Microvascular Compromise Develops Following Nerve Fiber Layer Damage in Normal-Tension Glaucoma Without Choroidal Vasculature Involvement

Factors Contributing to the Development of Choroidal Microvasculature Dropout in Glaucoma Suspects and Patients with Glaucoma

We aimed to characterize and compare the occurrence of peripapillary microvasculature dropout (MvD) between glaucoma suspects and patients with glaucoma. In addition, the factors related to the development of parapapillary MvD in glaucoma suspects and patients with glaucoma were investigated. Of a total 150 eyes, 68 eyes of glaucoma suspects and 82 eyes of glaucoma patients were analyzed in this study. Univariate and multivariate logistic regression analyses were used to identify factors associated with MvD development. The classification of glaucoma patients or glaucoma suspects was not significantly associated with MvD development (beta 1.368, 95% CI, 0.718-2.608, p = 0.341). In the regression analysis of the glaucoma suspect group, greater axial length (beta 1.520, 95% CI, 1.008-2.291, p = 0.046) and baseline cup volume (beta 3.993, 95% CI, 1.292-12.345, p = 0.035) among the baseline factors and the slope of ganglion cell-inner plexiform layer (GCIPL) thickness (beta 0.027, 95% CI, 0.072-0.851, p = 0.027) and central visual field (VF) progression (beta 7.040, 95% CI, 1.781-16.306, p = 0.014) among follow-up factors were significantly associated with MvD development. In the glaucoma group, central VF progression (beta 5.985, 95% CI, 1.474-24.083, p = 0.012) and ONH depression (beta 3.765, 95% CI, 1.301-10.895, p = 0.014) among follow-up elements were observed as significant factors and the baseline factor had little relationship. MvD appears not only as a result of the progression of axonal loss of RGC in glaucoma but may also be developed due to structural changes and mechanical susceptibility of the ONH associated with baseline characteristics. Analyzing the structural susceptibility of the ONH can predict the occurrence of MvD, which can be helpful in predicting the progression of glaucoma.

Choroidal Microvasculature Dropout in Glaucoma

Glaucoma is a group of diseases characterized by distinctive visual field defect and optic nerve atrophy usually associated with elevated intraocular pressure (IOP). It is one of the most serious visual disorders and the leading cause of irreversible blindness worldwide. As a multifactorial disease, the pathogenesis of glaucoma is complicated and has been far from fully understood, where vascular factors are recognized to play an important role in its development and progression of glaucoma. Empirical researches have shown that parapapillary choroidal microvasculature dropout (CMvD) is closely associated with the impairment of optic nerve head (ONH) perfusion, probably accelerating the progression of glaucoma. Accordingly, it is necessary to explore the details regarding the relationship between CMvD and glaucoma progress, hoping to enhance the understanding of pathogenesis of glaucoma. In this review, we aimed to establish comprehensive understanding of the relationship between CMvD and glaucoma with generally going through relevant up-to-date literatures. Among the events that are closely associated with CMvD, we summarized the ones specifically involved in the term of glaucomatous pathological process, including thickness of retinal nerve fiber layer (RNFL) thickness, lamina cribrosa (LC) morphology, cricumpapillary vessel density (cpVD) and visual function such as visual field (VF) defect as well as the prognosis of glaucoma. Although researchers have made great advances, there are still many issues need to be addressed particularly concerning the pathogenic role of CMvD in glaucoma development and its clinical implications with respect to glaucoma prognosis.

Factors associated with choroidal microvascular dropout change

BACKGROUND/AIMS

To investigate the factors associated with choroidal microvasculature drop-out (MvD) enlargement detected by optical coherence tomography angiography (OCT-A) in glaucomatous eyes.

METHODS

Ninety-one eyes of 68 primary open-angle glaucoma patients were enrolled. Only eyes with a minimum of four good quality OCT-A and OCT scans of the optic nerve head acquired at least and with a minimum of 2 years follow-up were included. Area and angular circumference of MvD were analysed on en face images. Univariable and multivariable mixed effects models were constructed to identify the factors contributing to MvD area and angular circumference change over time.

