Reproducibility of Optical Coherence Tomography Angiography Macular and Optic Nerve Head Vascular Density in Glaucoma and Healthy Eyes

Diagnostic performance of optical coherence tomography angiography in glaucoma: a systematic review and meta-analysis

BACKGROUND

Compared with current imaging methods, the diagnostic performance and the advantages and limitations of optical coherence tomography angiography (OCTA) remain unclear. We performed a systematic review and meta-analysis of studies investigating vessel density (VD) in patients with glaucoma using OCTA.

METHODS

We conducted a literature search on PubMed, Scopus, Web of Science, ISI Conference Proceedings and Google Scholar, along with a manual search, from January 2006 to March 2018. We included prospective studies that used OCTA to compare the VD in glaucomatous eyes with healthy control eyes.

RESULTS

Of 3045 screened articles, 24 were included in a broad characterisation and 18 in the meta-analysis. We observed a statistically significant reduction in the mean peripapillary VD (MPVD) in glaucoma (MPVD: 57.53%, 95% CI 52.60 to 62.46, p< 0.001) compared with controls (MPVD: 65.47%, 95% CI 59.82 to 71.11; standardised mean difference [SMD], -1.41, 95% CI -1.62 to -1.20, p< 0.001) for 888 glaucomatous and 475 healthy eyes, and also in the mean-whole optic nerve image VD (SMD, -9.63, 95% CI -10.22 to -9.03, p<0.001), mean inside-disc VD (SMD, - 9.51, 95% CI -12.66 to -6.36, p<0.05) and mean parafoveal VD (SMD, -3.92, 95% CI -4.73 to -3.12, p<0.001). Subgroup analyses revealed a significant difference in the MPVD across glaucoma subtypes and OCTA devices.

CONCLUSION

This suggests the diagnostic utility of OCTA in detecting glaucomatous eyes; however, further longitudinal prospective studies are welcomed to characterise vascular changes in glaucoma.

Reproducibility of Macular Vessel Density Calculations Via Imaging With Two Different Swept-Source Optical Coherence Tomography Angiography Systems

Purpose

To evaluate the reproducibility of vessel density calculations using different binarization methods obtained via two commercially available swept-source optical coherence tomography angiography (SS-OCTA) systems.

Methods

Healthy volunteers were imaged using two swept-source optical coherence tomography angiography (SS-OCTA) devices, PLEXElite and Triton. SS-OCTA examinations were performed using a 3 × 3-mm volume scan pattern centered on the fovea. A total of six methods were used for binarization in ImageJ, two global thresholding and four local adaptive thresholding methods. Resultant vessel density values were compared between the instruments and binarization methods. Images for 60 eyes from 30 healthy subjects were assessed by two reviewers who were blinded to the scanning system used.

Results

Twenty-two eyes were excluded due to poor image quality (17 eyes from Triton, 4 eyes from PLEXElite, and 1 eye from both instruments, P = 0.003). A final 38 eyes from 23 subjects were eligible for analysis. Each binarization method and instrument led to different median values. The coefficients of variation for vessel density measurements ranged from 0.3% to 2.3% and 0.6% to 4.7% for the PLEXElite and Triton, respectively. Local adaptive thresholding methods revealed higher reproducibility than did global thresholding methods for both devices.

Conclusions

Macular scans with both SS-OCTA instruments showed good reproducibility for vessel density measurements. PLEXElite recorded fewer poor images and had higher reproducibility than did Triton. These findings will inform the selection of proper binarization methods for the clinical detection of vascular diseases affecting the central retina.

Translational Relevance

The reproducibility for macular vessel measurements with SS-OCTA instruments was good. PLEXElite recorded fewer poor images and had higher reproducibility than did Triton.

Diagnostic Performance of Macular Versus Peripapillary Vessel Parameters by Optical Coherence Tomography Angiography for Glaucoma

PURPOSE

To compare the diagnostic ability of the vessel parameters in macular and peripapillary regions measured using spectral-domain optical coherence tomography angiography (SD-OCTA) in differentiating primary open-angle glaucoma (POAG) from healthy eyes.

METHODS

POAG patients and healthy subjects underwent 6 × 6-mm scans centered on the macula and optic nerve head. Commercially available automatic segmentation created en face images from SD-OCTA of the superficial retinal layer (SRL) of the macular (m) and peripapillary (cp) regions. Vessel area density (VAD), vessel skeleton density (VSD), vessel complexity index (VCI), and flux were calculated. Area under curve (AUC) statistics controlled for age and intereye correlation.

