Ocular Coherence Tomography Angiography Research Articles

Vascular imaging findings in retinopathy of prematurity.

Retinopathy of prematurity (ROP) is a vascular disease among preterm infants involving incomplete or abnormal retinal vascularization and is a leading cause of preventable blindness globally. Measurements of ocular blood flow originating from a variety of imaging modalities, including colour Doppler imaging (CDI), fluorescein angiography (FA) and ocular coherence tomography angiography (OCTA), have been associated with changes in ROP patients. Herein, we discuss and summarize the relevant current literature on vascular imaging and ROP reviewed through December 2022. Differences in vascular imaging parameters between ROP patients and healthy controls are reviewed and summarized. The available data identify significantly increased peak systolic velocity (PSV) in the central retinal artery and ophthalmic artery as measured by CDI, increased vascular tortuosity as measured by FA, smaller foveal avascular zone (FAZ) as measured by FA and OCTA, and increased foveal vessel density (VD) and reduced parafoveal VD as measured by OCTA in ROP patients compared with controls. None of the above findings appear to reliably correlate with visual acuity. The studies currently available, however, are inconclusive and lack robust longitudinal data. Vascular imaging demonstrates the potential to aid in the diagnosis, management and monitoring of ROP, alongside retinal examination via indirect ophthalmoscopy and fundus photography.

Novel approach to Behçet's disease in the era of biologic agents.

This review aims to provide better understanding of modern modalities to investigate ocular symptoms of Behçet's disease in order to achieve appropriate management protocols and reduce irreversible visual loss. Current methods of diagnosing intraocular involvement in Behçet's disease gives clue to early diagnosis. In addition to standard ocular examination and fluorescein angiography, new noninvasive methods include ocular coherence tomography (OCT) and OCT angiography provide early detection of macular and retinal involvement that can be treated early to improve the prognosis. Over the last decade, new multimodal imagings are becoming more accessible; therefore, rapid diagnosis can be made. In addition to newer approved biologic agents, ocular Behçet's disease is seen to be in better controlled with fewer complications.

Macular vascular features of different types of diabetic macular edema using ocular coherence tomography angiography- a comparative study

BackgroundTo compare the microvascular features of different subtypes of diabetic macular edema (DME) by optical coherence tomography angiography (OCTA).MethodsA cross-sectional study including treatment-naive patients with DME. Eyes were divided according to optical coherence tomography determined morphology into two groups: cystoid macular edema (CME) and diffuse retinal thickening (DRT), with further subdivision according to the presence of subretinal fluid. All patients underwent 3 × 3 and 6 × 6 mm OCTA scans of the macula to compare the foveal avascular zone (FAZ) area, vascular density (VD) of the superficial (SCP) and deep (DCP) capillary plexus and choriocapillaris flow (CF). Laboratory findings (HbA1C and triglyceride levels) were also correlated with the OCTA findings.ResultsThe study included 52 eyes, 27 had CME and 25 had DRT. There were no significant differences between the VD of the SCP (p = 0.684) and DCP (p = 0.437), FAZ of SCP (p = 0.574), FAZ of DCP (p = 0.563) and CF (p = 0.311). Linear regression analysis revealed that DME morphology was the strongest predictor for BCVA. Other significant predictors included HbA1C and triglyceride levels.ConclusionThe morphology of DME, irrespective of SRF, was most significantly correlated with BCVA in treatment-naive patients and CME subtype could be an independent predictor of poor BCVA in patients with DME.

Assessment of Retinal Vessels Density and Blood Flow Density in Patients with Primary Open Angle Glaucoma Using Ocular Coherence Tomography Angiography

Assessment of Retinal Vessels Density and Blood Flow Density in Patients with Primary Open Angle Glaucoma Using Ocular Coherence Tomography Angiography

Effect of Intravitreal Bevacizumab on the Optic Nerve Head perfusion in patients with Diabetic Macular Edema