RESULTS

Peripapillary MvD was detected in 53 (58.2%) eyes at baseline and in an additional 17 (18.6%) eyes during follow-up, whereas MvD was not detected in 21 (23.0 %) eyes during the entire follow-up period. In multivariable analysis, worse baseline visual field (VF) mean deviation (MD) (ß=0.27, 95% CI 0.10 to 0.44, p=0.002), greater intraocular pressure (IOP) fluctuations (ß=0.86, 95% CI 0.24 to 1.48, p=0.007), higher peak IOP (ß=0.17, 95% CI -0.01 to 0.35, p=0.067) and greater number of IOP lowering medications (ß=1.36, 95% CI 0.67 to 2.05, p<0.001) were associated with faster MvD area enlargement. Worse baseline VF MD and greater IOP fluctuation were also associated with significantly faster MvD circumferential enlargement in multivariable models.

CONCLUSION

Greater IOP fluctuation, higher peak IOP, worse baseline VF MD and greater number of glaucoma medications were significantly associated with MvD enlargement in glaucomatous eyes. The identification of factors associated with MvD enlargement may improve our understanding of the role of choroidal vasculature in glaucoma.

Peripapillary Vascular Density in Compressive Optic Neuropathy and Normal-Tension Glaucoma: A Severity-Controlled Comparison

Purpose

To investigate the differences in peripapillary vessel density (VD) between compressive optic neuropathy (CON) and normal-tension glaucoma (NTG).

Methods

We compared patients with chronic CON and NTG, particularly after strictly controlling the mean extent of macular damage by the area of the ganglion cell-inner plexiform layer (GCIPL) loss in optical coherence tomography (OCT). We compared retinal nerve fiber layer (RNFL) and GCIPL thickness from OCT and peripapillary and macular VD from OCT angiography (OCTA) between the CON and NTG groups.

Results

From the initial 184 patients with CON and 443 patients with OAG, we included 41 patients with CON (57 eyes) and 64 patients with NTG (75 eyes) with a comparable extent of macular GCIPL thinning. Under similar mean macular involvement, the peripapillary VD was significantly lower in the CON group than in the NTG group after considering the effects of age, spherical equivalent, visual field sensitivity, peripapillary RNFL (pRNFL) thickness, GCIPL thickness, and image quality scores (P < 0.001). Marked loss of VD in the temporal and nasal sectors in CON was notable, attributing to the significantly lower peripapillary VD compared to NTG.

Conclusions

Patients with CON had a significantly lower peripapillary VD than those with NTG under similar mean degrees of pRNFL thickness and GCIPL damage. Our results reveal the potential utility of OCTA VD besides OCT pRNFL thickness, in relation to different topographic patterns of pRNFL loss, and possible differences in the pathogenesis of microvascular compromise between CON and NTG.

Border tissue morphology is associated with the pattern of visual field progression in open-angle glaucoma

The etiology of open-angle glaucoma (OAG) is yet unclear. This study investigated possible risk factors, such as the morphology of the border tissue that affect the pattern of visual field (VF) progression in eyes with OAG. 166 eyes of 166 OAG patients with an externally oblique border tissue (EOBT) at least in one direction were included. EOBT was obtained by analyzing enhanced depth imaging spectral-domain optical coherence tomography images. A pointwise linear regression was used to determine VF progression by measuring the deterioration rate of each point in the VF. The odds ratio of VF progression for each risk factor was estimated using logistic regression analysis. Seventy (42.2%) eyes showed VF deterioration. In multivariate analysis, longer follow-up period, higher baseline intraocular pressure (IOP), lower mean ocular perfusion pressure (MOPP), and smaller angular location of the longest EOBT were associated with VF progression (all p values were below 0.05). In the multivariate analysis, the location of the longest EOBT was significantly associated with inferior (p = 0.002) and central (p = 0.017) VF progression. In conclusion, VF progression pattern in OAG eyes is associated with the location of the longest EOBT as well as other known risk factors.

Parapapillary Choroidal Microvasculature Dropout in Branched Retinal Vein Occlusion and Glaucoma

Purpose

To investigate parapapillary choroidal microvasculature dropout (MvD) in branch retinal vein occlusion (BRVO) patients and compare them with open-angle glaucoma (OAG) patients using optical coherence tomography angiography (OCT-A).

Methods

In total, 85 eyes of BRVO patients and 85 eyes of OAG patients, matched by age, spherical equivalent, and baseline mean deviation (MD) of the visual field (VF), were assessed. MvD was defined as complete loss of microvasculature within the choroidal layer on OCT-A. Linear regression analysis was used to obtain the slope of the MD change of the VF.

