretreatment to the last follow-up. Increased CDRs on OCT were significantly correlated to OCT-A-measured change in vessel length (p = 0.027). Similarly, increased CDR ratios on fundus photography were significantly correlated with OCT-A-measured change in vessel density (p = 0.043) and length (p = 0.019).

CONCLUSION

Fundus photography and OCT measurements revealed increased optic disc cupping following slotted plaque radiation therapy. Cupping was associated with OCT-A evidence of synchronous progressive peripapillary vascular occlusion and attenuation. Therefore, slotted plaque radiation-induced peripapillary and papillary ischemia was associated with increased CDR ratios and optic disc cupping.

Steps to Measurement Floor of an Optical Microangiography Device in Glaucoma

PURPOSE

To compare dynamic ranges and steps to measurement floors of peripapillary and macular metrics from a complex signal-based optical microangiography (OMAG^C) optical coherence tomography angiography (OCTA) device for glaucoma with those of OCT measurements.

DESIGN

Cross-sectional study.

METHODS

Imaging of 252 eyes from 173 patients with glaucoma and 123 eyes from 92 subjects without glaucoma from a glaucoma clinic was quantified using custom and commercial software. Metrics from OCT (retinal nerve fiber layer [RNFL], ganglion cell/inner plexiform layer [GCIPL]) and OCTA (custom: peripapillary vessel area density [pVAD], macular vessel area density [mVAD], and macular vessel skeleton density [mVSD]; commercial: peripapillary perfusion density [pPD^Z], macular perfusion density [mPD^Z], and macular vessel density [mVD^Z]) were plotted against visual field mean deviation (MD) with linear change-point analyses, measurement floors, and steps to floors.

RESULTS

Mean MD (dB) for glaucomatous eyes was -5.77 (-6.45 to -5.10). The number of eyes with mild glaucoma (MD >-6), moderate glaucoma (MD -6 to -12), and severe glaucoma (MD <-12) were 164, 50, and 38, respectively. pPD^Z yielded the lowest estimated floor at -26.6 dB (standard error [SE] 1.53), followed by OCTA macular metrics (-25 to -21 dB; SE 1.03) and pVAD (-17.6 dB, SE 1.06). RNFL and GCIPL produced floors at -17.8 (SE 0.927) and -23.6 dB (SE 1.14). The highest number of steps to measurement floor belonged to RNFL (7.20) and GCIPL (7.33), followed by pPD^Z (4.25), mVAD (3.87), and mVSD (3.81), with 2.5 or fewer steps for pVAD, mPD^Z, and mVD^Z.

CONCLUSIONS

pPD^Z, mVAD, and mVSD had approximately 4 steps within their dynamic ranges, without true measurement floors, and thus may be useful in evaluating advanced glaucomatous progression. Improving OCTA test-retest repeatability could augment number of steps for OCTA metrics, increasing their clinical utility.

Retinal Microcirculatory Responses to Hyperoxia in Primary Open-Angle Glaucoma Using Optical Coherence Tomography Angiography

Purpose

To investigate the retinal vascular response to hyperoxia in patients with primary open-angle glaucoma (POAG) using optical coherence tomography angiography (OCTA).

Methods

This prospective study included 27 eyes in 27 patients with POAG and 14 eyes in 14 age- and sex-matched healthy participants. Retinal radial peripapillary capillary (RPC) perfusion was measured by OCTA before and after inhaling oxygen in all participants. Systemic hemodynamic variables were also examined and recorded before and after hyperoxia.

Results

Hyperoxia significantly reduced the perfused vessel density (PVD) of RPCs in both healthy controls (baseline and hyperoxia: 54.2 ± 4.1 and 51.0 ± 4.4, respectively, P < 0.001) and patients with POAG (baseline and hyperoxia: 44.7 ± 6.1 and 43.2 ± 5.4, respectively, P = 0.001). However, the changes in peripapillary PVD between the two gas conditions in patients with POAG were significantly lower than in healthy controls, including both the absolute change (baseline-hyperoxia: 1.5 ± 2.0 and 3.2 ± 1.2, respectively, P = 0.006) and relative change (ratio of absolute change and baseline value: 3.0% ± 4.6% and 6.0% ± 2.4%, respectively, P = 0.04).

Conclusions

Retinal microvasculature responds to hyperoxia by reducing RPC perfusion in both healthy participants and patients with POAG. However, this vasoreactivity capacity was significantly impaired in patients with POAG.

Hemiretinal Asymmetry in Peripapillary Vessel Density in Healthy, Glaucoma Suspect, and Glaucoma Eyes

PURPOSE

To investigate hemiretinal asymmetry in radial peripapillary capillary vessel area density (VAD) of healthy, glaucoma suspect, and glaucoma eyes of varying severity and its diagnostic utility for glaucoma.

DESIGN

Population-based, cross-sectional study.