RESULTS

Of 126 eyes from 79 patients who underwent SD-OCTA macula and peripapillary imaging, 50 eyes from 35 POAG patients and 37 healthy eyes from 25 control subjects had good quality imaging and were studied. Diagnostic accuracies of four perfusion parameters, VAD, VSD, VCI, and flux, were significantly greater in the peripapillary compared with the macular regions. For VAD, the cpAUC was 0.84 and mAUC was 0.73 (AUC difference: P = 0.026). For VSD, the cpAUC was 0.84 and mAUC was 0.72 (ΔP = 0.015). For VCI, the cpAUC was 0.80 and mAUC was 0.70 (ΔP = 0.045). For flux, the cpAUC = 0.87 and mAUC was 0.76 (ΔP = 0.0091).

CONCLUSIONS

Peripapillary perfusion parameters performed better than macular perfusion parameters for glaucoma diagnosis, supporting the idea that glaucomatous superficial retinal vascular changes are more pronounced in the peripapillary region.

TRANSLATIONAL RELEVANCE

The diagnostic accuracy of OCTA perfusion parameters of the superficial retinal microcirculation was greater for the peripapillary region than the macular region in the diagnosis of glaucoma.

Comparison of methods to quantify macular and peripapillary vessel density in optical coherence tomography angiography

Purpose

To compare macular and peripapillary vessel density values calculated on optical coherence tomography angiography (OCT-A) images with different algorithms, elaborate conversion formula, and compare the ability to discriminate healthy from affected eyes.

Methods

Cross-sectional study of healthy subjects, patients with diabetic retinopathy, and glaucoma patients (44 eyes in each group). Vessel density in the macular superficial capillary plexus (SCP), deep capillary plexus (DCP), and the peripapillary radial capillary plexus (RCP) were calculated with seven previously published algorithms. Systemic differences, diagnostic properties, reliability, and agreement of the methods were investigated.

Results

Healthy eyes exhibited higher vessel density values in all plexuses compared to diseased eyes regardless of the algorithm used (p<0.01). The estimated vessel densities were significantly different at all the plexuses (p<0.0001) as a function of method used. Inter-method reliability and agreement was mostly poor to moderate. A conversion formula was available for every method, except for the conversion between multilevel and fixed at the DCP. Substantial systemic, non-constant biases were evident between many algorithms. No algorithm outperformed the others for discrimination of patients from healthy subjects in all the retinal plexuses, but the best performing algorithm varied with the selected plexus.

Conclusions

Absolute vessel density values calculated with different algorithms are not directly interchangeable. Differences between healthy and affected eyes could be appreciated with all methods with different discriminatory abilities as a function of the plexus analyzed. Longitudinal monitoring of vessel density should be performed with the same algorithm. Studies adopting vessel density as an outcome measure should not rely on external normative databases.

Optical Coherence Tomography Angiography in Glaucoma

Optical coherence tomography angiography (OCTA) comprises different OCT-based technologies developed for non-invasive assessment and measurement of optic nerve head and retinal perfusion. Currently the most clinically established approach is based on the split spectrum amplitude decorrelation algorithm, which detects moving red blood cells and eliminates all other information. The two main clinical fields in which OCTA offers clinically useful information are investigation of the macular retina (e.g. in macular degeneration and diabetic macular disease) and glaucoma. For glaucoma, the optic nerve head and the peripapillary retinal perfusion in the retinal nerve fiber layer, and the superficial perifoveal macular vasculature are the areas of interest. This review provides a comprehensive summary of the most important current and potential future applications of OCTA in glaucoma, but it does not address the nonglaucomatous optic nerve head or peripapillary and macular diseases.

Repeatability of vessel density measurements using optical coherence tomography angiography in retinal diseases

AIM

To analyse the repeatability of vessel density (VD) measurements using optical coherence tomography angiography (OCTA) in patients with retinal diseases.

METHODS

Two consecutive VD measurements using OCTA were analysed prospectively in patients with retinal diseases (diabetic macular oedema (DME), retinal vein occlusion (RVO) with macular oedema, epiretinal membrane (ERM), wet age-related macular degeneration (AMD)). The intraclass correlation coefficient (ICC), coefficient of variation (CV) and test-retest SD of VD measurements were assessed, and linear regression analyses were conducted to identify factors related to repeatability.