Results

The presence of MvD on OCT-A was significantly more frequent in OAG eyes (63.1%) compared to BRVO eyes (31.8%). BRVO eyes with MvD showed worse baseline MD of the VF than BRVO eyes without MvD (−10.19 ± 8.50 and −7.77 ± 6.46 dB, respectively; P = 0.045). The presence of MvD was the only factor significantly associated with MD change of the VF in OAG eyes. Lower baseline average RNFL thickness, greater MvD angle, and lower macular superficial vessel density were significantly associated with MD change of the VF in BRVO eyes.

Conclusions

OCT-A of the parapapillary area showed choroidal microvasculature impairment in both BRVO and OAG patients. However, the frequency was higher in glaucoma patients with similar degrees of VF damage, which suggests that the glaucomatous process contributes to MvD development. The effect of MvD on VF change was different between BRVO and OAG, suggesting that the underlying pathogenesis may also be different.

Quantification of localised vascular wedge-shaped defects in glaucoma

BACKGROUND

Vascular dysfunction plays a considerable role in glaucoma pathogenesis. Previous glaucoma case studies described localised wedge-shaped vascular defects, similar to retinal nerve fibre layer (RNFL) wedge defects. This study investigates the prevalence and quantification of this vessel loss, in relation to primary open angle glaucoma (POAG) parameters.

METHODS

This study included 608 eyes (351 participants): 192 PROGRESSA study participants (342 eyes) with suspect, preperimetric or early manifest POAG, observed for vascular wedge defect presence (cohort one); an additional 114 individuals (cohort two-208 eyes) with POAG at various stages of progression for wedge characterisation; and 38 controls (56 eyes). Vascular wedge defects were observed using optical coherence tomography angiography (OCTA). Wedge parameters and vessel densities were quantified using ImageJ software. RNFL and ganglion cell layer inner plexiform layer (GCLIPL) from OCT scans, and mean deviation (Humphrey visual field 24-2) were also assessed.

RESULTS

Vascular wedge defects were found in 45/342 eyes (13.2%) in cohort one, in 41/208 eyes (19.7%) in cohort two and were not found in controls. Wedge defects were mostly inferotemporal (80%), and present at all disease stages. They were associated with visual field loss in the opposite hemisphere, thinner RNFL (p < 0.001), thinner GCLIPL (p = 0.003), and focal RNFL loss corresponding with the vascular defect region.

CONCLUSION

Vascular wedge defects are present at all POAG stages even before functional change and are strongly concordant with focal RNFL loss. Further research is needed to explore these defects in particular their temporal relationship with clinical measures of POAG.

A review on albumin as a biomaterial for ocular drug delivery

Development of ocular drug delivery system is one of the most technically challenging tasks, when compared with other routes of drug delivery. Eye (an intricate organ) is highly sophisticated and sensitive organ due to presence of various structurally differed anatomical layers, which many times limits the drug delivery approaches. Despite several limitations, many advancements have been made as evidence from various recent studies involving improvement of both residence time and permeation of the drug at the ocular region. In the last few decades, albumin(s) based ophthalmic products have been gained most attention to solve the major challenges associated with conventional ocular drug delivery systems. Interestingly, an albumin-based micro, nano, conjugates, and genetically fused target specific to ligand(s) formulation being exploited through many studies for successful ocular delivery of bioactives (mostly repurposed drugs). Past and current studies suggested that albumin(s) based ocular drug delivery system is multifunctional in nature and capable of extending both drug residence time and sustaining the release of drugs to deliver desired pharmacological outcomes. Despite wide applications, still complete progress made in albumin based ocular drug delivery is limited in literature and missing in market. So, herein we presented an overview to explore the key concepts of albumin-based nanocarrier(s) including strategies involved in the treatment of ocular disease, that have yet to be explored.

Investigation of the Peripapillary Choriocapillaris in Normal Tension Glaucoma, Primary Open-angle Glaucoma, and Control Eyes

PRECIS

The peripapillary choriocapillaris (CC) was observed to be significantly impaired in normal tension glaucoma (NTG) subjects compared with normal controls using optical coherence tomography angiography (OCTA).

PURPOSE

The aim was to quantitatively evaluate the peripapillary CC in NTG, primary open-angle glaucoma (POAG), and control eyes using OCTA.

