Spacing between the large vessels in the superficial and deep retinal layers had superior diagnostic performance than overall vessel density.

A novel implementation of local fractal dimension to calculate vessel density and FAZ area was demonstrated. Age did not impact vessel density but sectoral analyses showed greater vessel density in the inferior zone.

Citation: Kumar RS, Anegondi N, Chandapura RS, et al. Discriminant function of optical coherence tomography angiography to determine disease severity in glaucoma. Invest Ophthalmol Vis Sci. 2016;57:6079-6088. DOI:10.1167/iovs.16-19984 PURPOSE. To determine the discriminant function of optical coherence tomography angiography (OCTA) by disease severity in glaucoma.METHODS. In this prospective, observational cross-sectional study, all subjects underwent visual fields, retinal nerve fiber layer (RNFL) measurements, and OCTA imaging. Local fractal analysis was applied to OCTA images (radial peripapillary capillaries [RPC] layer). Vessel density en face and inside the disc and spacing between large and small vessels were quantified. Stepwise logistic regression was performed and a glaucoma severity score (range, 0-1: 0, normal; 1, severe glaucoma) was developed by using global and regional (superotemporal [ST], inferotemporal [IT], temporal, superonasal [SN], inferonasal, and nasal) vascular parameters. Glaucoma severity score was compared with visual field and RNFL indices. RESULTS.One hundred ninety-nine eyes (112 subjects) with glaucoma (28 eyes preperimetric; 83 early, 43 moderate, and 45 severe glaucoma) and 74 normal (54 subjects) eyes were enrolled. Preperimetric and glaucomatous eyes had significantly altered (P < 0.001) global vascular parameters as compared to normal; regionally, ST, then SN and IT sectors (in that order) showed more change in glaucomatous eyes. Vascular parameters showed better discriminant ability (area under the curve [AUC], sensitivity, and specificity of 0.70, 69.2%, and 72.9%, respectively) than structural parameters between normal and preperimetric glaucomatous eyes. Vascular parameters had comparable AUC (P > 0.05) to visual fields for perimetric glaucoma. Glaucoma severity score identified preperimetric glaucoma and early glaucoma better than did visual fields.CONCLUSIONS. Vascular parameters could be a useful adjunct tool to evaluate/diagnose glaucoma. Longitudinal studies are needed to determine their use in early detection and prognostication.Keywords: optical coherence tomography, glaucoma, visual field, angiography G laucoma is the leading cause of irreversible blindness worldwide.1,2 It is characterized by progressive degeneration of the optic nerve and loss of retinal ganglion cells, with corresponding visual field (VF) defects on standard automated perimetry.1,2 While raised intraocular pressure (IOP) is currently the only known modifiable risk factor for glaucoma, there is evidence that vascular insufficiency in the optic nerve head (ONH) also plays an important role in the pathogenesis of glaucoma.3-5 Currently, a number of methods are available for measuring ONH perfusion.6-11 Fluorescein angiography is invasive. It provides only superficial ONH perfusion and not deep perfusion.6 Noninvasive methods such as laser Doppler flowmetry and laser speckle flowgraphy have demonstrated decreased ONH perfusion in glaucomatous eyes, but have moderate repeatability.8,10 Doppler O...

Projection artifacts (PAs) affect the quantification of vascular parameters in the deep layer optical coherence tomography (OCT) angiography image. This study eliminated PA and quantified its effect on imaging. 53 eyes (30 subjects) of normal Indian subjects and 113 eyes (92 patients) of type 2 diabetes mellitus with retinopathy (DR) underwent imaging with a scan area of 3 mm × 3 mm. In this study, a normalized cross-correlation between superficial and deep layer was used to remove PA in deep layer. Local fractal analysis was done to compute vascular parameters such as foveal avascular zone area (mm ), vessel density (%), spacing between large vessels (%) and spacing between small vessels (%). Before PA removal, vessel density for mild nonproliferative (NPDR), moderate NPDR, severe NPDR and proliferative DR were 42.56 ±1.69%, 40.69 ±0.72%, 37.34 ±0.85% and 35.61 ±1.26%, respectively. After artifact removal, vessel density was 28.9 ±1.22%, 29.9 ±0.56%, 26.19 ±0.59% and 24.02 ±0.94%, respectively. All the vascular parameters were statistically significant (P <.001) between normal and disease eyes, irrespective of superficial and deep retinal layers. Parafoveal sectoral analyses showed that temporal zone had the lowest vessel density and may undergo DR-related changes first. The current approach enabled rapid and accurate quantitative interpretation of DR eyes, without PA.