RESULTS

A total of 134 eyes were analysed involving 20 eyes with DME, 44 eyes with RVO with macular oedema, 50 eyes with ERM and 20 eyes with wet AMD. The mean age was 64.9 years, and the mean best-corrected visual acuity (BCVA) was 0.24. The mean central macular thickness (CMT) was 391.6 µm, and the mean ganglion cell-inner plexiform layer (GC-IPL) thickness was 61.4 µm. In all four diseases, the ICC and CV of the full VD were 0.812 and 6.72%, respectively. Univariate analyses showed that the BCVA (B, 8.553; p=0.031), signal strength (B, -1.688; p=0.050), CMT (B, 0.019; p=0.015) and mean GC-IPL thickness (B, -0.103; p=0.001) were significant factors that affected the repeatability. Multivariate analyses of these factors showed a significant result for the GC-IPL thickness.

CONCLUSIONS

Measurements of the VD using OCTA showed relatively good repeatability for various retinal diseases. The BCVA, signal strength, CMT and GC-IPL thickness affected the repeatability, so these factors should be considered when analysing the VD.

Macular and Optic Nerve Head Vessel Density and Progressive Retinal Nerve Fiber Layer Loss in Glaucoma

PURPOSE

To investigate prospectively the relationship between macular and peripapillary vessel density and progressive retinal nerve fiber layer (RNFL) loss in patients with mild to moderate primary open-angle glaucoma.

DESIGN

Prospective, observational study.

PARTICIPANTS

One hundred thirty-two eyes of 83 patients with glaucoma followed up for at least 2 years (average: 27.3±3.36 months).

METHODS

Measurements of macular whole image vessel density (m-wiVD) and optic nerve head whole image vessel density (onh-wiVD) were acquired at baseline using OCT angiography. RNFL, minimum rim width (MRW), and ganglion cell plus inner plexiform layer (GCIPL) thickness were obtained semiannually using spectral-domain OCT. Random-effects models were used to investigate the relationship between baseline vessel density parameters and rates of RNFL loss after adjusting for the following confounding factors: baseline visual field mean deviation, MRW, GCIPL thickness, central corneal thickness (CCT), and mean intraocular pressure during follow-up and disc hemorrhage, with or without including baseline RNFL.

MAIN OUTCOME MEASURES

Effects of m-wiVD and onh-wiVD on rates of RNFL loss over time.

RESULTS

Average baseline RNFL thickness was 79.5±14.8 μm, which declined with a mean slope of -1.07 μm/year (95% confidence interval, -1.28 to -0.85). In the univariate model, including only a predictive factor and time and their interaction, each 1% lower m-wiVD and onh-wiVD was associated with a 0.11-μm/year (P < 0.001) and 0.06-μm/year (P = 0.031) faster rate of RNFL decline, respectively. A similar relationship between low m-wiVD and onh-wiVD and faster rates of RNFL loss was found using different multivariate models. The association between vessel density measurements and rate of RNFL loss was weak (r² = 0.125 and r² = 0.033 for m-wiVD and onh-wiVD, respectively). Average CCT also was a predictor for faster RNFL decline in both the univariate (0.11 μm/year; P < 0.001) and multivariate models.

CONCLUSIONS

Lower baseline macular and optic nerve head (ONH) vessel density are associated with a faster rate of RNFL progression in mild to moderate glaucoma. Assessment of ONH and macular vessel density may add significant information to the evaluation of the risk of glaucoma progression and prediction of rates of disease worsening.

OCTA vessel density changes in the macular zone in glaucomatous eyes

PURPOSE

To evaluate whether macular optical coherence tomography angiography (OCTA) can detect altered vessel density (VD) in the superficial and deep vascular plexus in glaucomatous eyes and to compare the diagnostic utility of the individual VD parameters.

METHODS

The macular VD of 135 eyes, comprising 85 eyes diagnosed with glaucoma and 50 healthy control eyes, was examined using two OCTA devices (AngioPlex-Zeiss Meditec, Inc., Dublin, CA, USA, and AngioVue-OptoVue, Inc., Fremont, CA, USA). All study participants had neither vascular pathology, diabetes, nor vasoactive medication. The macular VD was measured at two different levels of segmentation (superficial [SL] and deep [DL] retinal vascular plexus) with a 6 × 6-mm macula scan, and VD was correlated with various structural and functional measurements. In order to test the accuracy of differentiation between eyes with and without glaucoma, we calculated the receiver operating characteristic (ROC) curve and the area under the curve (AUC).

