Quantitative evaluation of optical coherence tomography angiography images of diabetic retinopathy eyes before and after removal of projection artifacts.

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 (mm2 ), 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.

An automated framework to quantify areas of regional ischemia in retinal vascular diseases with OCT angiography.

In this observational and cross-sectional study, capillary nonperfusion (CNP) and vascular changes in branch retinal vein occlusion (BRVO, sample size [n] = 26) and choroidal neovascularization (CNV, n = 29) were evaluated. Subjects underwent imaging using Optical coherence tomography angiography (Angiovue OCTA, RTVue XR, Optovue Inc., Fremont, California). Local fractal analysis was applied to the OCTA images of superficial, deep and choriocapillaris layer. CNP area (BRVO eyes) and vascular parameters were computed using local fractal-based method. Sensitivity and specificity of vascular parameters were assessed with receiver operating characteristics curve. Automated CNP area showed excellent agreement with manually quantified CNP areas in both superficial (intraclass coefficient [ICC] = 0.96) and deep (ICC = 0.96) layers. BRVO eyes showed significantly altered (P < .05) vascular parameters in both superficial and deep layer as compared to normal eyes (n = 30). CNVM eyes had significantly higher capillary free zones (P < .001) as compared to normal eyes. In normal vs BRVO eyes, vessel density and spacing between the large vessels had similar area under the curve (AUC) (P > .05) in both superficial (0.97 and 0.97, respectively) and deep layer (0.99 and 0.98, respectively). Further, capillary free zones showed high AUC (0.92) in differentiating CNV eyes from normal eyes.

UNREPORTED SIDE EFFECT OF INTRAVITREAL DICLOFENAC IN CHRONIC DIABETIC MACULAR EDEMA.

PURPOSE: To evaluate the safety and efficacy of intravitreal diclofenac sodium. METHODS: A 61-year-old male with persistent diabetic macular edema was treated with 450 µg of intravitreal diclofenac sodium (systemic preparation). RESULTS: Postinjection Day 1, the spectral domain optical coherence tomography showed irregular vitreoretinal interface with wrinkling and separation of the internal limiting membrane from the nerve fiber layer with homogeneity of the inner layers. At 1 month, the compactness of the retinal layers was restored. Complete resolution of the cystoid macular edema was seen. At 1 year, there was mild flattening of the foveal depression with epiretinal membrane. CONCLUSION: Various studies have shown the safety and efficacy of intravitreal diclofenac without any reported side effect. We report the inner retinal toxicity in the form of cystic spaces and splitting of internal limiting membrane from nerve fiber layer on the first follow-up day, postinjection, which resolved over a period of 1 month. Further studies are needed to assess the safety of intravitreal diclofenac sodium.

Linking Retinal Microvasculature Features With Severity of Diabetic Retinopathy Using Optical Coherence Tomography Angiography.

PURPOSE: To correlate retinal vascular features with severity and systemic indicators of diabetic retinopathy (DR) using optical coherence tomography angiography (OCTA). METHODS: A total of 209 eyes of 122 type 2 diabetes mellitus patients with DR and 60 eyes of 31 normal Indian subjects underwent OCTA imaging. The diabetic retinopathy patients were graded as having either nonproliferative diabetic retinopathy (NPDR: mild, moderate, and severe NPDR using Early Treatment Diabetic Retinopathy Study classification) or proliferative diabetic retinopathy (PDR). Local fractal analysis was applied to the superficial and deep retinal OCTA images. Foveal avascular zone area (FAZ in mm2); vessel density (%); spacing between large vessels (%); and spacing between small vessels (%) were analyzed. Sensitivity and specificity of vascular parameters were assessed with receiver operating characteristics (ROC) curve. RESULTS: Normal eyes had a significantly lower FAZ area, higher vessel density, and lower spacing between large and small vessels compared with DR grades (P < 0.001). In the superficial layer, PDR and severe NPDR had higher spacing between large vessels than mild and moderate NPDR (P = 0.04). However, mild NPDR had higher spacing between the small vessels (P < 0.001). Spacing between the large vessels in the superficial retinal layer correlated positively with HbA1c (r = 0.25, P = 0.03); fasting (r = 0.23, P = 0.02); and postprandial (r = 0.26, P = 0.03) blood sugar. The same spacing in the deep retinal vascular plexus had the highest area under the ROC curve (0.99 ± 0.01) and was uniformly elevated in all diabetic eyes (P > 0.05). CONCLUSIONS: Spacing between the large vessels in the superficial and deep retinal layers had superior diagnostic performance than overall vessel density.