Purpose: To find out the effect of Intravitreal Bevacizumab on optic nerve head perfusion using Ocular Coherence Tomography Angiography (OCTA) in patients with diabetic macular edema (DME). Study Design: Interventional case series Place and duration of study: Ophthalmology Department, Mayo Hospital, Lahore from June 2018 to January 2020. Methods: In this study 57 eyes of patients fulfilling the inclusion criteria were selected from the outpatient department. After informed consent, detailed history and ocular examination was performed. Baseline OCTAwas donein all cases. The patients received intravitreal Bevacizumab (1.25mg in 0.05ml). OCTA was repeated three weeks after injection. Both the pre and post injection ONH perfusion was compared and analyzed using SPSS. Demographic chracteristics like age and gender were calculated. Paired sample t-test was applied to check the significance of difference between pre and post injection values. P-value of <0.05 was considered significant. Results:There were 16(28.1%) males and 41(71.9%) females. Mean age of the patients was 53.54±7.00 years. Pre injection blood flow was 56.11 and post injection was significamtly reduced to 52.69. The mean difference between was 3.423 and confidence interval of the difference was (2.5755-4.2701). P-value 0.000 was <0.05 whichshowed significant reduction in perfusion of ONH. Conclusion:Intravitreal Bevacizumab decreases the optic nerve head blood flow and should be used with care in patients having reduced blood flow states and also in patients with advanced glaucomatous optic neuropathy.

The role of ocular coherence tomography angiography in the diagnosis of diabetic retinopathy and a comparison with the current gold standard fundus fluorescein angiography

Background: Diabetic retinopathy is a leading cause of preventable blindness in the world. Efficient and effective diagnosis and surveillance of diabetic retinopathy is of crucial importance to preserve the vision of patients. The FAZ (Foveal Avascular Zone) area is enlarged in patients of diabetic retinopathy. The purpose of this study was to evaluate the accuracy of OCT-A (Optical Coherence Tomography-Angiography) in delineating the FAZ area in cases of diabetic retinopathy and make a comparison with the findings of FFA (fundus fluorescein angiography) - the current gold standard.Subjects and methods: This was a comparative analytical study carried out at a tertiary care hospital in Lahore, Pakistan. A series of 50 patients, 30 males and 20 females with a mean age of 40 years were selected from the hospital outpatient department with history of five years of diabetic retinopathy. They were classified according to the ETDRS classification system into NPDR and PDR groups. The patients were booked for OCT-A, the scans were then observed for findings with a specific focus on the area of the FAZ at the level of the superficial capillary plexus. The patients then underwent same day FFA the current gold standard modality for diabetic retinopathy, thereafter a comparison between the mean area of the FAZ in both the modalities was made & documented. Data was analyzed using SPSS version 25.0. Results: The FAZ was easily distinguished by both FFA and OCT-A. The mean FAZ area was 0.62 mm2 on FFA and 0.69 mm2 on OCT-A. There was a statistically significant difference between the two means (p=0.002). Both the modalities had a Sensitivity of 100% at 0.44 and 0.48 cut-offs. OCT-A had a specificity of 91.9% and FFA had a Specificity of 89.2%.Conclusions: OCT-A proved to be an effective and accurate modality in delineating the FAZ area and detecting macular ischemia in patients of diabetic retinopathy in comparison to the current Gold-Standard FFA.

Optical Coherence Tomography Angiography in Healthy Adult Subjects: Normative Values, Frequency, and Impact of Artifacts.

Aim This cross-sectional study is aimed at identifying normative ocular coherence tomography angiography (OCTA) values in a cohort of healthy adult Jordanian individuals and assessing the prevalence of different image artifacts and their impact on quantitative OCTA measurements. Materials and Methods One hundred and eighty-one eyes from 100 healthy participants were included in this study. All participants underwent a comprehensive ophthalmological examination including best corrected visual acuity, slit lamp examination, and dilated fundoscopy. Swept-source OCTA images were obtained and analyzed for all 181 eyes. We recorded vascularity measurements and analyzed the prevalence and effect of ten different artifacts on superficial and deep retinal and choriocapillaris layer images. Results Sixty-two percent of the participants were men (n = 62), and 38% (n = 38) were women. The age of participants ranged between 24 and 75 years (mean 50.5 ± 10.92). The mean central macular thickness was 237.71 (±22.905) μm, and the mean choroidal thickness was 257.73 (±77.027) μm. Artifacts were present in 46.4% of the acquired scans. Images with artifacts had higher mean age (p = 0.03), lower image quality (p < 0.001), higher central vascular density (p < 0.001), and lower inferior vascular density (p < 0.001) compared to artifact-free tomographs. Motion artifact was the most common type, which was present in 29 (16%) of images, followed by blink artifact 18 (9.9%), and Z offset 8 (4.4%). Conclusion OCTA artifact detection and correction remains a challenging aspect of the diagnostic and follow-up process of patients with retinal pathologies. To our knowledge, this is the first study to examine the association between OCTA outputs and artifacts in healthy eyes. We report that in this cohort of normal individuals, images with artifacts had a significantly higher central vascular density (22.62 vs. 16.60) and a lower inferior vascular density (46.09 vs. 48.81). We also found that a significant increase in central vascular density is only present in images with Z offset artifact type (49.03). Motion artifact was the most common artifact seen in our series. However, we observed no alteration in quantitative parameters in images with motion artifacts.

