Split-spectrum Amplitude-decorrelation Angiography Algorithm Research Articles

Glaucomatous Focal Perfusion Loss in the Macula Measured by Optical Coherence Tomographic Angiography

Purpose: To measure low perfusion area (LPA) and focal perfusion loss (FPL) in the macula using OCT angiography (OCTA) for glaucoma. DesignProspective, cross-sectional “case-control” comparison study. Methods: A total of 60 patients with primary open-angle glaucoma (POAG) and 37 normal participants were analyzed. AngioVue 6 × 6-mm high-definition (400 × 400 transverse pixels) macular OCTA scans were performed on one eye of each participant. Flow signal was calculated using the split-spectrum amplitude-decorrelation angiography algorithm. En face ganglion cell layer plexus (GCLP) and superficial vascular complex (SVC) images were generated. Using custom software, vessel density (VD) maps were obtained by computing the fraction of area occupied by flow pixels after low-pass filtering by local averaging 41 × 41 pixels. LPA was defined by local VD below 0.5 percentile over a contiguous area above 98.5 percentile of the normal reference population. The FPL was the percent VD loss (relative to normal mean) integrated over the LPA. Results: Among patients with POAG, 30 had perimetric and 30 had pre-perimetric glaucoma. The LPAGCLP-VD was 0.16±0.38 mm2 in normal and 5.78±6.30 mm2 in glaucoma subjects (P<0.001). The FPLGCLP-VD was 0.20%±0.47% in normal and 7.52%±8.84% in glaucoma subjects (P<0.001). The perimetric glaucoma diagnostic accuracy, measured by the area under the receiver operating curve, was 0.993 for LPAGCLP-VD and 0.990 for FPLGCLP-VD. The sensitivities were 96.7% and 93.3% at 95% specificity, respectively. The LPAGCLP-VD and FPLGCLP-VD had good repeatability (0.957 and 0.952 by intraclass correlation coefficient). Diagnostic accuracy was better than GCLP VD (AROC 0.950, sensitivity 83.3%) and OCT ganglion cell complex (GCC) thickness (AROC 0.927, sensitivity 80.0%), GCC focal loss volume (AROC 0.957, sensitivity 80.0%). The LPAGCLP-VD and FPLGCLP-VD correlated well with central VF mean deviations (Pearson's r=-0.716 and -0.705 respectively, both P<0.001). Conclusion: Assessment of macular focal perfusion loss using OCTA is useful in evaluating glaucomatous damage.

Contribution of systemic factors on macular vessel density: a sex-specific population-based study.

To evaluate the influence of systemic factors on macular vessel density in quantitative Optical Coherence Tomography Angiography (OCTA) by sex. A cross-sectional study. A total of 2018 adults were recruited in this study. Participants were excluded (n=964) due to missing data, eye-related problems, or low OCTA scan quality. Macular vessel densities were measured with OCTA using split-spectrum amplitude decorrelation angiography algorithm. Only the data from the right eyes were selected for analysis. Multivariable linear regression analysis was performed to determine the associations between macular vessel density and obesity-related systemic factors in each gender group. The right eyes of 1054 participants (59.6% women) were enrolled. Men had significantly higher obesity parameters and associated risk factors. In multivariable linear regression analysis in men, older age and type 2 diabetes mellitus were independently associated with lower superficial retinal vessel density (β = -0.37, p = 0.002; β = -1.22, p = 0.03) and deep retinal vessel density, respectively (β = -0.66, p < 0.001; β = -1.76, p = 0.02); positive association was also observed between body mass index (BMI) and superficial retinal vessel density (β = 0.56, p = 0.02). In women, only higher systolic blood pressure was independently associated with a lower deep retinal vessel density (β = -0.50, p = 0.003). This large cross-sectional study shows that older age and type 2 diabetes mellitus are associated with lower superficial and deep retinal capillary vessel density in men. This may help clinicians better understand how systemic factors influence retinal vessel density in different genders and future studies can ascertain more potential sex differences.