Monitoring neovascularization in aggressive posterior retinopathy of prematurity using optical coherence tomography angiography.

We describe the use of optical coherence tomography angiography (OCTA) in detecting and monitoring regression of the neovascular complex (NVC) in a case of aggressive posterior retinopathy of prematurity (AP-ROP). A premature Asian Indian girl with AP-ROP underwent laser photoablation at 26 days of life. Persistent NVC at the posterior border of the lasered retinal bed was detected clinically. On en face spectral domain optical coherence tomography (SD-OCT) and OCTA, the NVC appeared as an arborizing vascular net in the superficial capillary plexus. The deep capillary plexus and outer retinal layers showed corresponding flow outlines that suggested deeper extensions of the lesion. Supplemental laser treatment of the NVC was performed. Ten days later repeat en face SD-OCT and OCTA of the identical retinal location revealed that the vascular tortuosity and dilatation had reduced and that the flow lesions in the deeper layers were undetectable. Our findings in this case suggest that the NVC in AP-ROP extends beyond the superficial retina.

Characteristics and quantification of vascular changes in macular telangiectasia type 2 on optical coherence tomography angiography.

BACKGROUND: Macular telangiectasia type 2 (MacTel 2) is a bilateral idiopathic, rare neurodegenerative disease with alterations in the macular capillary network leading to vision loss and is the most common of three subtypes. Optical coherence tomography angiography (OCTA) is a non-invasive imaging modality which helps understand the complex pathological changes, and images the blood vessels across different layers based on their flow characteristics. METHODS: A cross-sectional study was conducted on 56 eyes of Asian Indian eyes of 28 consecutive patients with MacTel 2 studied during a 3-month period in a tertiary eye care hospital of South India. Clinically diagnosed cases of MacTel 2 underwent fundus photography, spectral domain OCT and OCTA. Fluorescein angiography was performed only when clinically indicated. Mean capillary density was calculated using a MATLAB-based automated software. The images were thresholded and binarised to derive the mean value. RESULTS: The mean age at presentation was 60±5.2, with a female preponderance of 71.42%. Vascular network on OCTA shows an increase in the intervascular spaces with progressive capillary rarefaction and abnormal capillary anastomosis. The outer retina and choroid were involved during the later stages and showed a prominent vascular network. The mean capillary density of the superficial and deep layers was 39.99% and 39.03% as against 45.18% and 44.21% in the controls, respectively. There was a statistically significant difference between the two groups (p<0.01). There is a positive and statistically significant correlation between the superficial and deep layers. CONCLUSION: OCTA helps understand the pathology and disease progression better in MacTel 2.

Perivascular and Quadrant Nerve Fiber Layer Thickness and Its Relationship with Oxygen Saturation.