METHODS

Optic disc scans (6 × 6 mm) were collected on optical coherence tomography angiography (OCTA) to obtain VAD and on optical coherence tomography (OCT) to measure circumpapillary retinal nerve fiber layer (RNFL) thickness. Hemiretinal difference in VAD (hdVAD) was defined as the absolute difference between superior and inferior hemiretinal VAD. Age-adjusted multivariable linear regression of hdVAD on glaucoma severity was performed. Areas under curves (AUCs) were calculated from predicted probabilities generated by multiple logistic regression of glaucoma severity on age-adjusted single and combined parameters.

RESULTS

A total of 1,043 eyes of 1,043 participants (587 healthy, 270 suspect, 67 mild, 54 moderate, 65 severe glaucoma) were included. After age adjustment, mean hdVAD was similar between healthy and suspect (P = .225), higher in mild vs suspect (P < .001), and higher in moderate vs mild (P = .018), but lower in severe vs moderate (P = .001). AUCs of hdVAD were highest for discriminating mild (0.685) and moderate (0.681) glaucoma from healthy. Combining hdVAD and global RNFL (gRNFL) yielded the highest AUCs of all parameters for mild (0.818) and any POAG (0.859) and resulted in significantly better diagnostic accuracy than either hdVAD or gRNFL alone (P < .05 for all comparisons).

CONCLUSIONS

hdVAD is higher in early glaucoma and may help with early detection when damage is focal, but its diagnostic ability appears less robust in advanced glaucoma when damage is diffuse.

Relationship Between Macular Vessel Density and Total Retinal Blood Flow in Primary Open-angle Glaucoma

PRECIS

An association between macular vessel density (VD) and total retinal blood flow (TRBF) was demonstrated in subjects with primary open-angle glaucoma (POAG) and visual field (VF) loss.

PURPOSE

The purpose of this study was to report relationships of macular VD metrics and TRBF in POAG.

MATERIALS AND METHODS

A total of 24 POAG and 19 healthy control subjects participated in the study. Subjects underwent optical coherence tomography and angiography for measurements of inner retinal thickness (IRT), VD, and spacing between large vessels (SLV) and small vessels (SSV). Doppler optical coherence tomography imaging was performed for TRBF measurement. In POAG subjects, automated perimetry was performed and VF loss expressed as mean deviation was measured.

RESULTS

Compared with the control group, POAG group had decreased VD, TRBF, IRT, and increased SLV (P<0.0001). Decreased VD (Pearson correlation, r=0.51; P<0.0001; N=43) and increased SLV (Spearman correlation, rs=-0.47; P=0.001) were correlated with decreased TRBF. Decreased VD and SSV (r≥0.39; P≤0.001; N=43) and increased SLV (rs=-0.71; P<0.0001) were associated with decreased IRT. Decreased VF mean deviation was correlated with decreased VD, SSV, IRT (r≥0.53; P≤0.001; N=24), and with increased SLV (rs=-0.84; P<0.0001).

CONCLUSIONS

The finding of an association between macular VD and TRBF supports the role of vascular factors in the pathophysiology of POAG and potential conduct of future studies aimed at identifying multiple image-based vascular metrics for disease diagnosis.

Longer Axial Length Potentiates Relationship of Intraocular Pressure and Peripapillary Vessel Density in Glaucoma Patients

Purpose

The purpose of this study was to investigate how axial length (AL) changes the relationship of intraocular pressure (IOP) with peripapillary vessel density (pVD) in glaucoma versus non-glaucomatous eyes.

Methods

A population-based, cross-sectional study of 2127 African Americans aged 40 years and older in Inglewood, California, were imaged with 6 × 6-mm optic disc optical coherence tomography angiography scans. There were 1028 healthy subjects (1539 eyes) and 65 subjects with glaucoma (86 eyes) who met inclusion criteria. A multivariable linear mixed effects regression model investigated the relationship of IOP on pVD after controlling for signal strength, retinal nerve fiber layer thickness, and age. These results were stratified by AL groups.

Results

Higher IOP was a significant predictor of lower pVD among subjects with glaucoma (P = 0.009), but not among healthy subjects (P = 0.26). After stratifying by the sample median AL (23.46 mm), higher IOP was associated with lower pVD among subjects with glaucoma with longer AL (≥ 23.46 mm, P = 0.005), but not among those in the shorter AL (< 23.46 mm, P = 0.45). IOP was not significantly associated with pVD among healthy subjects in either AL stratum.

Conclusions

Among subjects with glaucoma with longer AL, IOP was significantly associated with pVD. This relationship was not seen among subjects with glaucoma with shorter AL or non-glaucomatous subjects in either AL group. These findings support the hypothesis that disturbed retinal autoregulation may be present in subjects with glaucoma with longer AL. Longitudinal studies are needed to further investigate whether axial elongation increases glaucoma risk by compromising retinal autoregulation.