Vessel density showed good repeatability among the three devices, although there were differences in vessel parameters between the devices. Also, vessel parameters changed significantly after Frangi filtering. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:488-496.].

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Purpose:To evaluate the association between retinal and choroidal thickness and volume along with choroidal vessel volume in children using optical coherence tomography (OCT) images.Methods:113 normal eyes of children ranging from 5-17 years of age were imaged with a clinical OCT scanner (Optovue Inc., Fremont, USA). The retina, choroid and choroidal vessels were automatically segmented with algorithms. Parameters evaluated were thickness and volume. Location specific analyses of thickness were also performed at a distance of 2.5 mm from foveal center. Multivariate analyses of variance were used to analyze the effect of age and myopia. Manual segmentation of the fovea and subfoveal choroid thickness was also performed to compare with the algorithm segmentation.Results:There was excellent agreement between manual and automatic segmentation (intra-class correlation of 0.95). Within the same eye, total retinal and choroid thickness of nasal and temporal location were significantly lower than the superior and inferior thickness (P < 0.0001). With age (P = 0.026) and myopia (P < 0.001), foveal thickness increased. Choroid volume, vessel volume and temporal choroid thickness increased with increasing myopia (P < 0.05). There was significant positive correlation between choroid volume and retinal volume (r = 0.62, P < 0.0001), choroid volume and vessel volume (r = 0.48, P < 0.0001), and with foveal thickness (r = 0.31, P = 0.009). Choroid vessel volume also showed significant positive correlations with the other metrics (P < 0.05).Conclusion:Retinal and choroidal structural features were quantified simultaneously from OCT images. Magnitude of myopia had a greater effect on retino-choroid features than age in children.

BACKGROUND AND OBJECTIVE: To compare the vascular parameters derived from optical coherence tomography angiography (OCTA) and fundus fluorescein angiography (FFA) images. PATIENTS AND METHODS: Twenty-two eyes of 22 patients were imaged with OCTA and FFA. FFA images were cropped to the same dimension as OCTA images after registration. Vessel enhancement using a Frangi filter and local fractal analysis was applied to the superficial layer of the OCTA and cropped FFA images. Foveal avascular zone (FAZ) area, vessel density, spacing between large vessels, and spacing between small vessels were quantified. RESULTS: FAZ area was similar between original OCTA, Frangi-filtered OCTA, and FFA images (P = .32). Actual OCTA images had significantly higher vessel density (35.2% ± 1.45%, P < .001) than Frangi-filtered OCTA images (29.8% ± 0.78%) and Frangi-filtered FFA images (25.5% ± 2.41%). Spacing between large vessels was significantly lower in original OCTA images (31.9% ± 1.47%, P < .001) than Frangi-filtered OCTA images (36.8% ± 1.24%) and Frangi-filtered FFA images (60.1% ± 2.68%). Further, FFA images had significantly lower spacing between small vessels (14.4% ± 0.43%, P < .001) than original OCTA images (32.7% ± 1.03%) and Frangi-filtered OCTA images (33.4% ± 0.81%). CONCLUSION: FAZ area was similar between OCTA and FFA, independent of vessel enhancement. However, vessel enhancement improved the agreement of vascular parameters between OCTA and FFA images of the same eye. [ Ophthalmic Surg Lasers Imaging Retina . 2018;49:e175–e181.]