PURPOSE: To study whether there exists a relationship between retinal nerve fiber layer thickness and oxygen saturation and to identify whether perivascular thickness (pRNFL) or quadrant thickness (qRNFL) has a stronger correlation. METHODS: Patients without any detectable ocular abnormality on complete ophthalmic evaluation underwent non-invasive photo-spectrometric retinal oximetry on the Oxymap T1 retinal oximeter (Oxymap hf, Reykjavik, Iceland) and spectral-domain optical coherence tomography to determine if the pRNFL (Spectralis, Heidelberg, Germany) and the qRNFL (RtVue, Optovue) correlated with the measured light intensities and the calculated retinal oxygen saturations. RESULTS: 30 eyes of 30 patients (120 arterioles, 120 venules) were included in the study. The mean arteriolar saturations (%) were temporal: 84.5 (95% CI 82.7-86.3) and nasal: 93.5 (95% CI 91.0-95.8); venous saturations were temporal: 54.4 (95% CI 52.9-55.9) and nasal: 59.9 (95% CI 58.3-61.4). The mean pRNFL thickness (µm) around arterioles was temporal: 153.1 (95% CI 146-159) and nasal: 109.4 (95% CI 103-115); around venules it was temporal: 147.4 (95% CI 140-154) and nasal: 101.2 (95% CI 95-107). The oxygen saturations correlated significantly with pRNFL (arteriolar r = -0.514; p < 0.001 and venous r = -0.513; p < 0.001) but did not show a significant correlation with qRNFL values. CONCLUSION: This relationship between perivascular RNFL could be physiological or artifactual. If physiological, it would explain and form the basis of altered oxygen saturation in a multitude of diseases. If artifactual, it would necessitate the incorporation of a pRNFL correction. However, the results of this study enable us to expect increased saturation in areas of thinner RNFL or vice versa with the current methodology of retinal vessel oximetry as obtained by dual-wavelength photo-spectrometric fundus imaging.

Quantification of Vessel Density in Retinal Optical Coherence Tomography Angiography Images Using Local Fractal Dimension.

PURPOSE: To evaluate a fully automated local fractal dimension method to quantify vessel density and foveal avascular zone (FAZ) area in optical coherence tomography angiography (OCTA) images. METHODS: Fifty-two healthy Asian Indian eyes underwent imaging prospectively with OCTA system. Superficial and deep retinal vascular plexus was imaged. Local fractal analysis was applied to the OCTA images. A scan area of 3 × 3 mm was selected in the superficial and deep retinal layers. Foveal avascular zone area and vessel density were quantified in circular and sectoral zones around the fovea. A unique contour map of vessel density and dropout zones was developed to perform regional comparisons. RESULTS: Foveal avascular zone of superficial (0.35 ± 0.013 mm2) and deep (0.49 ± 0.012 mm2) retinal vascular plexus was segmented. The agreement between the manually segmented and local fractal dimension segmented FAZ area was 0.97 (95% confidence interval [CI]: 0.94-0.98) and did not change significantly with age (P = 0.94 and 0.21, respectively). The vessel density was greater in the deep than the superficial retinal vascular plexus (P < 0.0001). When the image was subdivided into sectors around the FAZ, inferior sector had greater vessel density than the others (temporal, superior, and nasal) in both superficial and deep retinal vascular plexus (P < 0.05). These observations were similar to recent studies on animal retinal vasculature map. CONCLUSIONS: 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.

Correlation of spectral-domain optical coherence tomography with fundus fluorescein angiography in an infant with retinal hamartomas.

PURPOSE: To describe the correlation between the surface morphology on spectral-domain optical coherence tomography (SD-OCT) and leakage pattern on fundus fluorescein angiography (FFA) in an infant with multiple retinal hamartomas. METHODS: An Asian Indian female infant was found to have 2 retinal lesions in the right eye and 1 in the left eye during Retcam (Clarity MSI, CA, USA) screening for retinopathy of prematurity at 45 weeks postmenstrual age. Spectral-domain optical coherence tomography on the hand-held OCT (Envisu 2300, Bioptigen, NC, USA) and FFA on the Retcam 3 were performed under monitoring in the office. RESULTS: Spectral-domain OCT detected all 3 lesions but only 1 lesion was detected on FFA. While this lesion had an irregular surface with overlying vitreoretinal (VR) traction on SD-OCT, the other 2 lesions not detected on FFA were smooth and had no VR traction. After a follow-up to 18 months corrected age, there was no change in the morphology of any of the lesions. CONCLUSIONS: It is possible to characterize retinal hamartomas in infants using SD-OCT and correlate them with FFA. Spectral-domain OCT examination can be used to diagnose and monitor lesions even if they are not detectable on angiography.