Paired Optic Nerve Microvasculature and Nailfold Capillary Measurements in Primary Open-Angle Glaucoma

Purpose

To assess microvascular beds in the optic nerve head (ONH), peripapillary tissue, and the nailfold in patients with primary open-angle glaucoma (POAG) versus controls.

Methods

Patients with POAG (n = 22) and controls (n = 12) underwent swept-source optical coherence tomography angiography of ophthalmic microvasculature and nailfold video capillaroscopy of the hand. The main outcomes were vessel density (VD) and blood flow of the ONH, the peripapillary and the nailfold microvasculatures.

Results

Patients with POAG were younger than controls (63.5 ± 9.4 vs. 69.9 ± 6.5 years, P = 0.03). Deep ONH VD and blood flow were lower in patients with POAG than controls (39.1% ± 3.5% vs. 43.8% ± 5.7%; 37.8% ± 5.3% vs. 46.0% ± 7.8%, respectively, P < 0.02 for both); similar results were observed with peripapillary VD (37.9 ± 2.6%, 43.4 ± 7.6%, respectively, P = 0.03). Nailfold capillary density and blood flow were lower in patients with POAG than controls (8.8 ± 1.0 vs. 9.8 ± 0.9 capillaries/mm; 19.9 ± 9.4 vs. 33.7 ± 9.8 pL/s, respectively; P < 0.009 for both). After adjusting for age and gender, deep ONH VD and blood flow, peripapillary VD, and nailfold capillary blood flow were lower in POAG than controls (β = −0.04, −0.07, −0.05, −13.19, respectively, P ≤ 0.046 for all). Among all participants, there were positive correlations between deep ONH and nailfold capillary blood flow (Pearson's correlation coefficient r = 0.42, P = 0.02), peripapillary and nailfold capillary density (r = 0.43, P = 0.03), and peripapillary and nailfold capillary blood flow (r = 0.49, P = 0.01).

Conclusions

Patients with POAG demonstrated morphologic and hemodynamic alterations in both ophthalmic and nailfold microvascular beds compared to controls.

Translational Relevance

The concomitant abnormalities in nailfold capillaries and relevant ocular vascular beds in POAG suggest that the microvasculature may be a target for POAG treatment.

Circumpapillary optical coherence tomography angiography differences in perimetrically affected and unaffected hemispheres in primary open-angle glaucoma and the preperimetric fellow eye

Purpose:

Evaluation of circumpapillary vessel density (VD) and perfusion density (PD) on optical coherence tomography angiography (OCTa) in mild-moderate glaucoma patients having unilateral visual field defects, with their fellow eyes and controls.

Methods:

Both eyes of 24 patients having a definitive nasal step or arcuate scotoma in one hemisphere of one eye only, and 24 controls, underwent OCTa.

Results:

In eyes with a superior field defect, the superior/inferior quadrant ratios, (SQ/IQ) of 3 mm scan of VD and PD were significantly higher in eyes with a superior arcuate scotoma than fellow eyes (P = 0.03,0.02) as also controls, (P = 0.004,0.001). The mean percentage loss of inferior quadrant VD between control to fellow eyes, and superior nasal step eyes were similar, 20.19%/19.57% respectively, P = 0.85, while a loss in arcuate scotoma eyes was 38.81% (P = 0.001). The percentage decrease in inferior quadrant PD in fellow eyes was 14.70%, superior nasal step 23.39%, and an arcuate scotoma 34.74% (P = 0.02). Eyes with a superior nasal step had significantly lower VD and PD absolute values in the inferior quadrant OCTa in 3 mm and 6 mm circle scan only as compared to control eyes, VD, P = 0.03,0.04/PD, P = 0.008,0.02. Fellow eyes of superior field defects had significantly lower VD and PD absolute values in the inferior quadrant in 3 mm and 6 mm circle scan as compared to control eyes, VD, P = 0.006,0.04/PD, P = 0.01,0.03. Eyes with an isolated inferior field defect in only one eye, showed a significant decrease in both VD and PD in all quadrants as compared to fellow eyes and control eyes. A significant positive correlation was found between VD and RNFL thickness in peripapillary superior unaffected quadrants in eyes with superior field defects and inferior unaffected quadrants in inferior defects (P = 0.001 and 0.01).

Conclusion:

There was a statistically significant increasing SQ/IQ ratio and percentage loss of vascular parameters from control to fellow eyes, those with a superior nasal step, and those with a superior arcuate scotoma. Inferior VFDs appeared to be associated with a more generalized circulatory loss. The asymmetry between hemispheres and between eyes could be used as a biomarker for early glaucomatous neuropathy.

