The Role of Vessel Density as Measured by Optical Coherence Tomography Angiography in the Evaluation of Pseudoexfoliative Glaucoma: A Review of the Literature

INTRODUCTION

To review the existing literature about the optical coherence tomography angiography (OCTA) findings regarding peripapillary and macular vessel density (VD) in patients with pseudoexfoliative glaucoma (PXG).

METHODS

A comprehensive search of the PubMed database was conducted to include articles up to November 1, 2021, using an appropriate search algorithm. The retrieved articles were assessed for eligibility and filtered manually to exclude duplicates, while articles and book chapters cited in the reference lists of the eligible articles obtained by this method were reviewed so as not to miss any relevant studies.

RESULTS

There is consistency among the studies published so far that a significant decrease in peripapillary VD exists in eyes with PXG compared to controls, and macular VD has also been reported to be significantly lower in PXG eyes than controls. However, the existing literature remains controversial regarding OCTA findings in eyes with PXG compared to those with primary open-angle glaucoma (POAG). Several studies have found that peripapillary VD and macular VD were significantly lower in PXG than POAG, while other studies reported no significant difference.

CONCLUSIONS

Eyes with PXG were found to present decreased peripapillary and macular VD compared to control eyes, suggesting that a vascular component, including optic nerve hypoperfusion, may be implicated in the pathogenesis of PXG.

Peripapillary and Macular Vessel Density Measurement With Optical Coherence Tomography Angiography in Exfoliation Syndrome

PRECIS

Although peripapillary retinal nerve fiber layer thickness (RNFLTs) and vessel density (VD) values were similar to healthy group, eyes with exfoliation syndrome had significantly lower superficial macular VDs and minimum ganglion cell analysis values.

PURPOSE

To compare peripapillary and macular perfused capillary densities with optical coherence tomography angiography (OCT-A) between patients with eyes having exfoliation syndrome (XFS) and normal age-matched healthy controls.

PATIENTS AND METHODS

This cross-sectional study included patients diagnosed with XFS from December 2017 to January 2020 at the Glaucoma Department. Peripapillary and parafoveal superficial VDs were obtained using OCT-A. The RNFLTs and ganglion cell analysis values were compared.

RESULTS

Thirty-nine eyes of 39 XFS patients (26 women; mean age, 69.0±8.1 y) and 39 eyes of 39 healthy patients (25 women; mean age, 68.0±8.6 y) were enrolled. There were no statistically significant differences in sex or age distribution, central corneal thickness measurements, refractive errors, or intraocular pressures between both groups (all P>0.05). There were no statistically significant differences in the peripapillary VD or peripapillary RNFLT between XFS eyes and healthy eyes (P>0.05 for all). In the macular region, most superficial VD parameters were significantly reduced in the XFS group (P=0.02 for parafoveal VD, P=0.04 for both hemifields). While the average ganglion cell and internal plexiform layer (GCL+IPL) values were similar between groups (P=0.19), the minimum GCL+IPL value was lower in the XFS group than in the healthy group (P=0.03).

CONCLUSION

Although structural test results, especially peripapillary RNFLT and mean GCL+IPL, were similar between the healthy and XFS groups, macular VD values were lower in XFS eyes. Our findings implicate microvascular damage can be the mechanism underlying XFS-related changes and indicate that it precedes significant structural damage.

Peripapillary perfused capillary density in true versus pseudoexfoliation syndrome: An OCTA study

PURPOSE

To compare peripapillary perfused capillary density (PCD) among eyes with true exfoliation syndrome (TEX), eyes with pseudoexfoliation syndrome (PEX), and healthy control eyes.

MATERIALS AND METHODS

In this observational cross-sectional study, eyes with and without TEX or PEX were assessed by optical coherence tomography angiography (OCTA) imaging. Bilateral OCTA images (4.5 × 4.5 mm2) centered at the optic nerve head were obtained using a commercial spectral domain OCTA system. Optic nerve head perfusion was quantified using the split-spectrum amplitude decorrelation angiography algorithm. Categorical and continuous variables were compared using the chi-squared test and one-way analysis of variance, respectively. The generalized estimating equation was used to adjust for confounding factors and determine inter-ocular associations.