MATERIALS AND METHODS

Ninety eyes (30 controls, 30 NTG, and 30 POAG) from 73 patients were imaged using the Zeiss Plex Elite 9000. Five repeat 3×3 mm OCTA scans were acquired both nasally and temporally to the optic disc and subsequently averaged. Four CC flow deficit (FD) measures were calculated using the fuzzy C-means approach: FD density (FDD), mean FD size (MFDS), FD number (FDN), and FD area (FDA).

RESULTS

Temporal NTG CC parameters were associated with visual field index and mean deviation (P<0.05). The control group showed a significantly lower nasal FDD (nasal: 3.79±1.26%, temporal: 4.48±1.73%, P=0.03), FDN (nasal: 156.43±38.44, temporal: 178.40±45.68, P=0.02), and FDA (nasal: 0.22±0.08, temporal: 0.26±0.10, P=0.03) when compared with temporal optic disc. The NTG group showed a significantly higher FDD (NTG: 5.04±2.38%, control: 3.79±1.26%, P=0.03), FDN (NTG: 185.90±56.66, control: 156.43±38.44, P=0.04), and FDA (NTG: 0.30±0.14 mm2, control: 0.22±0.08 mm2, P=0.03) nasal to the optic disc compared with controls.

CONCLUSIONS

Association between CC parameters and glaucoma severity in NTG, but not POAG subjects, suggests vascular abnormalities may be a potential factor in the multifactorial process of glaucoma damage in NTG patients.

[Optical coherence tomography angiography (OCT-A) : Overview of the technique and the possible clinical and scientific applications]

Optical coherence tomography angiography (OCT-A) is a very promising noninvasive imaging modality. For the first time it enables a precise 3‑dimensional depiction of the retinal microcirculation without the use of contrast medium and can be carried out rapidly and simply. This makes OCT‑A interesting for both scientific and clinical applications. In many ophthalmological diseases, such as glaucoma and diabetic retinopathy, OCT‑A can detect vascular alterations even in the early stages of the disease. These alterations partially correlate with functional parameters. The use of OCT‑A in the clinical routine is currently still limited due to imaging artifacts, high acquisition costs and large amounts of data; however, the scientific interest in this new technology is enormous and from our point of view it will become established in the clinical routine in the future.

Comparison of Peripapillary Choroidal Microvasculature Dropout in Primary Open-angle, Primary Angle-closure, and Pseudoexfoliation Glaucoma

PRECIS

The prevalence of choroidal microvascular dropout (CMvD) was significantly higher in primary open-angle glaucoma (POAG) than primary angle-closure glaucoma (PACG) or pseudoexfoliation glaucoma (PXG) in the early stage. However, in the advanced stage, it did not differ among the 3 groups.

PURPOSE

The purpose of this study was to compare the prevalence of peripapillary CMvD in POAG, PACG, and PXG.

MATERIALS AND METHODS

The presence of peripapillary CMvD was identified using optical coherence tomography angiography (AngioVue/RTVue-XR) imaging of the choroid in 186 eyes from 186 subjects [age and visual field (VF) mean deviation (MD) matched; 62 POAG, 62 PACG, and 62 PXG eyes]. Prevalence of CMvD was compared among glaucoma types in early and moderate to advanced disease, as divided by VF MD (-6 dB). The association between glaucoma type and presence of CMvD was evaluated using logistic regression analysis.

RESULTS

Prevalence of CMvD was significantly different between glaucoma types in early-stage disease (PACG 7.5%, PXG 25%, and POAG 46.3%, P<0.001), but it did not differ between glaucoma types in eyes with moderate to advanced disease (PACG 59.1%, PXG 68.2%, and POAG 81%; P=0.331). After adjusting for age, sex, the β-zone peripapillary atrophy/disc ratio, and glaucoma severity (VF MD), the CMvD odds ratio was 7.50 times greater in POAG than in PACG (P=0.001).

CONCLUSIONS

CMvD was more common in POAG relative to both PACG and PXG, especially in early-stage disease. This finding suggested a role for ischemic injury in the pathogenesis of POAG.

OCTA Multilayer and Multisector Peripapillary Microvascular Modeling for Diagnosing and Staging of Glaucoma

Purpose

To develop and assess an automatic procedure for classifying and staging glaucomatous vascular damage based on optical coherence tomography angiography (OCTA) imaging.