Topographic Quadrant Analysis of Peripapillary Superficial Microvasculature in Optic Disc Drusen

Background: Limited information is known about the topographic effect of optic disc drusen (ODD) on peripapillary retinal nerve fibers and microvasculature. Objective: This study aims to understand the structural and functional impact of ODD in different quadrants of the optic disc. Methods: We performed a retrospective case-control study of 22 ODD patients (34 eyes) and 26 controls (33 eyes) to compare optical coherence tomography (OCT) retinal nerve fiber layer (RNFL), OCT angiography (OCTA), and corresponding static perimetry mean deviation (MD) calculated using the modified Garway-Heath map in different quadrants of the optic disc. OCTA was analyzed using custom MATLAB script to measure six parameters in a peripapillary annulus with large vessel removal: vessel area density (VAD), vessel skeleton density (VSD), vessel perimeter index (VPI), vessel complexity index (VCI), flux, and vessel diameter index (VDI). Results: Quadrant analysis revealed that OCTA VAD and VCI were significantly decreased in superior, nasal, and inferior but not temporal quadrant. RNFL, VSD, and VPI were significantly impacted only in the superior and nasal quadrants. Corresponding visual field MDs in all ODD eyes were not different in the four quadrants, although eyes with MD equal or worse than -5 dB (32%) had worst visual field corresponding to the superior quadrant of the optic disc (inferior arcuate visual field). Structure-structure comparison of OCT and OCTA showed high correlation of RNFL with multiple OCTA measurements in the superior, nasal, and inferior quadrants but not temporal quadrant. Structure-function analysis revealed significant correlation of VAD and VCI and visual field MD in every quadrant, but RNFL was only significantly correlated in the superior and inferior quadrants. Conclusions: Peripapillary VAD and VCI are decreased in more quadrants than RNFL, supporting the clinical utility of performing OCTA in addition to OCT. Consistent with the most common locations of ODD, five OCT/OCTA measurements (VAD, VCI, RNFL, VSD, VPI) are decreased in the superior and nasal quadrants. OCT/OCTA measurements were significantly impacted in contrast to the relatively mild effect on corresponding visual field MD, consistent with the idea that a decrease in objective structural and vascular measurements occurs without parallel change in subjective visual function in ODD.

Focal Structure-Function Relationships in Primary Open-Angle Glaucoma Using OCT and OCT-A Measurements

Purpose

To evaluate the focal structure-function associations among visual field (VF) loss, optical coherence tomography angiography (OCT-A) vascular measurements, and optical coherence tomography (OCT) structural measurements in glaucoma.

Methods

In this cross-sectional study, subjects underwent standard automated perimetry, OCT-based nerve fiber thickness measurements, and OCT-A imaging. Mappings of focal VF test locations with OCT and OCT-A measurements were defined using anatomically adjusted nerve fiber trajectories and were studied using multivariate mixed-effects analysis. Segmented regression analysis was used to determine the presence of breakpoints in the structure-function associations.

Results

The study included 119 eyes from 86 Chinese subjects with primary open-angle glaucoma (POAG). VF mean deviation was significantly associated with global capillary perfusion density (β = 0.13 ± 0.08) and global retinal nerve fiber layer thickness (β = 0.09 ± 0.02). Focal capillary density (FCD) was significantly associated with VF losses at 34 VF test locations (66.7% of 24-2 VF), with 24 of the 34 locations being within 20° of retinal eccentricity. Focal nerve layer (FNL) thickness was significantly associated with 16 VF test locations (31.4% of 24-2 VF; eight locations within 20° eccentricity). For VF test locations in the central 10° VF, VF losses below the breakpoint were significantly associated with FCD (slope, 0.89 ± 0.12, P < 0.001), but not with FNL thickness (slope, 0.57 ± 0.39, P = 0.15).

Conclusions

Focal capillary densities were significantly associated with a wider range of visual field losses and in a larger proportion of the visual field compared to nerve fiber thickness.

Optical Coherence Tomography for Ophthalmology Imaging

Optical coherence tomography (OCT) is a depth-resolved imaging modality, which is able to achieve micrometer-scale resolution within biological tissue noninvasively. In the past 30 years, researchers all around the world had made several essential efforts on techniques relevant to OCT. OCT has become a routine process for eye diseases with different types. In this chapter, the three important stages in the development of OCT are briefly illustrated, including the time domain OCT (TD-OCT), the frequency domain OCT (FD-OCT) and the optical coherence tomography angiography (OCTA). Each of the technique has made great progress for use on living human eye imaging in clinical applications. TD-OCT was first proposed and commercialized, which is able to achieve acceptable 2D depth-resolved cross-sectional images of human retina in vivo. FD-OCT was the upgraded OCT technique compared with TD-OCT. By capturing the coherent signal within the Fourier space, the FD-OCT could improve the image sensitivity compared with TD-OCT, and achieve dozens of kilo hertz imaging speed. OCTA is the newest developments of OCT technique, which is able to visualize the micro vasculature networks of human retina in vivo. With OCTA technique, the newest ophthalmologic OCT system is able to achieve detailed diagnosis for both micro-structure and vasculature abnormalities for clinical applications. The further development of OCT technique on imaging speed, contrast, resolution, field of view, and so on will make OCT to be a more powerful tool for clinical usages.