RESULTS

We enrolled 39 eyes with TEX, 31 eyes with PEX, and 32 control eyes. There were no significant differences among the three groups regarding age, intraocular pressure, cup-to-disc ratio, blood pressure, or axial length (all p>0.05). There were significant differences in global PCD among the three groups (p = 0.01). There were significant differences in annular PCD between the TEX and PEX groups (p = 0.027).

CONCLUSIONS

While both global and annular PCDs did not differ between the TEX and control groups, greater loss of annular PCD in the PEX group than in the TEX and control groups suggests more pronounced microvascular disturbance in PEX.

SYNOPSIS/PRECIS

Greater microvascular attenuation in PEX compared with TEX and normal control measured by OCTA.

Vessel Density in Glaucoma of Different Entities as Measured with Optical Coherence Tomography Angiography

Purpose

To compare papillary and macular vessel density (VD), as measured by optical coherence tomography angiography (OCTA), in eyes with primary open-angle glaucoma (POAG), normal-tension glaucoma (NTG) and exfoliation glaucoma (XFG).

Methods

The papillary and macular VD of 40 eyes with POAG, 19 with NTG and 21 with XFG were examined using OCTA (AngioVue™). The VD was measured at two different layers of segmentation (optic nerve head: radial peripapillary capillary [RPC] and nerve head [NH]; macula: superficial [SL] and deep [DL] retinal vascular plexus) with a 4.5×4.5mm papillary and 6×6-mm macular scan. VD was calculated by an automated density measuring tool in the AngioVue™ software.

Results

There were no significant differences in the total value of the papillary, peripapillary and macular VD. A significantly higher VD could be measured for NTG compared to POAG, as well as for XFG in the inferior nasal peripapillary sector at RPC-segmentation and at the NH-level between NDG and XFG.

Conclusion

OCTA can detect a difference in VD in the nasal inferior peripapillary sector in NTG compared with POAG and XFG. These findings may help to improve the understanding of further pathophysiological mechanisms.

Nailfold capillary morphology and platelet function in patients with exfoliative glaucoma

Purpose

The purpose of the present study was to evaluate the nailfold capillary morphological features in patients with exfoliative glaucoma (XFG) and compare them with those pertaining to primary open-angle glaucoma (POAG), normal controls and subjects with exfoliation syndrome (XFS). The second purpose was to investigate all parameters related to platelet function on the hemogram, including the platelet count (PLT), the mean platelet volume (MPV), platelet distribution width (PDW), and plateletcrit (PCT) in patients with XFG. These parameters were subsequently compared with those belonging to normal controls, POAG and XFS subjects.

Methods

This case control study involved 152 consecutive patients that were examined at the Glaucoma Department of Clinic for Eye Diseases, Clinical Centre of Serbia, as the referral center for glaucoma in Serbia, between June 2016 and December 2017.

Results

Regarding capillaroscopic characteristics, statistically significant difference was found in capillary diameter and tortuosity between the XFG and POAG group (p = 0.050 and p = 0.035) and the XFG and NC group (p = 0.003 and p = 0.044), as well as in the distribution of capillary loops and avascular zones between the XFG and NC group (p = 0.014 and p = 0.004). The subjects with XFG had lower PLT values compared to POAG patients (p = 0.022).

Conclusions

In conclusion, to the best of our knowledge, this study marks the first attempt to evaluate capillary morphology as well as to investigate all parameters related to platelet function on the hemogram, in patients with newly diagnosed XFG. Our findings revealed nailfold capillary morphological vascular changes in XFG patients. The subjects with XFG had lower PLT values and a higher MPV serum parameter compared to normal controls and patients with POAG. Further research in this field should therefore aim to evaluate the consequences of the aforementioned microvascular abnormalities in patients with XFG.

Alteration of Retinal Vessel Diameter of the Patients with Pseudoexfoliation and Optical Coherence Tomography Images

Purpose: The aim of this study was to measure retinal vessel diameter using spectral domain optical coherence tomography (SD-OCT), and to compare patients with unilateral pseudoexfoliation syndrome (PEX) with controls.Materials and Methods: 40 patients with pseudoexfoliation material (40+) eyes and (40-) eyes and 32 healthy controls was included study. Observation of pseudoexfoliative material on the anterior lens capsule or pupillar margin in one or both eyes was set as the diagnostic criteria for PEX. The diameter of superior temporal vein, inferior temporal vein; superior temporal artery and inferior temporal artery were measured by SD-OCT device.Results: when PEX (+) eyes were compared with PEX (-) eyes, a significant decrease was noted in vertical diameter of the arteries, as in the superior nasal artery. In PEX (+) patients the diameter of vascular structures was significantly decreased.Conclusion: We report a relationship between PEX and retinal vessel diameter. Vascular narrowing in the contralateral eye was also seen. Thus detection of this narrowing in the non-PEX eye vessels might be important for diagnosis and prevention of early glaucoma.