Retinal findings of COVID-19 patients using ocular coherence tomography angiography two to three months after infection: Ocular appearance recovered COVID-19 patient

PurposeThe aim of this study was to evaluate the ocular disorders in COVID-19 patients, two to three months after infection. MethodsIn this cross-sectional, historically controlled study, fifty-one COVID-19 patients were compared with thirty-seven age, and gender-matched healthy individuals. After complete ophthalmological examination, all participants underwent peripapillary and macular optical coherence tomography, and optical coherence tomography angiography (OCTA) measurements (OptoVue Inc, Freemont, CA, USA). ResultsThe time between the initial onset of symptoms, and ophthalmologic examination was 63.31±15.21 (40–95 days). Ophthalmic examination of all the recovered COVID-19 patients was within normal range. None of the peripapillary and macular OCTA parameters were significantly different between the two groups with pairwise comparisons, but after adjusting for age, gender, axial length, and signal strength index (SSI), recovered COVID-19 eyes showed a significant increase in peripapillary retinal nerve fiber (RNFL) thickness, superficial, and deep macular vessel densities in parafoveal and perifoveal regions compared with healthy control eyes (p<= 0.05). Inner retinal thickness overall is higher in recovered COVID-19 eyes compared to healthy eyes after adjustment. ConclusionPatients with moderate-intensity SARS-CoV-2 pneumonia had altered peripapillary and macular vessel density compared to healthy subjects. Further investigation is warranted to analyze the correlation of these changes with disease severity as well as evolution of these changes over time.

OCT retinal imaging as differential diagnostic tool between Parkinson disease and essential tremor

AbstractPurposeTo evaluate neuroretinal measurements in Parkinson disease (PD) and essential tremor (ET) patients, and to compare results with healthy controls.MethodsA total of 214 subjects (214 eyes) were included in our study (146 healthy controls, 42 PD patients and 26 ET patients). Retinal examination in the peripapillary zone and the macular zone (retinal nerve fiber layer [RNFL] and ganglion cell layer [GCL] thickness) was performed for each subject using Swept source ocular coherence tomography (OCT) Triton and Spectralis OCT. Additionally, macular vascularization was analysed with OCT angiography (OCT‐A).ResultsA significant reduction in the peripapillary RNFL and CGL was observed in PD patients compared to ET patients (p &lt; 0.001). Also, the RNFL in the macular area was significantly thinner in PD patients compared to ET (p &lt; 0.001).ET patients showed significant thinning in both GCL and RNFL compared with controls only in nasal sectors (p &lt; 0.001) Although vascularisation showed higher density in healthy controls compared to PD and ET, this parameter did not reach significance levels. According to the correlation analysis, global OCT angiography was associated inversely with disease duration in PD (r = −0.600; p = 0.018). Logistic regression analysis was performed, obtaining two linear discriminant functions (LDF) for differencing PD from ET or controls. These LDF included density of OCT‐A and GCL macular thickness (for Triton OCT) and RNFL peripapillary thickness (for Spectralis). They yielded a receiver operating characteristic curve (ROC) of 0.796 (p = 0.020) for Triton OCT; and 0.627 (p = 0.033) for Spectralis OCT.ConclusionsBoth PD and ET present retinal thinning compared with healthy controls. However, compared to ET, PD has a higher decrease affecting more areas of the RNFL and GCL, which might help differentiate both diseases. Considering the fact that OCT test is non‐invasive, quick and mostly available in every ophthalmological clinic, it could be considered as a potential tool for differential diagnosis between these two entities.