Quantitative Handheld Swept-Source Optical Coherence Tomography Angiography in Awake Preterm and Full-Term Infants

Purpose

To compare retinal vascular parameters acquired by handheld swept-source optical coherence tomography angiography (SS-OCTA) between nonsedated preterm and full-term infants.

Methods

Preterm and full-term infants at the University of Washington Medical Center were enrolled. Retinal angiograms (nominal size ∼7 × 7 mm²) were obtained at each routine retinopathy of prematurity (ROP) screening session for preterms and once during the first 72 hours of life for full-terms. Macular vessel area density and nonperfusion area were evaluated on the binarized vasculature map in both small (1.5 × 1.5 mm) and large (3 × 3 mm) quadrants. Average vessel diameter and tortuosity values were obtained from each large vessel branch (length >200 µm). All vascular analyses used previously published algorithms.

Results

Handheld SS-OCTA captured 31 of 55 (56%) high-quality volumes on 8 awake preterm infants (gestational age 28 ± 4 weeks, birth weight 891 ± 314 g, postmenstrual age at first imaging session 37 ± 2 weeks) and 48 of 54 (89%) volumes on 12 awake full-term infants (gestational age 39 ± 1 weeks, birth weight 3405 ± 329 g). Signal-to-noise ratio was 5.08 ± 1.52 dB in preterm and 4.90 ± 1.12 dB in full-term infants. Preterm infants had higher mean large vessel tortuosity compared to full-term infants (P = 0.004). The large nasal quadrant vessel area density of infants with stage 3 and/or pre-plus or worse ROP was higher than other preterm infants (P = 0.007).

Conclusions

Although inadequate image quality limited usable imaging sessions, handheld SS-OCTA achieved adequate signal-to-noise ratio in nonsedated infants for quantitative retinal vascular parameter analysis.

Translational Relevance

Large- and small-vessel parameters were associated with prematurity and ROP severity, respectively.

Optical coherence tomography angiography and the visual field in hypertensive and normotensive glaucoma

BACKGROUND

Hypertensive glaucoma (HTG) causes damage to the retinal ganglion cells and eventually to the entire visual pathway due to high intraocular pressure (IOP). However, increased IOP will also affect the vessel density (VD) of the posterior pole of the eye and the related retinal ganglion nerve fibres (RNFL). In normotensive glaucoma (NTG), the retinal ganglion cells are relatively intact. The pathology is at the level of ganglion fibres. The unanswered question is what has altered ganglion cell fibres at the level of the retina and optic nerve head in NTG?

AIM

The aim of this study was to determine whether there is a correlation between the retinal nerve fibre layer (RNFL) and vessel density (VD) at the same altitudinal half of the retina and the sum of sensitivities of the contralateral half of the visual field of the same eye in hypertensive and normotensive glaucoma (NTG).

METHODS

Our group included 20 patients with HTG and 20 patients with NTG. The Pearson's correlation coefficient r was used for evaluation of the relationship of the peripapillary RNFL and VD, visual field (using the fast threshold glaucoma program) as the sum of sensitivities in apostilbs (asb) to the extent of 0-22 degrees. The results of sensitivity were compared with the RNFL and VD of the contralateral altitudinal half of the retina in the same eye.

RESULTS

In the HTG group there was a moderate relationship between RNFL and VD (both hemifields), but no relationship between RNFL and VF. VD SH and VF IH showed weak correlation and VD IH and VF SH showed no correlation. In patients with NTG, we found a strong correlation between RNFL and VD (both hemifields), between VD SH and VF IH a moderate correlation, between VD IH and VF SH also a moderate correlation and a weak correlation between RNFL and VF.

CONCLUSION

By comparing the RNFL and VD at the same altitudinal halves of the retina, we found a moderate correlation in HTG and a strong correlation in NTG. We found no or a weak correlation between VD and VF in HTG. In NTG the relationship between VD and VF showed a strong correlation. These findings reveal the differences in the diagnostic groups.

Vision Loss in Optic Disc Drusen Correlates With Increased Macular Vessel Diameter and Flux and Reduced Peripapillary Vascular Density

PURPOSE

To determine the key optical coherence tomography (OCT) and OCT angiography (OCTA) parameters that correlate with visual field loss in optic disc drusen (ODD).

DESIGN

Retrospective cross-sectional study.

METHODS

Single academic center. Seventeen patients with ODD (29 eyes) and 35 age-matched controls (53 eyes). Static perimetry, OCT, and OCTA imaging of optic disc and macula. Static perimetry, OCT, and OCTA measurements.

RESULTS

We investigated the relationship between static perimetry and 14 OCT/OCTA measurements in patients with ODD vs age-matched controls and found 5 key measurements that most correlated with visual field loss included: peripapillary retinal nerve fiber layer (RNFL), macular ganglion cell complex (GCC), peripapillary vessel area density (VAD), macular vessel diameter (VD), and flux. Hierarchical clustering of these 5 measurements vs all clinical characteristics revealed 3 distinct clusters. ODD and control eyes with no visual field loss (mean deviation [MD] > -2.0 dB) had high RNFL and GCC, and low macular VD and flux. ODD eyes with mild visual field loss (MD -2.0 to -5.0 dB) had high RNFL, GCC, and increased macular VD and flux. ODD eyes with moderate/severe visual field loss (MD < -5.0 dB) had decreased RNFL, GCC, peripapillary VAD, and increased macular VD and flux.

