Solar retinopathy-correlation between adaptive optics and spectral domain optical coherence tomography with visual acuity.

BACKGROUND: To study the characteristics of photoreceptors on adaptive optics (AO) in patients of solar retinopathy and its correlation to changes in spectral domain optical coherence tomography (SDOCT) and visual acuity. METHODS AND MATERIAL: This is a cross-sectional observational study of six eyes of five patients with clinically diagnosed solar retinopathy. Five age-matched controls were included for comparison. A flood-illuminated adaptive optics retinal camera (AO; rtx1, Imagine Eyes, Orsay, France) was used to image the photoreceptors and a spectral domain optical coherence tomography (SDOCT; Spectralis™ Heidelberg Engineering, Germany) was used to study the retinal layers in these patients. The corrected distance visual acuity (CDVA) was assessed using Snellen's chart. RESULTS: Defects on the SDOCT were smaller (0.25 to 0.75°) at the fovea compared with AO (more than 1°). The cone mosaic was preserved beyond 1°. The cone count from the foveal center at 0.75, 1, 2, and 3° was decreased in all patients of solar retinopathy (mean value 5352) compared with age-matched controls (mean value 15693). A corresponding increase in spacing (mean value 19.13) compared with controls (mean value 9.34) was also observed. The CDVA ranged from 20/30 to 20/80. There was no statistically significant relationship between cone density, at any of the eccentricities measured, with CDVA or OCT defect (p > 0.05, for all). CONCLUSIONS: Adaptive optics is a sensitive and accurate tool to analyze photoreceptor damage in solar maculopathy. It can be used as an adjunct for better understanding of the pathology and to observe or predict changes in these patients.

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.

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.

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.

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.

Spontaneous Closure of a Full-Thickness Stage 2 Idiopathic Macular Hole without Posterior Vitreous Detachment.

OBJECTIVE: We report a 50-year-old female patient with a stage 2 idiopathic macular hole that closed spontaneously. METHOD: The case is presented on the basis of an observational case report. RESULTS: The stage 2 idiopathic macular hole closed spontaneously in 6 weeks with a lamellar defect in the outer retina due to the formation of the bridging retinal tissue, but without any evidence of the common mechanisms of spontaneous closure such as posterior vitreous detachment or epiretinal membrane formation.

Surgical management of optic disc pit maculopathy with outer retinal hole.

OBJECTIVE: To report the successful outcome of a rare optic pit-associated maculopathy with an outer retinal hole following 23 G vitrectomy, internal limiting membrane (ILM) peeling and fluid-gas exchange without additional endolaser. METHOD: Interventional case report. RESULTS: This case report documents a 56-year-old male patient with complaints of progressive diminution of vision in the right eye more than in the left eye due to an optic disc pit with an outer retinal hole and a cataract. Optical coherence tomography confirmed the presence of an outer retinal hole. The case report shows the successful outcome of a rare optic pit-associated maculopathy with an outer retinal hole and a cataract following phacoemulsification with 23 G vitrectomy, ILM peeling and fluid-gas exchange without additional endolaser.