Associations between optic disc characteristics and macular choroidal microvasculature in young patients with high myopia.

This study aimed to examine changes to optic disc characteristics and macular choroidal microvasculature, and their relationships in young patients with high myopia (HM). A total of 90 patients were enrolled in this cross-sectional study. Based on their refractive power, the patients were divided into three groups: 27 in the control group, 34 in the HM group and 29 in the extremely high myopia group. Images of each patient's macula and optic disc were taken by ocular coherence tomography angiography. The macular choroidal and retinal thickness, capillary vessel density and capillary flow area were measured using Matlab software. Parapapillary atrophy (PPA) and the ovality index (OI) obtained from the scanning laser ophthalmoscopy images and the degree of optic disc tilt obtained from the optic nerve head ocular coherence tomography B-scans were analysed by Image J and Matlab software. The PPA area, OI and degree of optic disc tilt were significantly different among the three groups (all p ≤ 0.001). The macular choroidal thickness and microvasculature were significantly different among the three groups (all p < 0.05). Macular choroidal thickness was significantly correlated with PPA area and the degree of optic disc tilt (r=-0.331, p=0.003; r=-0.394, p=0.001, respectively). Macular choroidal capillary vessel density and choriocapillaris flow area were associated with PPA area (r=-0.251, p=0.047; r=-0.326, p=0.009, respectively). PPA area, OI and the degree of optic disc tilt were increased in patients with HM, and these changes were correlated with macular choroidal thickness and choroidal microvasculature.

Update on imaging modalities for ocular surface pathologies.

To discuss recent studies of imaging modalities for ocular surface pathologies. Novel micro-ocular coherence tomography technology can produce high-resolution images of corneal cellular and nervous structures. Ocular coherence tomography angiography can aid in detecting early stage limbal stem cell deficiency. Several studies used in vivo confocal microscopy to evaluate corneal nerve metrics and morphology. The applications of anterior segment optical coherence tomography, anterior segment optical coherence tomography angiography, ultrasound biomicroscopy, and in vivo confocal microscopy are useful technologies for imaging the ocular surface. Several studies have used artificial intelligence in combination with imaging technologies to create reliable and effective systems to detect and visualize ocular surface pathologies. AS OCT continues to be a key imaging tool and future development of μOCT technology may further enhance its utility.

Clinical course of choroidal neovascular membrane in West Nile virus chorioretinitis: a case report

BackgroundThis report describes the clinical course of choroidal neovascular membrane (CNV) in West Nile virus-associated chorioretinitis.Case presentationA 28-year-old Italian woman was referred to our institution because of reduced visual acuity in the left eye dating back 4 months. A diagnosis of retinal vasculitis in the right eye and chorioretinitis with CNV in the left eye was made. A complete workup for uveitis revealed positivity only for anti-West Nile virus immunoglobulin M (IgM), while immunoglobulin G (IgG) was negative. Whole-body computed tomography and nuclear magnetic resonance imaging of the brain were also negative. Therefore, the patient was treated with a combination of oral prednisone (starting dose 1 mg/kg per day) and three intravitreal injections of bevacizumab 1.25 mg/0.05 ml, 1 month apart. Fourteen days from starting corticosteroid therapy and after the first intravitreal injection, the patient experienced increased visual acuity to 0.4. Response to therapy was monitored by clinical examination, ocular coherence tomography (OCT), OCT angiography and retinal fluorescein angiography. Three months later, resolution of CNV in the left eye was achieved and no signs of retinal vasculitis were detected in the right eye, while serum IgM for West Nile virus turned negative and IgG positive.ConclusionCNV may be a complication of West Nile virus-associated chorioretinitis, and only subclinical retinal vasculitis may also be found even in non-endemic regions.

Impact of cardiometabolic factors on retinal vasculature: A 3 × 3, 6 × 6 and 8 × 8-mm ocular coherence tomography angiography study.