CONCLUSIONS

OCT and OCTA provided objective measurements that can help predict visual field loss in ODD. Our data suggest that increased macular flow may be an early biomarker of visual field loss in ODD, while decreased peripapillary vessel density and RNFL thickness are late biomarkers of visual field loss in ODD.

Quantitative analysis of astrocyte and axonal density relationships: Glia to neuron ratio in the optic nerve laminar regions

Astrocytes are critical for the maintenance of retinal ganglion cell (RGC) axonal function and viability, and form a key component of the functional neurovascular unit. Recently, we described the quantitative properties of astrocytes in relation to the capillary distributions in optic nerve laminar regions. Here, we provide a quantitative analysis of astrocytes and RGC axons in longitudinal sections of optic nerve tissue. Histological and immunocytochemical techniques are used to demonstrate the density of astrocytes, RGC axons and glia-neuron ratios across the pre laminar, lamina cribrosa and post laminar compartments of the optic nerve head (ONH). A study of human, pig, horse and rat optic nerves was performed and comparisons are made between species. This study demonstrates that the distribution of astrocytes correlates closely with the density of axonal processes, in accordance with the functional requirement of different regions of the ganglion cell axon. There was a consistency of glia-neuron ratios in the majority of laminar compartments, except for the human and rat prelaminar regions, which demonstrated lower ratios of astrocyte to axonal processes. The distribution of astrocytes may reflect a functional susceptibility to development of disease in the prelaminar region of the optic nerve. Interspecies comparison at the lamina cribrosa showed strikingly consistent glia-neuron ratios. Collectively, our findings suggest there may be a critical ratio of glia to neuron needed to maintain healthy cellular physiology across different laminar compartments of the optic nerve, with particular importance for the health of the lamina cribrosa region. It is possible that, in disease processes, the glia-neuron relationships across the different laminar compartments may be perturbed and this may be relevant for the development of glaucoma. Emerging technologies may further aid our understanding in how the physiology of optic nerve tissue cellular structure may be affected by changes to ONH characteristics and elevated intraocular pressure induced damage. Such findings may also permit the early identification of RGC axonal injury by identifying quantifiable changes in structural tissue architecture when pathophysiological pathways predominate.

Effect of Scan Size on Glaucoma Diagnostic Performance Using OCT Angiography En Face Images of the Radial Peripapillary Capillaries

PRECIS

When comparing 4.5×4.5 mm to 6.0×6.0 mm optical coherence tomography angiography scans of the radial peripapillary capillaries (RPCs) for glaucoma diagnostic capability, there was a trend of 4.5 scans outperforming 6.0 scans, especially for inferior, nasal, and superior quadrants.

OBJECTIVES

The main purpose of this study was to compare diagnostic ability of peripapillary vessel parameters from 4.5×4.5 mm (4.5) and 6.0×6.0 mm (6.0) spectral-domain optical coherence tomography angiography scans of the RPC in detecting primary open-angle glaucoma from nonglaucoma eyes.

METHODS

Consecutive patients from an academic glaucoma clinic underwent 4.5 and 6.0 scans (CIRRUS HD-OCT 5000 with AngioPlex OCT Angiography; ZEISS, Dublin, CA). Automatic segmentation created en face RPC images. Vessel area density, vessel skeleton density, and flux were calculated using custom quantification software, and perfusion density and flux index (FI) using automated quantification software. Area under the curve statistics included age and hypertension in the analysis.

RESULTS

Of 173 eyes from 123 patients who underwent both 4.5 and 6.0 imaging, 32 primary open-angle glaucoma eyes from 32 patients and 95 nonglaucoma eyes from 95 patients were studied. For the global region of 4.5 versus 6.0 scans, area under the curve was 0.940 and 0.916 for vessel area density (P=0.286); 0.941 and 0.921 for vessel skeleton density (P=0.385); 0.942 and 0.916 for flux (P=0.239); 0.912 and 0.884 for perfusion density (P=0.103); and 0.913 and 0.865 for FI (P=0.159), respectively. For the quadrant regions, 4.5 images significantly outperformed 6.0 images for the superior and inferior quadrants for flux and superior and nasal quadrants for FI (P-values=0.007, 0.047, 0.011, 0.007, respectively); other quadrant differences were not significant.

CONCLUSIONS

Parameters from 4.5 scans generally outperformed those from 6.0 scans in the global and quadrant regions, suggesting greater digital resolution in 4.5 scans of the immediate peripapillary RPC is important in detecting glaucomatous changes.