Light conditions influence optic nerve OCT angiography parameter in healthy subjects with neutral pupils

Optical coherence tomography angiography measurements are influenced by a range of environmental factors as blood pressure and physical fitness. The present study aimed to evaluate the effects of light and dark exposure in eyes with neutral and mydriatic pupils on vessel density in the macular and optic nerve head regions, as measured using optical coherence tomography angiography (OCTA). 55 eyes of 55 healthy volunteers (28 patients with neutral pupils; 27.18 ± 4.33 years) were examined using a high-speed and high-resolution spectral-domain OCT XR Avanti system with a split-spectrum amplitude de-correlation angiography algorithm. OCTA imaging was performed after dark adaptation and after exposure to light. The vessel density data of the superficial and deep retinal macular and optic nerve head region OCT-angiogram were analyzed for these two light conditions. Through Bonferroni correction for multiple testing, the p- value was adapted from 0.05 to 0.017. In eyes with neutral pupils, a significant increase was found in the capillary region of the optic nerve head region (p = 0.002), comparing dark- and light-adaptation. In the macular region of eyes with neutral (p = 0.718) and mydriatic pupils (p = 0.043), no significant differences were observed, as were any in the optic nerve head region of the mydriatic eyes (p = 0.797). This observation suggests that light conditions could be a possible factor influencing OCTA measurements. After dark exposure, vessel density data were significantly different between eyes with neutral and mydriatic pupils (nerve head region: p < 0.0001, superficial macula: p < 0.0001, deep macula: p = 0.0025). These data warn for the effect of mydriatic drops on vessel density measurements.

Paracentral acute middle maculopathy progressing to central retinal artery occlusion following coronavirus disease vaccination: a multimodal imaging report

Background: Coronavirus disease (COVID-19) vaccines can cause adverse ocular effects, including vascular insults, acute macular neuroretinopathy, paracentral acute middle maculopathy (PAMM), ophthalmic vein thrombosis, Graves’ disease, arteritic anterior ischemic optic neuropathy (A-AION), and nonarteritic AION. Here, we report a case of unilateral PAMM progressing to central retinal artery occlusion (CRAO) after COVID-19 vaccination, identified using multimodal imaging.&#x0D; Case Presentation: A 24-year-old healthy man presented with unilateral progressive blurring of vision in the right eye. He had a recent history of fever without rashes 2 weeks after coronavirus disease vaccination. He was diagnosed with PAMM in the right eye at a local hospital and treated with a tapering dose of oral steroids. At presentation, he showed progressive blurring of vision in the right eye and the best-corrected distance visual acuity (BCDVA) was 20/60. The anterior segment was normal. Fundus examination revealed a pale optic disc with arteriolar attenuation and barrage laser scarring at the inferotemporal periphery. CRAO was diagnosed based on the right eye findings. The patient underwent multimodal imaging, including wide-field fundus photography using Optos® (Optos Carfornia®, Optos Inc., Dunfermline, United Kingdom), multicolor imaging with Spectralis™ (Heidelberg Retinal Angiograph; Heidelberg Engineering, Inc., Dossenheim, Germany), fundus fluorescence angiography (Heidelberg Retinal Angiograph; Heidelberg Engineering, Inc., Dossenheim, Germany), and optical coherence tomography angiography (ANGIOVUE, OPTOVUE, Inc., Fremont, CA, USA) using the split-spectrum amplitude-decorrelation angiography algorithm. The condition progressed from PAMM to CRAO during the oral steroid treatment course. At the 2-month follow-up, the right eye BCDVA had improved to 20/50, with fundus findings remaining the same as at the previous visit.&#x0D; Conclusions: This was the first report of a young patient with PAMM presenting with focal vascular occlusion that evolved to global occlusion in the form of CRAO in the absence of systemic vascular risk factors and with a normal coagulation profile. This case suggests that arterial occlusion may exert a temporary effect secondary to COVISHIELD™ vaccination. Randomized controlled trials and case – control studies on the role of vaccination in precipitating thromboembolic events in healthy individuals would provide insight into the causation.