Methods

OCTA scans (Zeiss Cirrus 5000 HD-OCT) from a random eye of 39 healthy subjects and 82 glaucoma patients were used to develop a new classification algorithm based on multilayer and multisector information. The averaged circumpapillary retinal nerve fiber layer (RNFL) thickness was also collected. Three models, support vector machine (SVM), random forest (RF), and gradient boosting (xGB), were developed and optimized for classifying between healthy and glaucoma patients, primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG), and glaucoma severity groups.

Results

All the models, the SVM (area under the receiver operating characteristic [AUROC] 0.89 ± 0.06), the RF (AUROC 0.86 ± 0.06), and the xGB (AUROC 0.85 ± 0.07), with 26, 22, and 29 vascular features obtained after feature selection, respectively, presented a similar performance to the RNFL thickness (AUROC 0.85± 0.06) in classifying healthy and glaucoma patients. The superficial vascular plexus was the most informative layer with the infero temporal sector as the most discriminative region of interest. No significant differentiation was obtained in discriminating the POAG from the NTG group. The xGB model, after feature selection, presented the best performance in classifying the severity groups (AUROC 0.76± 0.06), outperforming the RNFL (AUROC 0.67± 0.06).

Conclusions

OCTA multilayer and multisector information has similar performance to RNFL for glaucoma diagnosis, but it has an added value for glaucoma severity classification, showing promising results for staging glaucoma progression.

Translational Relevance

OCTA, in its current stage, has the potential to be used in clinical practice as a complementary imaging technique in glaucoma management.

Global assessment of arteriolar, venular and capillary changes in normal tension glaucoma

Microcirculatory insufficiency has been hypothesized in glaucoma pathogenesis. There is a scarcity of data to comprehensively examine the changes in retinal microvasculature and its role in normal tension glaucoma (NTG). We conducted a cross-sectional case-control study and included 168 eyes from 100 NTG patients and 68 healthy subjects. Quantitative retinal arteriolar and venular metrics were measured from retinal photographs using a computer-assisted program. Radial peripapillary capillary network was imaged with OCT-A and quantitative capillary metrics (circumpapillary vessel density (cpVD) and circumpapillary fractal dimension (cpFD)) were measured with a customized MATLAB program. We found that NTG was associated with decreased arteriolar and venular tortuosity, arteriolar branching angle, cpVD and cpFD. Decreased venular caliber, arteriolar and venular branching angles, cpVD and cpFD were associated with thinner average RNFL thickness. Decreased arteriolar and venular branching angles, cpVD and cpFD were also associated with worse standard automated perimetry measurements (mean deviation and visual field index). Compared with retinal arteriolar and venular metrics, regression models based on OCT-A capillary metrics consistently showed stronger associations with NTG and structural and functional measurements in NTG. We concluded that NTG eyes showed generalized microvascular attenuations, in which OCT-A capillary metrics attenuations were more prominent and strongly associated with NTG.

Combined Multi-Modal Assessment of Glaucomatous Damage With Electroretinography and Optical Coherence Tomography/Angiography

Purpose

To compare the diagnostic performance and to evaluate the interrelationship of electroretinographical and structural and vascular measures in glaucoma.

Methods

For 14 eyes of 14 healthy controls and 15 eyes of 12 patients with glaucoma ranging from preperimetric to advanced stages optical coherence tomography (OCT), OCT-angiography (OCT-A), and electrophysiological measures (multifocal photopic negative response ratio [mfPhNR] and steady-state pattern electroretinography [ssPERG]) were applied to assess changes in retinal structure, microvasculature, and function, respectively. The diagnostic performance was assessed via area-under-curve (AUC) measures obtained from receiver operating characteristics analyses. The interrelation of the different measures was assessed with correlation analyses.

Results

The mfPhNR, ssPERG amplitude, parafoveal (pfVD) and peripapillary vessel density (pVD), macular ganglion cell inner plexiform layer thickness (mGCIPL) and peripapillary retinal nerve fiber layer thickness (pRNFL) were significantly reduced in glaucoma. The AUC for mfPhNR was highest among diagnostic modalities (AUC: 0.88, 95% confidence interval: 0.75-1.0, P < 0.001), albeit not statistically different from that for macular (mGCIPL: 0.76, 0.58-0.94, P < 0.05; pfVD: 0.81, 0.65-0.97, P < 0.01) or peripapillary imaging (pRNFL: 0.85, 0.70-1.0, P < 0.01; pVD: 0.82, 0.68-0.97, P < 0.01). Combined functional/vascular measures yielded the highest AUC (mfPhNR-pfVD: 0.94, 0.85-1.0, P < 0.001). The functional/structural measure correlation (mfPhNR-mGCIPL correlation coefficient [rs]: 0.58, P = 0.001; mfPhNR-pRNFL rs: 0.66, P < 0.001) was stronger than the functional-vascular correlation (mfPhNR-pfVD rs: 0.29, P = 0.13; mfPhNR-pVD rs: 0.54, P = 0.003).