Ocular coherence tomography angiography (OCTA) is available in varying size and resolution. We sought to characterise associations of cardiometabolic factors with retinal microvascular changes using 3 × 3, 6 × 6 and 8 × 8-mm OCTA scans to determine differences in detection with varying scan size. Cross-sectional study of 247 cardiovascular patients from a single-centre tertiary-care hospital. Demographic, comorbidity and medication data were obtained. Patients underwent 3 × 3, 6 × 6 and 8 × 8-mm macula OCTA scanning using Carl Zeiss CIRRUS HD-OCT Model 5000. Angioplex and AngioTool software was used to quantify vascular parameters in the superficial capillary plexus. Increasing age, hypertension, dyslipidaemia, diabetes, chronic kidney disease, coronary artery disease and peripheral vascular disease were associated with reductions in vessel density, vessel perfusion, average vessel length and/or junction density in 3 × 3-mm OCTA (P < .05 for all). Conversely, smoking was associated with increased vessel density, vessel length and junction density in 3 × 3-mm OCTA (P < .05 for all). Associations of vessel abnormalities with cardiometabolic factors were progressively weakened and statistically attenuated in 6 × 6 and 8 × 8-mm OCTA scans. In multivariate analyses, dyslipidaemia remained an independent predictor of reduced vessel density, average vessel length and junction density (P < .05). Cardiometabolic factors are associated with multiple retinal microvascular changes in 3 × 3-mm OCTA scans. These associations were weakened and progressively attenuated in OCTA scans of larger 6 × 6 and 8 × 8-mm size. These findings advance our understanding of microcirculatory dysfunction and may have future implications for the screening and management of patients with cardiometabolic risk factors. Additional studies are required to further investigate these important associations.

The foveal avascular zone area in healthy eyes measured by ocular coherence tomography angiography using a full spectrum probabilistic algorithm.

Report the foveal avascular zone (FAZ) area imaged by OCT angiography (OCTA) using a full spectrum probabilistic algorithm in eyes of healthy individuals from Costa Rica without any ocular or systemic pathology. Retrospective chart review of consecutive healthy patients that were evaluated from January 2018 to October 2018 that underwent OCTA of the macular area. The OCTA consisted of a 10° × 10° cube of 512 A scans separated by 6µm each with an automated real time mode of 5. The FAZ area of the superficial vascular complex (SVC), the deep vascular complex (DVC), superficial vascular plexus (SVP), intermediate vascular plexus (IVP) and the deep vascular plexus (DVP) were measured manually by 2 different observers at 3 different times. A total of 234 eyes of 121 patients were included in this study. Mean age was 50years (range, 15-89), 85 patients (70%) were female. Inter- and intra-observer agreements were excellent. The mean FAZ areas in the different layers were 0.258 ± 0.0035 mm2 for the SVC, 0.205 ± 0.01 mm2 for the DVC, 0.415 ± 0.01 mm2 for the SVP, 0.305 ± 0.01 mm2 for the ICP and 0.420 ± 0.01 mm2 for the DCP. The mean FAZ areas in most of the measured layers increased with age and decreased with CMT. Gender and spherical equivalence were not correlated with FAZ area. Manual measurements of the FAZ imaged by OCT-A using a full spectrum probabilistic algorithm are widely reproducible both by the same observer and between observers. The FAZ increases with age and decreases with CMT in normal individuals.

Impact of Axial Eye Size on Retinal Microvasculature Density in the Macular Region.

Mechanical tissue stresses are important contributors to the increased risk of sight-threatening pathology in larger, more myopic eyes. The contribution of altered ocular vasculature to the development of this pathology is less well defined. The current study investigated the impact of eye size on the superficial vasculature of the macula. Subjects (n = 104) aged 18–50, with no history of ocular or vascular disease, or myopia control, were recruited from university staff and student populations in Australia and Hong Kong. Refractive error, ocular size, retinal morphology and vascular morphology were quantified through open field autorefraction, ocular biometry and ocular coherence tomography angiography. Morphology of the superficial retinal capillary plexus was assessed over a 3 × 3 mm fovea-centred area. Perfusion area and vessel length densities were analysed relative to axial eye length and retinal thickness. A significant inverse association was found between axial length and vascular density measures (perfusion area density r2 = 0.186, p < 0.001; and vessel length density r2 = 0.102, p = 0.001). Perfusion area and vessel length densities were reduced by 5.8% (p = 0.001) in the longest, relative to the shortest, eyes. The aggregated ganglion cell layer inner plexiform layer thickness was also inversely associated with eye size (r2 = 0.083, p = 0.003), and reduced, by 8.1% (p < 0.001), in the longest eyes. An inverse association of eye size and superficial retinal vasculature density, that is not simply explained by retinal expansion or image magnification factors, was confirmed. These data support the hypothesis that ongoing metabolic challenges may underlie the development of myopia-related and -associated pathology in larger eyes.