Peripapillary perfused capillary density in true versus pseudoexfoliation syndrome: An OCTA study.

PurposeTo compare peripapillary perfused capillary density (PCD) among eyes with true exfoliation syndrome (TEX), eyes with pseudoexfoliation syndrome (PEX), and healthy control eyes.Materials and methodsIn this observational cross-sectional study, eyes with and without TEX or PEX were assessed by optical coherence tomography angiography (OCTA) imaging. Bilateral OCTA images (4.5 × 4.5 mm2) centered at the optic nerve head were obtained using a commercial spectral domain OCTA system. Optic nerve head perfusion was quantified using the split-spectrum amplitude decorrelation angiography algorithm. Categorical and continuous variables were compared using the chi-squared test and one-way analysis of variance, respectively. The generalized estimating equation was used to adjust for confounding factors and determine inter-ocular associations.ResultsWe enrolled 39 eyes with TEX, 31 eyes with PEX, and 32 control eyes. There were no significant differences among the three groups regarding age, intraocular pressure, cup-to-disc ratio, blood pressure, or axial length (all p>0.05). There were significant differences in global PCD among the three groups (p = 0.01). There were significant differences in annular PCD between the TEX and PEX groups (p = 0.027).ConclusionsWhile both global and annular PCDs did not differ between the TEX and control groups, greater loss of annular PCD in the PEX group than in the TEX and control groups suggests more pronounced microvascular disturbance in PEX.Synopsis/PrecisGreater microvascular attenuation in PEX compared with TEX and normal control measured by OCTA.

Factors Affecting the Foveal Avascular Zone Area in Healthy Eyes among Young Chinese Adults.

Purpose To evaluate the influence of systemic and ocular factors on the foveal avascular zone (FAZ) area in young Chinese subjects' healthy eyes. Methods The current observational, cross-sectional study included 344 eyes from 172 healthy individuals (103 women, 69 men). Optical coherence tomography angiography realized with the split-spectrum amplitude-decorrelation angiography (SSADA) algorithm was used to assess the area of superficial FAZ. To determine the related factors and to reveal their potential correlations with the FAZ area, comprehensive examinations including both systemic and ocular ones were executed. Systemic examination involved factors including age, gender, and body mass index, while ocular examination involved factors including BCVA, refractive error, intraocular pressure, axial length (AL), anterior chamber depth, and central corneal thickness. Especially for fundus examination, central macular thickness (CMT), retinal volume, mean retinal thickness, macular blood flow area/vessel density in the superficial retinal layer (SRL) and deep retinal layer (DRL), mean retinal nerve fiber layer (RNFL) thickness, ganglion cell layer (GCL) thickness, C/D rate, rim area, and subfoveal choroid thickness were assessed, using mixed-effects regression models to appropriately account for intereye correlation. Subgroup analyses were performed based on gender and high myopia categories. Results The mean FAZ area was 0.30 ± 0.11 mm2 and varied significantly across gender (P = 0.0024). AL, CMT, and RNFL thickness were found significantly correlated with the FAZ area in the univariate regression analysis (AL, P = 0.0005; CMT, P < 0.0001; and RNFL thickness, P = 0.0461). According to the multivariate results, CMT and macular blood flow in SRL were negatively correlated with FAZ (CMT: P < 0.0001; macular blood flow in SRL: P = 0.00223). Mean retinal thickness, mean GCL thickness, and macular blood flow in DRL were positively correlated with FAZ (mean retinal thickness: P = 0.0005; mean GCL thickness: P < 0.0001; and macular blood flow in DRL: P = 0.0099). Correlation results among these filtered factors and FAZ were more pronounced in non-high-myopic eyes than in high-myopic eyes and had a significant difference when data of male and female subjects were processed separately from each other. Conclusion The present cross-sectional study performed comprehensive systemic and ocular examinations in young Chinese adults and filtered factors affecting FAZ. We indicated that among all the assessed candidate factors, gender, AL, retinal thickness, macular blood flow, RNFL, and GCL thickness affected the FAZ area most significantly. Such findings would facilitate future research concerning the role of FAZ variation in fundus diseases.