RESULTS

Macular VD was significantly lower in both SL and DL in glaucomatous eyes than in healthy eyes (p = SL < 0.0001; DL = 0.009). There was no significant difference in VD between the SL and the DL (p = 6.60 · 10^-18). The greatest reduction of VD in glaucomatous eyes was found in the inferior macular sector. There was no correlation of VD with age or refractive error but moderate to high correlation with intraocular pressure, time of initial diagnosis, mean deviation, ganglion cell complex, peripapillary retinal nerve fiber layer thickness, cup to disc ratio, and rim area. Among the 14 individual features of macular VD, whole VD in the SL had the best diagnostic accuracy (77.6%) as measured by the area under the ROC.

CONCLUSION

OCTA detects glaucomatous damage by measuring the macular vessel density in the superficial and deep retinal vascular plexus. It can be an additional diagnostic tool to detect glaucoma independently of the optic nerve.

Macular Vessel Density in Glaucomatous Eyes With Focal Lamina Cribrosa Defects

PURPOSE

To compare optical coherence tomography angiography (OCTA) measured macular vessel density and spectral domain optical coherence tomography (SDOCT) measured macular ganglion cell complex (GCC) thickness in primary open-angle glaucoma eyes with and without focal lamina cribrosa (LC) defects.

METHODS

In this cross-sectional, case-control study of patients with primary open-angle glaucoma, 46 eyes of 46 patients with LC defects and 54 eyes of 54 patients without observable LC defects were included. OCTA and SDOCT imaging were performed on the same day by the same operator. Perimetry and swept-source OCT testing used to identify LC defects were conducted within 6 months of OCTA and SDOCT testing. Global and local parafoveal vessel density and macular GCC thickness were compared between study groups.

RESULTS

Glaucoma severity was similar between groups (SAP mean deviation=-5.63 and -4.64 dB for eyes with and without LC defects, respectively; P=0.40). Global and local measured parafoveal vessel density was similar between groups (all P≥0.11). GCC focal loss volume was higher in eyes with LC defects than eyes without LC defects (7.2% and 4.97%, respectively; P=0.03). In addition, GCC focal loss volume was topographically related to defect location in LC defect eyes.

CONCLUSIONS

Although OCTA macular vessel density was not significantly different between eyes with and without LC defects, focal GCC loss in eyes with LC defects was different. This highlights the importance of not relying solely on vessel density measurements for determining macular changes for diagnosing and detecting glaucomatous progression.

Quantitative changes in flow density in patients with adult-onset foveomacular vitelliform dystrophy: an OCT angiography study

PURPOSE

To quantitatively compare the flow density, the retinal thickness, and the area of the foveal avascular zone (FAZ) between patients with adult-onset foveomacular vitelliform dystrophy (AOFVD) and a healthy controls.

METHODS

Thirteen eyes (eight patients) with AOFVD and 13 matched eyes (13 patients) without any ocular pathology were included in this study. A 6 × 6 mm optical coherence tomography angiography (OCTA) scan was performed for every included eye. The flow density (superficial retinal vascular layer, deep retinal vascular layer and choriocapillary layer), retinal thickness and FAZ (superficial retinal vascular layer and deep retinal vascular layer) were subsequently analyzed.

RESULTS

The mean flow density was decreased in the AOFVD patients in all measured vascular layers. The difference from the control group was statistically significant in the parafoveal sector of the deep retinal vascular layer (P = 0.02), and a clear trend was found in the superficial retinal vascular layer (P = 0.05). Both groups had comparable FAZs in the superficial and deep retinal vascular layers. The retinal thickness values were higher in the fovea (P = 0.840) and lower in the parafoveal sectors (P = 0.125). The difference was significant in the superior parafoveal sector (P = 0.034).

CONCLUSIONS

Flow densities as measured by OCTA are decreased in the superficial retinal vascular layer and the deep retinal vascular layer in patients with AOFVD. These findings could be helpful for diagnosing and understanding the pathogenesis of this disease.