Conclusions

The combination of ERG measures and OCT-A improved diagnostic performance and enhanced understanding of pathophysiology in glaucoma.

Translational Relevance

Multimodal assessment of glaucoma damage improves diagnostics and monitoring of disease progression.

Peripapillary vessel parameters and mean ocular perfusion pressure in young healthy eyes: OCT angiography study

BACKGROUND

To investigate the relationship between estimated mean ocular perfusion pressure (MOPP) and peripapillary perfusion density (PD) or vessel density (VD) as measured by spectral-domain optical coherence tomography angiography (OCTA) in young healthy eyes.

METHODS

132 healthy participants (264 eyes) under 45 years of age underwent optic disc OCTA scan sized 3×3 mm to acquire PD and VD in the superficial vascular complex (SVC). Optic nerve head (ONH) parameters including retinal nerve fibre layer (RNFL) thickness, rim area and disc area were measured. MOPP was estimated from systemic blood pressure and intraocular pressure (IOP). A linear mixed model was used to find the systemic and ocular factors associated with PD and VD.

RESULTS

The average age of the subjects was 25.8±6.5 years. PD and VD showed a significant correlation with RNFL thickness (r=0.224, p<0.001 and r=0.214, p<0.001, respectively), but with MOPP, the correlation was only marginally significant (r=0.105, p=0.09 and r=0.112, p=0.07, respectively). After controlling for confounding factors, including age, sex, IOP, central corneal thickness, axial length and OCTA signal strength, PD and VD were significantly associated with ONH parameters (all p<0.05) but not with estimated MOPP (all p>0.05).

CONCLUSION

PD and VD in the SVC were significantly associated with ONH parameters while showing no association with estimated MOPP. OCTA-derived VD may not represent perfusion pressure, but is rather more dependent on peripapillary structure.

Deep-layer Microvasculature Dropout in Preperimetric Glaucoma Patients

PURPOSE

To compare disease severity between preperimetric primary open-angle glaucoma (POAG) patients with and without deep-layer microvasculature dropout.

MATERIALS AND METHODS

Ninety-four eyes of 94 preperimetric POAG patients with β-zone parapapillary atrophy (βPPA) were categorized according to the presence of deep-layer microvasculature dropout defined as a complete loss of microvasculature within the choroid or scleral flange on optical coherence tomography angiography. Parameters representing disease severity, that is, visual field (VF) mean deviation (MD), global and sectoral (6-sector) retinal nerve fiber layer (RNFL) thickness, and other factors including age, focal lamina cribrosa (LC) defect, width of βPPA with and without Bruch membrane (BM) (βPPA+BM and βPPA-BM), and optic disc hemorrhage were compared between eyes with and without dropout.

RESULTS

Deep-layer microvasculature dropout was observed in 33 preperimetric POAG eyes (35.1%). Eyes with dropout had significantly thinner RNFL in all areas except the inferonasal sector, worse VF MD, and higher prevalence of focal LC defect, and larger βPPA-BM (P<0.05), whereas the 2 groups did not differ in age, disc hemorrhage, or βPPA+BM width (P>0.05). In the multivariable logistic regression, worse VF MD [odds ratio (OR), 1.485; P=0.045], thinner RNFL (OR, 1.141; P<0.001), and higher prevalence of focal LC defect (OR, 6.673; P<0.001) were significantly associated with dropout.

CONCLUSIONS

Deep-layer microvasculature dropout was observed in a considerable number of preperimetric POAG eyes, and worse disease severity was associated with dropout. Future studies elucidating the pathogenic role of deep-layer microvasculature dropout in the development and progression of glaucoma are warranted.

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.