Macular Vessel Density Measured With Optical Coherence Tomography Angiography and Its Associations in a Large Population-Based Study

We investigate macular perfusion and the systemic and ocular associations in a population-based setting. In this cross-sectional study, 2018 adults residing in Hong Kong underwent detailed ophthalmic examinations after consenting to participate. Macular perfusion was measured with optical coherence tomography angiography (OCTA) using the split-spectrum amplitude decorrelation angiography algorithm. The parafoveal flow index and vessel area density were quantified using automated custom-built software. Of the 2018 participants, the OCTA measurements were available for 1940, and 1631 (84.1%) had good quality scans. The right eyes of these 1631 participants (43.1% men) were included for final analysis. Mean age was 49.8 years (range, 18-92 years). Mean global macular vessel density was 47.3% and 55.1% for the superficial and deep retinal layers, respectively. In multivariate analysis, lower superficial vessel density remained significantly associated with lower signal strength index (SSI; P < 0.001, standardized β = 0.607) and male sex (P < 0.001, β = 0.162), and borderline associated with older age (P = 0.09, β = -0.045) and longer axial length (AL; P = 0.09, β = -0.037), while lower deep layer vessel density was significantly associated with lower SSI (P < 0.001, standardized β = 0.667), longer AL (P < 0.001, β = -0.097), and higher creatinine (P < 0.001, β = -0.072). This large population-based study provided normative OCTA data of macular vessel density and demonstrated that a lower superficial retinal vessel density was significantly associated with lower SSI and male sex, while a lower deep layer retinal vessel density was significantly associated with lower SSI, longer AL, and higher level of creatinine. These associations must be considered when interpreting clinical quantitative OCTA data.

Immediate effects of smoking on optic nerve and macular perfusion measured by optical coherence tomography angiography

The aim of this study was the assessment of the relationship between cigarette smoking and optic nerve and macular vessel density measured by optical coherence tomography angiography. We examined 30 eyes from 30 healthy habitual smokers. The examination was performed using a high-speed and high-resolution spectral-domain optical coherence tomography RTVue XR Avanti with AngioVue (Optovue, Fremont, CA, USA) with a split-spectrum amplitude-decorrelation angiography algorithm. Blood pressure, heart rate, vascular density in the area of the optic nerve head (4.5*4.5 mm) and vascular density with the foveal avascular zone in the central macula (3.0*3.0 mm) were measured and analyzed before, immediately after and 30 minutes after cigarette smoking. Quantitative measurements were carried out by AngioAnalytics Phase 7 software. Immediately after smoking both heart rate and blood pressure increased significantly (p < 0.001) compared to values before smoking and then significantly decreased after 30 minutes comparing to values obtained right after smoking (p < 0.001). The mean area of the foveal avascular zone, parafoveal vessel density, and peripapillary vessel density did not change significantly. Our results show no immediate influence of smoking on vessel density parameters measured by specific OCTA machine in healthy habitual smokers.