Peripapillary Perfused Capillary Density in Exfoliation Syndrome and Exfoliation Glaucoma versus POAG and Healthy Controls: An OCTA Study

PURPOSE

To compare the peripapillary perfused capillary density (PCD) among eyes with exfoliation syndrome (XFS), exfoliation glaucoma (XFG), primary open-angle glaucoma (POAG), and controls.

DESIGN

Observational, cross-sectional study.

METHODS

Optical coherence tomography angiography (OCTA) images (4.5×4.5 mm) of the optic nerve head were obtained using a commercial spectral domain OCTA system (AngioVue Avanti RTVue-XR, OptoVue, Fremont, CA). Two concentric circles with 1.95-mm (inner) and 3.45-mm (outer) diameters were placed manually, producing an annulus of width 0.75 mm centered at the optic disc. PCD was calculated as the ratio of pixels associated with capillaries to the pixels in the annulus after large blood vessel removal. Continuous variables were assessed by analysis of variance and Tukey honest significant difference (HSD) test. Multiple linear regression analysis was performed to adjust for confounding factors.

RESULTS

Forty-three XFG eyes, 31 POAG eyes matched for visual field mean deviation, 33 XFS eyes, and 45 control eyes were analyzed. PCD demonstrated a progressive decrease from controls to XFS to POAG to XFG. Pairwise comparisons revealed significant differences in PCD between each pair of groups (all P<0.01) except for PCD between XFS and POAG (P = 0.08). A multivariable model adjusting for age and stage showed a more significant decrease in PCD in XFG compared with POAG (P = 0.001).

CONCLUSIONS

PCD was more significantly decreased in XFG compared with POAG eyes and in XFS compared with control eyes. OCTA provides the first quantitative evidence of the microvascular disturbance that accompanies XFS.

Comparisons of retinal vessel diameter and glaucomatous parameters between both eyes of subjects with clinically unilateral pseudoexfoliation syndrome

Purpose

Pseudoexfoliation syndrome (PEX), the most common identifiable cause of open-angle glaucoma, might affect the retinal hemodynamics. To test this, we compared retinal vessel diameter and glaucoma-related parameters between eyes with pseudoexfoliation material (PE+) and fellow unaffected (PE-) eyes of patients with clinically unilateral PEX.

Methods

The medical records of 30 consecutive Japanese subjects were reviewed retrospectively. The retinal vessel diameters were measured and expressed as the central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) using standardized software. During the chart review, we recorded glaucoma-related parameters including intraocular pressure (IOP), visual field mean deviation (MD) value, planimetrically measured vertical cup-to-disc (C/D) ratio, circumpapillary retinal nerve fiber layer thickness (cpRNFLT) and macular inner retinal thickness (mIRT) measured by spectral-domain optical coherence tomography, anterior chamber flare (ACF), corneal endothelial cell density (CECD), and number of antiglaucoma medications.

Results

Compared with PE- eyes, the CRAE, CRVE, MD, cpRNFLT and mIRT, and CECD were significantly lower in PE+ eyes; the IOP, vertical C/D ratio, number of antiglaucoma medications, and ACF were significantly higher in PE+ eyes (P<0.0001 for all comparisons). The CRAE, cpRNFLT, and MD were correlated positively with each other (ρ = 0.456–0.499, P<0.0001–0.0002) and negatively with the IOP (ρ = -0.562- —0.432, P<0.0001–0.0006). The vertical C/D ratio was correlated positively with the IOP (ρ = 0.483, P<0.0001) and negatively with the CRAE, cpRNFLT, and MD (ρ = -0.745–-0.479, P<0.0001–0.0001).

Conclusions

Deposition of PE can cause retinal vessel narrowing in arterioles and venules. The roles and mechanisms of retinal vessel narrowing in glaucoma pathogenesis need clarification.