Optical Coherence Tomography Angiography Compared With Optical Coherence Tomography Macular Measurements for Detection of Glaucoma

Importance

Whether optical coherence tomography angiography (OCT-A) outperforms OCT to detect glaucoma remains inconclusive.

Objective

To compare (1) the diagnostic performance for detection of glaucoma and (2) the structure-function association between inner macular vessel density and inner macular thickness.

Design, Setting, and Participants

This cross-sectional study included 115 patients with glaucoma and 35 healthy individuals for measurements of retinal thickness and retinal vessel density, segmented between the anterior boundary of internal limiting membrane and the posterior boundary of the inner plexiform layer, over the 3 × 3-mm2 macula using swept-source OCT. All participants were Chinese. Visual sensitivity corresponding to the 3 × 3-mm2 macular region was expressed in unlogged 1/lambert for investigation of the structure-function associations. Diagnostic performance was evaluated with area under the receiver operating characteristic curves (AUCs). The study was conducted between January 12, 2016, and December 12, 2016.

Main Outcomes and Measures

Area under the receiver operating characteristic curve and R2 analysis.

Results

Of the 115 patients with glaucoma, 42 (36.5%) were women (mean [SD] age, 53.5 [13.4] years); of the 35 individuals with healthy eyes, 25 (71.4%) were women (age, 60.6 [5.9] years). Inner macular vessel density and thickness were 4.3% (95% CI, 2.4%-6.1%) and 21.1 μm (95% CI, 17.4-24.9 μm) smaller, respectively, in eyes with glaucoma compared with healthy eyes. The AUC of mean inner macular thickness for glaucoma detection was greater than that of mean inner macular vessel density (difference, 0.17; 95% CI, 0.01-0.31; P = .03). At 90% specificity, the sensitivity of mean inner macular thicknesses for detection of glaucoma was greater than that of mean inner macular vessel densities (difference, 29.2%; 95% CI, 11.5%-64.6%; P = .02). The strength of the structure-function association was stronger for mean inner macular thickness than mean inner macular vessel density in the linear (difference in R2 = 0.38; 95% CI, 0.22-0.54; P < .001) and nonlinear (difference in R2 = 0.36; 95% CI, 0.21-0.51; P < .001) regression models.

Conclusions and Relevance

In this study, OCT measurement of inner macular thickness shows a higher diagnostic performance to detect glaucoma and a stronger structure-function association than the currently used OCT-A measurement of inner macular vessel density. These findings may suggest that OCT-A of the macula has a limited role in the diagnostic evaluation of glaucoma.

Comparison of vascular-function and structure-function correlations in glaucomatous eyes with high myopia

BACKGROUND/AIMS

To determine the usefulness of peripapillary retinal vessel density (VD) measured using optical coherence tomography (OCT) angiography (OCTA) in the evaluation of glaucomatous visual field damage in highly myopic eyes with primary open-angle glaucoma (POAG).

METHODS

This cross-sectional observational study enrolled a total of 124 myopic POAG eyes consisting of 40 eyes showing a segmentation error (SE) in OCT scans and 84 eyes without an SE. The peripapillary retinal VD, circumpapillary retinal nerve fibre layer thickness (RNFLT) and visual field sensitivity loss (VFSL) were assessed using OCTA, spectral-domain OCT and standard automated perimetry, respectively. The topographical correlations between the VD and VFSL, and between the RNFLT and VFSL were determined in subgroups divided according to the presence of an SE.

RESULTS

The peripapillary retinal VD showed significant topographical correlation with VFSL both in the highly myopic POAG eyes without an SE globally (R=0.527, p<0.001), and in temporal (R=0.593), temporal-superior (R=0.543), nasal-inferior (R=0.422) and temporal-inferior sectors (R=0.600, all p<0.001), and in those with an SE globally (R=0.343, p=0.030), and in temporal (R=0.494, p=0.001), temporal-superior (R=0.598, p<0.001), and temporal-inferior sectors (R=0.424, p=0.006). The correlation with VFSL did not differ between the VD and RNFLT in the eyes without an SE CONCLUSION: Peripapillary VD as measured with OCTA showed a topographical correlation with VFSL in highly myopic POAG eyes regardless of the presence of an OCT SE OCTA may be a useful adjunct for evaluating glaucomatous visual field damage in high myopia, where the OCT results are frequently confounding.