Projection-Resolved Optical Coherence Tomographic Angiography of Retinal Plexuses in Retinitis Pigmentosa

To use projection-resolved optical coherence tomographic angiography (PR-OCTA) to characterize the microvascular changes in 3 distinct retinal plexuses in retinitis pigmentosa (RP) patients. Prospective cross-sectional study. A commercial 70-kHz spectral-domain optical coherence tomography (OCT) system was used to acquire 6-mm macular scans from RP patients and age-matched healthy participants at a tertiary academic center. Blood flow was detected using a commercial version of split-spectrum amplitude-decorrelation angiography (SSADA) algorithm. The PR-OCTA algorithm was used to suppress projection artifacts and resolve microvasculature in 3 plexuses around the macula. Vessel density was calculated from en face OCTA of the parafoveal and perifoveal regions in each of the 3 plexuses, as well as the all-plexus inner retinal slab. Inner and outer retinal thicknesses were measured form structural OCT scans. Generalized estimating equations and Spearman's rank correlation statistical methods were used. Forty-four eyes from 26 RP patients and 34 eyes from 26 healthy subjects were included. Significant reduction in vessel density was detected in the perifovea but not the parafovea of inner retinal slab of RP patients (P= .001 and P= .56, respectively) compared to controls. We also found deeper retinal plexuses (intermediate and deep capillary plexuses, ICP and DCP) were primarily damaged by RP, compared to superficial vascular complex (SVC). Significant thickening of the inner retina and thinning of the outer retina were also observed. Strong correlation was found between the vessel density in the perifoveal ICP and DCP and outer retinal thickness in RP patients with no history of cystoid macular edema. PR-OCTA enables the detection of microvascular changes in the perifoveal regions of the ICP and DCP in RP, with relative sparing of the SVC. OCT and OCTA parameters might be able to provide better understanding of the pathophysiology of the disease, as well as monitoring disease progression and the response to experimental treatments.

Decorrelation Signal of Diabetic Hyperreflective Foci on Optical Coherence Tomography Angiography

Diabetic hyperreflective foci in the outer retinal layers are a clinically relevant finding on optical coherence tomography (OCT) images, although their characteristics remain to be elucidated. Here we investigated the decorrelation signal around hyperreflective foci on OCT angiography (OCTA) images in diabetic retinopathy (DR). We retrospectively reviewed sufficient quality OCTA images from 102 eyes of 66 patients that were obtained using split-spectrum amplitude-decorrelation angiography algorithm. Most confluent hyperreflective foci were randomly deposited or appeared in a radiating array on the en-face structural OCT images in the inner nuclear layer (INL) or Henle’s fiber layer (HFL), respectively. Within the INL, hyperreflective foci were not accompanied by decorrelation signals and attached to capillaries on OCTA images. Decorrelation signals were sometimes delineated in hyperreflective foci in the HFL and other times appeared to be pseudopod-like or wrapping around hyperreflective foci, referred to as reflectance-decorrelated foci. The decorrelation signal intensity of hyperreflective foci in the HFL was associated with logMAR VA (R = 0.553, P < 0.001) and central subfield thickness (R = 0.408, P < 0.001) but not with DR severity. These data suggest that reflectance-decorrelated foci on OCTA images are clinically relevant as well as shed lights on the properties in diabetic hyperreflective foci.

Reduced Retinal Vessel Density in Primary Angle Closure Glaucoma: A Quantitative Study Using Optical Coherence Tomography Angiography.

The purpose of this article is to investigate the changes in the retinal vasculature in different parts of the fundus in eyes with primary angle closure glaucoma (PACG). Healthy subjects and those with PACG were enrolled. Optical coherence tomography and a split-spectrum amplitude decorrelation angiography algorithm were used to quantify the retinal vessel densities in the parafoveal and peripapillary areas. Thirty-nine eyes from 24 PACG patients and 39 eyes from 20 age-matched and sex-matched healthy subjects were included. The retinal vessel densities in the parafoveal and peripapillary areas and every sector of the 2 areas were significantly lower in the PACG eyes than in the healthy eyes. The difference was greater in the peripapillary area (11.75%) than in the parafoveal area (7.55%, P<0.05). In the PACG eyes, the vessel density in the peripapillary area correlated closely with the intraocular pressure, but that in the parafoveal area did not. When the PACG eyes were divided into groups with well-controlled and not well-controlled intraocular pressure (≤21 mm Hg or not), the vessel density and retinal nerve fiber layer thickness in the peripapillary area were much lower in the not well-controlled eyes (P<0.05), whereas the vessel density in the parafovea and the ganglion cell complex thickness were similar in the 2 subgroups. Retinal vessel density was significantly reduced in PACG eyes. The magnitude of this difference varied between the fundus areas, and was greater in the peripapillary area.