Clinical Utility of Triplicate En Face Image Averaging for Optical Coherence Tomography Angiography in Glaucoma and Glaucoma Suspects

PRéCIS:: Averaging triplicate en face angiograms of the radial peripapillary capillary (RPC) plexus with optical coherence tomography angiography (OCTA) improves vessel visualization, reduces vessel density parameters, and increases the diagnostic accuracy for glaucoma of one such parameter.

PURPOSE

The purpose of this study was to test the hypothesis that triplicate averaging of the RPC layer improves visualization and diagnostic accuracy of OCTA for glaucoma.

MATERIALS AND METHODS

This is a cross-sectional study involving 63 primary open-angle glaucoma patients and 70 age-matched glaucoma suspects. Triplicate 6×6 mm OCTA scans of the optic nerve head were acquired, and the RPC layer was extracted. RPC en face images were registered and averaged. Parameters of global entropy, global standard deviation, local texture correlation, local homogeneity, signal-to-noise ratio, and intercapillary distance were used to measure the change in visualization with averaging. Vessel area density (VAD), vessel skeleton density (VSD), and flux parameters were calculated in a 2.8 mm annulus excluding the optic disc. The diagnostic accuracy of these parameters for glaucoma was assessed by calculating the area under the receiver operating curve (AUC) values.

RESULTS

Three-frame averaging resulted in decreased global entropy and global standard deviation (Ps<0.001), and increased local texture correlation, local homogeneity, signal-to-noise ratio, and intercapillary distance (Ps<0.001). Averaged images also had reduced VAD, VSD, and flux (Ps<0.001). AUC was significantly increased for VSD after image averaging (P=0.018), while no significant change in AUC was observed for VAD (P=0.229) or flux (P=0.193).

CONCLUSIONS

Triplicate averaging improves visualization of the RPC layer and the diagnostic accuracy of VSD for glaucoma. The impact of image averaging on OCTA diagnostic performance and other potential applications warrants further exploration.

Peripapillary Vessel Density In Unilateral Preperimetric Glaucoma

Purpose

To investigate vessel density (VD) of radial peripapillary capillaries (RPC) and structural alterations in patients with unilateral preperimetric glaucoma (PPG) using optical coherence tomography angiography (OCTA).

Methods

This cross-sectional observational study included 13 untreated patients with unilateral PPG. PPG eyes had larger excavation and abnormal thinning of retinal nerve fiber layer (RNFL) and/or ganglion cell complex (GCC) compared with fellow eyes (F). Both RNFL and GCC thickness in F were statistically within normal limits and/or borderline. The RPC VD on optic disc (idVD), of peripapillary (ppVD) and whole image (wiVD) scan area was measured. Twenty healthy eyes (H) served as controls. Structural and vascular parameters obtained by spectral-domain OCT/OCTA (Optovue; Fremont, CA) were compared between PPG, F and H.

Results

Mean RNFL and GCC average thickness in microns differed significantly (p<0.001) between PPG (82.4±7.1, 81.4±5.9), F (91.0±7.1, 88.5±3.8) and H (103.5±6.0, 99.3±5.7). PPG compared with F showed significantly (p<0.001) lower mean ppVD (43.8%±3.0% versus 47.8%±3.2%) and wiVD (45.9%±3.5% versus 50.1%±3.9%). Mean ppVD (49.7%±2.4%) and wiVD (52.6%±3.0%) in H were not significantly higher than in F. Mean idVD showed no significant differences among the 3 groups. Areas under the receiver operating characteristic curves (AUROCs) for RNFL, GCC, ppVD and wiVD between PPG and H were excellent (>0.9). AUROCs between F and H demonstrated an excellent diagnostic ability for structural parameters and a poor one (<0.7) for vascular parameters.

Conclusion

Affected eyes of patients with unilateral PPG demonstrated significant RPC dropout. Clinically unaffected eyes showed thinner structural parameters but no significant microvasculature differences compared with non-glaucomatous eyes. Diagnostic ability of peripapillary vascular parameters was not superior to structural measurements. Microvascular dysfunction seems to be an early but not a primary event in glaucoma continuum at the stage of undetectable visual field loss. OCTA can be useful in early glaucoma diagnosis.

Measuring Glaucomatous Focal Perfusion Loss in the Peripapillary Retina Using OCT Angiography

PURPOSE

To measure low perfusion areas (LPAs) and focal perfusion loss (FPL) in the peripapillary retina using OCT angiography (OCTA) in glaucoma.

DESIGN

Prospective, observational study.

PARTICIPANTS

A total of 47 patients with primary open-angle glaucoma (POAG) and 36 normal participants were analyzed.