[Optical coherence tomography angiography: Value for glaucoma diagnostics]

BACKGROUND

Optical coherence tomography angiography (OCTA) is a novel noninvasive method which enables a quantitative evaluation of retinal and optic nerve head (ONH) perfusion. In this article, we discuss the principles of the application of OCTA and give a summary of the knowledge gained by using this method in glaucoma patients.

METHODS

This article is based on a selective literature search and the analysis of own data.

RESULTS

Quantitative OCTA parameters have a good reproducibility in glaucoma patients. Glaucoma patients show a reduced flow density (FD) in the ONH and in the area of the macula compared with a healthy control group. The FD parameters show a good diagnostic discriminatory power but are not superior to the structural parameters used in routine diagnostics. The reduced FD measured using OCTA correlates with the extent of functional and structural glaucoma damage.

CONCLUSION

The OCTA is noninvasive, fast and reproducible. Initial results from studies on glaucoma patients show the high diagnostic potential of this method. The OCTA could become a part of clinical glaucoma management in the future.

Optical Coherence Tomography Angiography in Glaucoma: A Review

BACKGROUND

Glaucoma is the leading cause of irreversible blindness worldwide. Several techniques exist for the diagnosis and follow-up of patients. Optical coherence tomography (OCT) angiography (OCTA) is a recently developed technique that provides a quantitative assessment of the microcirculation of the retina and choroid in a fast, noninvasive way. Despite it being a novel technique, several publications have already been done in the glaucoma field. However, a summary of findings is currently lacking.

AIMS

To perform a literature review to assess the role of OCTA in glaucoma diagnosis and follow-up.

METHODS

A database search was carried out using MEDLINE, Embase, and Web of Science, including all original works registered until July 23, 2017.

RESULTS

OCTA (1) has a high repeatability and reproducibility, (2) has good discriminatory power to differentiate normal eyes from glaucoma eyes, (3) is more strongly correlated with visual function than conventional OCT, (4) has good discriminatory power to differentiate early-glaucoma eyes from normal eyes (i.e., at least equal to that of OCT), (5) reaches a floor effect at a more advanced disease stage than OCT, and (6) is able to detect progression in glaucoma eyes.

CONCLUSION

OCTA shows potential to become a part of everyday glaucoma management.

Comparison of peripapillary vessel density between preperimetric and perimetric glaucoma evaluated by OCT-angiography

Purpose

To determine peripapillary vessel density in eyes with perimetric glaucoma (PG) or preperimetric glaucoma (PPG) compared to normal controls using optical coherence tomography-angiography (OCT-A).

Methods

We recruited 13 patients with unilateral perimetric normal-tension glaucoma (NTG) and fellow preperimetric NTG showing only inferotemporal retinal nerve fiber layer (RNFL) defect in red-free RNFL photography in both eyes. We also enrolled 9 healthy controls. Using OCT-A, radial peripapillary capillary densities at inferotemporal and superotemporal regions were evaluated. Paired comparison of peripapillary vessel density was performed for PG eye, PPG eye, and normal eye.

Results

A total of 26 eyes of the 13 patients with unilateral PG and fellow PPG eyes and 18 eyes of 9 normal controls were analyzed. Vessel densities at the whole peripapillary region and inferotemporal region in PG eyes were significantly lower than those in PPG eyes (P = 0.001, P<0.001, respectively). Comparison between PPG and normal eyes showed no significant difference in the whole peripapillary region or the inferotemporal region (P = 0.654, P = 0.174, respectively). There was no significant (P = 0.288) difference in vessel density at superotemporal region among the three types of eyes (PG eye, PPG eye, and normal eye).

Conclusion

PPG eyes and normal eyes were found to have the similar densities of peripapillary microvasculature at the area with nerve fiber layer defect, whereas in PG eye, there was a significant decrease in vessel density at the area of RNFL thinning. This provides evidence that microvascular compromise in the retina might be a secondary change to nerve fiber layer degeneration in the pathogenesis of NTG.

Optical Coherence Tomography Angiography: A New Tool in Glaucoma Diagnostics and Research

Optical coherence tomography angiography (OCTA) is a new modality in ocular imaging which provides high resolution view of the vascular structures in the retina and optic nerve head. This technology has the advantages of being noninvasive, rapid and reproducible. OCTA is becoming a valuable tool for evaluating many retinal and optic nerve diseases. This article provides a brief introduction to the technology and its application in the field of glaucoma diagnostics.