Changes in macular vasculature after uncomplicated phacoemulsification surgery: Optical coherence tomography angiography study

To use optical coherence tomography (OCT) angiography and a split-spectrum amplitude-decorrelation angiography algorithm to evaluate the changes in the macular vascular system after uncomplicated phacoemulsification. Department of Ophthalmology, Eye and and Ear, Nose, and Throat Hospital of Fudan University, Shanghai, China. Prospective case series. Patients with senile cataracts were included. Retinal vessel density and thickness at the macular area were checked by OCT at baseline and at 1week, 1month, and 3months after cataract surgery. Thirty-two eyes (32 patients) were included in the final analysis. There was a significant increase in retinal vessel density, a decrease in the foveal avascular zone at the macular area after the cataract surgery (all P<.05, repeated-measures analysis of variance), and an increase in full and inner macular thickness, all of which extended to the end of the follow-up period. At 3months postoperatively, there was a mean 6% and 3% increase in vessel density at the parafoveal and perifoveal regions, respectively, and a mean 27% reduction in the foveal avascular zone. The mean increase in inner retinal thickness was 15%, 10%, and 7% at the fovea, parafovea, and perifovea, respectively. Compared with the parafovea and perifovea, the fovea had a much higher percentage of change in retinal vasculature and inner retinal thickness (all P<.001). Macular vessel density and thickness increased after cataract surgery. Whether these changes will persist over a longer period still needs to be studied.

Changes in peripapillary blood vessel density in Graves’ orbitopathy after orbital decompression surgery as measured by optical coherence tomography angiography

ABSTRACTThe purpose is to evaluate the utility of optical coherence tomography (OCT) angiography in the evaluation of Graves’ orbitopathy (GO) and response to orbital decompression in patients with and without dysthyroid optic neuropathy (DON). This was a single-center, prospective case series in a cohort of 12 patients (24 orbits) with GO and ±DON, (6 orbits) who underwent bilateral orbital decompression. All patients underwent pre- and postoperative OCT angiography of the peripapillary area. Vessel density indices were calculated in a 4.5 mm × 4.5 mm ellipsoid centered on the optic disk using split-spectrum amplitude decorrelation angiography algorithm, producing the vessel density measurements. Mean change in vessel density indices was compared between pre- and postoperative sessions and between patients with and without DON. Patient 1, a 34-year-old male with GO and unilateral DON OD, showed a significant reduction in blood vessel density indices oculus dexter (OD) (DON eye) after decompression while a more modest reduction was found oculus sinister (OS) with the greatest change noted intrapapillary. Patient 2, a 50-year-old male with DON OU, showed worsening neuropathy following decompression OD that was confirmed by angiographic density indices. Patient 3, a 55-year-female with DON, showed a reduction in blood vessel density OD and increased density OS. Patients without DON showed overall less impressive changes in indices as compared to those with DON. Using OCT angiography, response to surgical treatment in GO orbits, more so in orbits with DON, can be demonstrated and quantified using vessel density indices with reproducibility.

Comparison of retinal microvascular changes in eyes with high-tension glaucoma or normal-tension glaucoma: a quantitative optic coherence tomography angiographic study.