Repeatability of measuring the vessel density in patients with retinal vein occlusion: An optical coherence tomography angiography study.

To determine the repeatability of superficial vessel density measurements using Spectral domain Ocular coherence tomography angiography(SD-OCTA) in patients diagnosed with retinal vein occlusion(RVO). Prospective observational study. Patients who visited our retinal clinic from August 2017 to August 2018, diagnosed with RVO were recruited for the study. Two consecutive 3×3 mm pattern scans were performed using the Cirrus HD-OCT 5000 along with AngioPlex software (Carl Zeiss Meditec) in each eye by single skilled examiner. All scans were analyzed using en face OCTA images to measure vessel density (VD) automatically. For further analysis of the effect of central macular thickness(CMT), eyes were divided into two groups according to CMT of 400μm (Group 1: CMT > 400μm, Group 2: CMT < 400μm). To identify factors affecting the repeatability of VD measurements, linear regression analyses were conducted for the coefficient of variation (CV) of VD by investigating demographics and ocular variables. The intraclass correlation coefficient (ICC), coefficient of variation (CV) of VD measurements. A total of 57 eyes from 57 patients were examined: 35 eyes with BRVO and 22 eyes with CRVO. In all 57 eyes with RVO, the ICC and CV of the full VD(VD of 3mm diameter circle) were 0.800 and 10.61%, respectively. Univariate analyses showed that the mean CMT (B, 0.001; p<0.001) and mean ganglion cell-Inner plexiform layer (GC-IPL) thickness (B, -0.002; p = 0.020) were significant factors that affected the repeatability. Multivariate analyses of these two factors showed that only mean CMT was a significant factor. The ICC and CV of the full VD in group 1 (CMT > 400μm) were 0.348 and 22.55% respectively. In group 2 (CMT < 400μm), the ICC and CV of the full VD were 0.910 and 7.76%, respectively. The repeatability of VD measurement in eyes with RVO was reasonably comparable to previous studies. Repeatability of VD measurement was significantly affected by central macular thickness.

Comparison of different morphologies of choroidal neovascularization evaluated by ocular coherence tomography angiography in age-related macular degeneration.

The clinical implications of different morphologies of choroidal neovascularization (CNV), as evaluated by ocular coherence tomography angiography (OCTA) in neovascular age-related macular degeneration (nAMD), are lacking. To describe the morphology of CNV in nAMD using OCTA, and to compare the visual prognosis and other structural OCT biomarkers between different morphologic patterns. Retrospective cohort study. One hundred and forty eyes with nAMD treated with anti-vascular endothelial growth factor (VEGF). Patients were examined using OCTA prior to and at 3, 6 and 12 months after receiving anti-VEGF therapy. Best-corrected visual acuity (BCVA) and morphologic retinal features. Organized CNV was identified in 110/140 eyes (78.6%) using OCTA. These CNV complexes could be divided into three OCTA patterns: the 'medusa' pattern (n = 41), characterized by branching vessels radiating in all directions; the 'seafan' pattern (n = 43), characterized by branching vessels radiating to one side of the lesion; and the 'tangled' pattern (n = 26), characterized by globular entwined vessels without a main trunk. At baseline, the eyes with the tangled pattern were from younger patients (P = .031) with better BCVA (P = .007). There were also fewer intraretinal cysts (P = .021), less fibrovascular pigment epithelial detachment (P = .009), and more pachychoroid (P = .007) in eyes with the tangled pattern on OCT. At 12 months post-treatment, patients with the tangled CNV pattern also showed greater visual improvement than patients with the other two patterns (P = .049). Using OCTA, distinct morphologies of CNV in nAMD patients were identified. These different patterns might be useful predictors for the prognosis of nAMD patients after anti-VEGF therapy.

OCTA: A Practical Method of Image Averaging Using Adobe Photoshop Software.