METHODS

One eye of each subject was scanned using an AngioVue (Optovue, Fremont, CA) 4.5-mm OCTA scan centered on the disc. En face nerve fiber layer (NFL) plexus angiogram was generated. With the use of custom software, a capillary density map was obtained by computing the fraction of area occupied by flow pixels after low-pass filtering by local averaging 21×21 pixels. The low-perfusion map is defined by local capillary density below 0.5 percentile over a contiguous area above 98.5 percentile of the normal reference population. The LPA parameter is the cumulative area, and the FPL is the percent capillary density loss (relative to normal mean) integrated over the LPA.

MAIN OUTCOME MEASURES

Peripapillary retinal LPA and FPL.

RESULTS

Among patients with POAG, 3 had preperimetric glaucoma and 44 had perimetric glaucoma, with visual field (VF) mean deviation (MD) of -5.14±4.25 decibels (dB). The LPA was 3.40±2.29 mm² in those with POAG and 0.11±0.18 mm² in normal subjects (P < 0.001). The FPL was 21.8%±17.0% in those with POAG and 0.3%±0.7% in normal subjects (P < 0.001). The diagnostic accuracy as measured by the area under the receiver operating curve was 0.965 for both LPA and FPL, with a sensitivity of 93.7% at 95% specificity. The repeatability as measured by intraclass correlation coefficient was 0.977 for LPA and 0.958 for FPL. The FPL had excellent correlation with VF MD (Spearman's rho = -0.843), which was significantly (P = 0.008) better than the correlation between NFL thickness and VF MD (rho = 0.760). The hemispheric difference correlation between FPL and VF (Spearman's rho = 0.770) was significantly (P < 0.001) higher than the hemispheric difference correlation between LPA and VF (rho = 0.595).

CONCLUSIONS

The low-perfusion map and LPA and FPL parameters are able to assess the location and severity of focal glaucoma damage with good agreement with VF.

Systemic Determinants of Peripapillary Vessel Density in Healthy African Americans: The African American Eye Disease Study

PURPOSE

To determine the relationship between systemic factors and radial peripapillary capillary (RPC) vessel density (VD) in healthy African American (AA) participants of the African American Eye Disease Study.

DESIGN

A population-based, cross-sectional study.

METHODS

A total of 4135 eyes from 2127 AA participants aged 40 years and older in Inglewood, California, were imaged for 6×6-mm optic disc scans on a spectral-domain optical coherence tomography angiography (OCTA) device. Of these, 1029 eyes from 1029 participants who met the inclusion and exclusion criteria were analyzed, including only 1 eye per participant. Custom software was used to quantify RPC VD. Multivariate linear regression was used to identify systemic factors associated with RPC VD with a significance level set at 0.05. The contribution of each variable to the final model was estimated with the magnitude of standardized regression coefficients (SRCs). The fit of the final model was measured by R².

RESULTS

The average RPC VD was 0.346±0.045. Controlling for signal strength, the systemic variables in the final multivariate model associated with reduced RPC VD were older age (β = -0.0123 per decade; SRC = -0.2733; P < .0001), male sex (β = -0.0067; SRC = -0.0716; P = .0060), and longer diabetes duration (β = -0.0022 per 5 years; SRC = -0.0527; P = .0427). The model R² was 0.3689.

CONCLUSIONS

Age, sex, and systemic influences, such as diabetes duration, need to be considered when assessing changes in RPC VD in glaucoma and other ocular diseases. Longitudinal studies are needed to investigate whether reduced RPC VD and the factors that affect it are associated with an increased risk of developing glaucomatous nerve damage.

Ocular Determinants of Peripapillary Vessel Density in Healthy African Americans: The African American Eye Disease Study

Purpose

The African American (AA) population has unique ocular anatomic characteristics and a disproportionately high incidence of glaucoma, which is associated with lower peripapillary vessel density (VD). This study aimed to identify ocular determinants of peripapillary VD in healthy AAs.

Methods

This was a cross-sectional, population-based study of 1029 AAs, ages 40 and older. Participants underwent examination to obtain axial length (AL), IOP, central corneal thickness (CCT), mean retinal nerve fiber layer (RNFL) thickness, visual field mean deviation (MD), and 6 × 6-mm optical coherence tomography angiography scans of the optic nerve. Participants with glaucoma, vision-threatening diabetic retinopathy, or other relevant ocular disease were excluded. Prototype software was used to quantify VD. A multivariable regression model, controlling for age and signal strength, identified the ocular variables that predicted peripapillary VD. The contribution of each variable was assessed with the magnitude of standardized regression coefficients (SRC).

Results

Based on univariate regressions, AL, RNFL thickness, and MD had significant associations with peripapillary VD (all P < 0.001). In the final multivariate model, lower mean RNFL thickness (β = 0.0022, P < 0.001, SRC = 0.542) and longer AL (β = -0.0055, P < 0.001, SRC = -0.118) were associated with lower peripapillary VD, controlling for age and signal strength, with model R2 of 0.69.

Conclusions

Thinner RNFL and longer AL were the most influential ocular determinants of lower peripapillary perfusion in healthy AA eyes. Additional research is needed to clarify whether longer AL increases risk of glaucoma by affecting capillary perfusion.