A. Yasin Alibhai

Long-term Progression of Type 1 Neovascularization in Age-related Macular Degeneration Using Optical Coherence Tomography Angiography

PURPOSEnTo analyze the long-term growth patterns of type 1 neovascularization (NV) in eyes with age-related macular degeneration (AMD) receiving anti-vascular endothelial growth factor (VEGF) therapy.nnnDESIGNnRetrospective cohort study.nnnMETHODSnPatients were enrolled from 2 eye centers and underwent optical coherence tomography angiography (OCTA) imaging with follow-up greater than 1 year. Choroidal neovascularization (CNV) was manually segmented on OCTA images and compared between time points. CNV growth was subdivided into 3 categories based on OCTA area measurement: CNV doubling, modest growth of less than 50%, and shrinkage. These growth rates were correlated with OCTA morphologic features.nnnRESULTSnForty-one eyes were analyzed. Mean CNV area was 1.60 ± 1.84xa0mm2 at baseline and 1.80 ± 1.84xa0mm2 at 1 year. Thirty-three eyes (80%) displayed an increase in CNV area at 1 year with a mean increase of 0.20 ± 0.38xa0mm2 (Pxa0= .001). Eleven eyes (27%) underwent CNV doubling, 19 eyes (46%) illustrated modest growth, and 6 (15%) showed shrinkage. Anatomic features including a capillary fringe (odds ratio [OR]xa0= 5.3, Pxa0= .036) and immature lesion morphology (ORxa0= 4.2, Pxa0= .015) were significantly associated with CNV doubling. CNV growth occurred in 3 predominant patterns: symmetric growth, asymmetric growth, and finger-like projections, which reflected the orientation of expansion of CNV. Symmetric and asymmetric growth together correlated with greater frequency of CNV doubling (ORxa0= 15, Pxa0= .0048).nnnCONCLUSIONnOCTA provides noninvasive measurement of the area of neovascular lesions in AMD. Sustained growth of type 1 NV can be identified in the majority of lesions (80%) that display characteristic patterns of progression despite ongoing anti-VEGF therapy.

Quantifying Microvascular Changes Using OCT Angiography in Diabetic Eyes without Clinical Evidence of Retinopathy

ObjectivenTo compare quantitative OCT angiography (OCTA) parameters of macular ischemia in diabetic eyes without retinopathy with those in healthy nondiabetic controls.nnnDesignnCross-sectional study from August 2014 through June 2017.nnnSubjectsnThirty-nine eyes of 39 diabetic patients without clinical evidence of diabetic retinopathy and 40 eyes of 40 healthy nondiabetic subjects.nnnMethodsnSubjects underwent OCTA imaging using prototype AngioVue software (RTVue XR Avanti). Analyses of the foveal avascular zone (FAZ) and vasculature surrounding the FAZ were performed on the automatically generated en face OCTA images of the superficial and deep retinal vasculatures using vessel-based and FAZ-based metrics.nnnMain Outcome MeasuresnComparison of measurements made in the superficial and deep retinal capillary plexuses of diabetic eyes and normal eyes.nnnResultsnFAZ-based analysis revealed statistically significant differences between diabetic and normal eyes in FAZ area (superficial and deep layers), perimeter (superficial layer), major axis length (superficial layer), and minor axis layer (superficial and deep layers). Vessel-based analysis revealed statistically significant differences in the binarized flow index (superficial and deep layers), both including and excluding the FAZ area.nnnConclusionsnQuantitative OCTA parameters reveal subclinical macular ischemia at both the superficial and deep retinal capillary plexuses in diabetic eyes that do not manifest clinical retinopathy. Vessel-based and FAZ-based metrics applied to OCTA images may serve as effective tools for screening and disease monitoring in patients with diabetes without clinical evidence of retinopathy.

Parafoveal Retinal Vessel Density Assessment by Optical Coherence Tomography Angiography in Healthy Eyes

BACKGROUND AND OBJECTIVEnTo assess variability in vessel density (VD) measurements across three optical coherence tomography angiography (OCTA) devices to identify a methodology that offers the least amount of variation in VD, and to assess the effect of averaging of multiple scans on VD variability.nnnPATIENTS AND METHODSnFifteen eyes of eight healthy individuals were imaged consecutively on three OCTA devices. Segmentations at the superficial, deep, and full retinal layers were generated. Repeat scans for each retinal layer were registered and averaged to generate one OCTA image. Two different automated thresholding techniques were used to calculate vessel area density (VAD) from binarized images and vessel skeleton density (VSD) from skeletonized images. Vessel length, a linear measure of the combined lengths of vessels, was calculated. Foveal avascular zone (FAZ) area was measured.nnnRESULTSnAll three OCTA devices were significantly different (P < .0001). This finding remained after averaging images (P < .0001). VSD was more repeatable within a device but less reproducible across devices. Conversely, VAD demonstrated less repeatability but greater reproducibility. Differences in VSD between devices were systematic and attributable to differences in resolution. Vessel length, unaffected by resolution, demonstrated no significant differences between the devices (P > .107). There was no significant difference in FAZ area across devices (P = .51). After averaging images, VD was significantly different from the single images for each device and plexus (P < .05) but remained within 1% of the value of a single scan.nnnCONCLUSIONSnOCTA devices show variability in VD for healthy individuals. With greater repeatability, VSD appeared useful for following a patient on one device. VAD and vessel length seemed ideal for comparing vessel parameters between OCTA devices. After averaging multiple scans, VSD remained within 1% of a single scan, for which clinical significance remains to be determined. Caution is advised when comparing quantitative analyses across OCTA devices. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:S5-S17.].

Swept Source Optical Coherence Tomography: a Review

Purpose of ReviewIn this review, we shall attempt to explain the physics behind swept source-optical coherence tomography (SS-OCT), the advantages and disadvantages of SS-OCT when compared with spectral domain-optical coherence tomography (SD-OCT), and the current clinical applications of SS-OCT.Recent FindingsSS-OCT offers improvements in visualizing the vitreous, retina, choroid, and sclera. The increased scan speeds, decreased signal attenuation, and deeper tissue penetration make SS-OCT ideal for capturing wide fields of view and for studying structures below the RPE, especially the choroid.SummarySS-OCT is an exciting new technology offering enhanced visualization of ocular structures. However, its everyday clinical utility remains unclear.

Abstract: First Approaches Towards Automatic Detection of Microaneurysms in OCTA Images

We investigated automatic detection of micro aneurysms in optical coherence tomo-graphy angiography. Data of two patients was gathered at the New England Eye Center. Patients with diabetic retinopathy were imaged on an Optovue Avanti device.

Diagnosing Choroidal Neovascularization in Asymptomatic Individuals Using Optical Coherence Tomography Angiography

Optical coherence tomography angiography (OCTA) is a noninvasive, rapid imaging technique that generates angiographic images without intravenous dye injections. Cross-sectional studies have described the presence of asymptomatic choroidal neovascularization (CNV) in patients with intermediate age-related macular degeneration (AMD). This case report describes the OCT features on longitudinal follow-up of a patient who started with unilateral asymptomatic CNV and eventually developed symptomatic exudative AMD. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:596-598.].