To describe a method for averaging ocular coherence tomography angiography (OCTA) images using a commercially available photo editing software: Adobe Photoshop CC 2017. This single-center study assessed the feasibility of using Adobe Photoshop as an OCTA image averaging tool. Three 3.0 mm × 3.0 mm OCTA images from each eye were obtained using commercially available OCTA devices. Captured OCTA images were exported in high-resolution TIFF format, imported as an image stack, aligned using an automated function, and averaged by creating a Smart Object using Photoshop CC 2017 software. In conjunction with qualitative assessment, the main outcome of the study was image grader preferences with respect to clarity of the foveal avascular zone (FAZ), blood vessel delineation, and the ability to identify abnormal vasculature. After removing OCTA scans with significant image distortion, 25 sets of images were included in the analysis. Adobe Photoshop CC 2017 successfully aligned and averaged all images of the superficial and deep retinal plexuses that contained a minimum 40% overlap. Three independent retinal specialists found the averaged images to be slightly or definitely preferable to the original 87%, 89%, and 69% of the time with respect to clarity of the FAZ, clarity of blood vessel delineation, and the ability to identify abnormal vasculature, respectively. Adobe Photoshop CC 2017 is an excellent tool for image averaging, producing high-quality resulting OCTA images. As an easily accessible software, Photoshop has the potential for use in a diversity of pathological conditions. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:802-807.].

Hypoxia challenge test and retinal circulation changes - a study using ocular coherence tomography angiography.

Previous studies report that the response of retinal vessels to a decrease in oxygen (hypoxia) is vasodilation, thus increasing blood flow. We aimed to characterize the changes in retinal microvasculature induced by a mild hypoxia stress test in a healthy population, using ocular coherence tomography angiography (OCT-A) technology. Interventional repeated-measures study. The standardized hypoxia challenge test (HCT) was performed to all volunteers, according to the BritishThoracic Society protocol. Ocular coherence tomography angiography (OCT-A) was performed at three time-points (baseline, during HCT and 30' posthypoxia). Macular and peripapillary vessel densities were assessedusing the built-in software. To minimize bias, analysis was performed separately in right (OD) and left (OS) eyes. Repeated-measures anova and mean comparison analysis were used as statistical tests (stata v13). Studied population included 30 healthy subjects (14 women), with a mean age of 28.8±4.2 [range 22-37] years. Baseline vessel density increased in hypoxic conditions and subsequently decreased to near-baseline values in posthypoxia conditions. This pattern was observed for both eyes in both parafovea (OD: 55.3±2.3 to 56.7±1.9 to 55.8±1.9, p<0.05; OS: 56.9±2.1 to 57.9±1.9 to 57.3±1.7, p<0.05) and peripapillary (OD: 60.5±0.5 to 62.6±0.5 to 60.1±0.4, p<0.05; OS: 60.4±0.4 to 62.3±0.5 to 60.7±0.4, p<0.05) areas. To our knowledge, there are no published data specifically addressing mild hypoxia conditions and retinal microvasculature changes, using OCT-A. This pilot study may pave way to better understand vascular responses in disease setting.

Anterior segment ischemia: etiology, assessment, and management.

Anterior segment ischemia (ASI) is a potentially serious but rare complication of strabismus surgery. Among several risk factors, ASI occurs after strabismus surgery because of the nature of the anterior segment circulation. Disinsertion of rectus muscles leads to a decrease in the blood supply to the various anterior segment structures. We report a series of retrospective and prospective studies performed by our group focused on determining the risk of anterior segment ischemia following strabismus surgery, diagnosis, and modifications to surgical techniques to minimize the impact on anterior segment circulation. We found a significant decrease in postoperative anterior segment blood flow when operating vertical rectus muscles. Plication procedures preserve anterior segment circulation, and modifications to the technique allow the performance of adjustable sutures. Small adjustable selective procedures that spare the ciliary vessels have been demonstrated to be effective in patients with vertical and torsional diplopia. Ciliary sparing augmented adjustable transposition surgery decreases the risk of anterior segment ischemia while allowing management of potential post-operative alignment complications. Finally, ocular coherence tomography angiography is a valuable quantitative and qualitative technique to evaluate anterior segment ischemia. Strabismus surgeons should be aware of the risks of anterior segment ischemia when operating vertical rectus muscles. Modifications to standard surgical techniques allow surgeons to perform complex strabismus surgery in patients at risk for anterior segment ischemia.