The aim of this study is to determine and compare the changes in the retinal vasculature in eyes with high-tension glaucoma (HTG) or normal-tension glaucoma (NTG). The right eyes of 43 HTG subjects, 33 NTG subjects, and 51 age- and sex-matched normal subjects were included in this cross-sectional study. Signals were projected from the internal limiting membrane to retinal pigment epithelium. The retinal perfused vessel densities in the peripapillary and parafoveal regions were measured automatically with optic coherence tomography angiography and the split-spectrum amplitude-decorrelation angiography algorithm. Compared with normal eyes, glaucomatous eyes had a smaller retinal nerve fibre layer (RNFL) thickness, smaller full parafoveal retinal thickness, and lower retinal perfused vessel density (PVD) in the peripapillary and parafoveal regions (all P < 0.01). The visual field, RNFL and retinal thicknesses, and PVD in the parafoveal region in the HTG eyes were similar to those in the NTG eyes. However, the NTG eyes had a significantly lower mean PVD than the HTG eyes in the peripapillary region. When the different sectors of the peripapillary region were studied, the difference was still significant in most sectors (all P < 0.05), except the inferotemporal sector (P = 0.676). The retinal perfused vessel density is significantly reduced in HTG and NTG eyes, and more prominently in the peripapillary region in NTG eyes.

Findings of Optical Coherence Tomography Angiography in Best Vitelliform Macular Dystrophy

Purpose: To evaluate the vascular anatomy of eyes with Best vitelliform macular dystrophy (BVMD) using optical coherence tomography angiography (OCTA). Methods: This retrospective case-control study enrolled 11 consecutive BVMD patients and 13 age-matched healthy participants. Both eyes of each participant were imaged using a macular OCTA scan (3 × 3 mm) by 70-kHz 840-nm spectral-domain OCT. The flow signal was calculated using the split-spectrum amplitude-decorrelation angiography (SSADA) algorithm. Results: Qualitative analysis showed uneven hypo- and hyperintense signal changes at the choriocapillary level in OCTA images of BVMD patients. Quantitative analysis showed significant reductions in the flow density of the superficial vascular layer (whole: 49.2% vs. 53.9%, p < 0.001) and the choriocapillary flow area (5.1 vs. 5.5 mm², p = 0.02) in BVMD patients compared to controls. The choriocapillary flow area in the postvitelliform group was reduced compared to that of the vitelliform group. There was a statistically significant association between choriocapillary flow area and superficial vascular flow density (p = 0.045), choriocapillary flow area and foveal avascular zone area (p = 0.03). Conclusions: Vascular changes in BVMD were apparent in the choriocapillary layer. The changes became more striking in late stages of the disease. OCTA provides useful quantitative measurements for staging and monitoring the progression of BVMD.

Phenylephrine Affects Peripapillary Retinal Vasculature-an Optic Coherence Tomography Angiography Study.

Purpose: To evaluate and compare the effect of topical mydriatic eye drops (0.5% tropicamide alone, and a 0.5% tropicamide/0.5% phenylephrine mixture) on the retinal perfusion using optic coherence tomography angiography (OCTA).Methods: The perfused vessel density in the macular and peripapillary areas of both eyes was measured in eight healthy subjects using OCTA and a split-spectrum amplitude decorrelation angiography algorithm (SSADA). Various parameters, including retinal vessel density, were obtained at baseline and again 30 min after the instillation of either the tropicamide or the tropicamide/phenylephrine mixture eye drops in the right eye.Results: Following instillation of the tropicamide/phenylephrine mixture eye drops, there was a significant reduction of vessel density in the peripapillary area (from 89.63 ± 4.53% to 85.00 ± 4.14%, P = 0.034), but not in the macular areas. The mean effect size in the peripapillary area was −4.63%, and was not correlated with age, sex, or baseline vessel density. There was no reduction in vessel density in the macular or peripapillary areas after instillation of 0.5% tropicamide alone, and no reduction in vessel density in the contralateral (control) eyes.Conclusion: Topical phenylephrine reduced the retinal vessel density within the peripapillary area, but not within the macular area. Therefore, studies using OCTA, especially those focusing on the peripapillary area, should take into account this effect of phenylephrine on vessel density.

Wide-Field OCT Angiography Investigation of the Relationship Between Radial Peripapillary Capillary Plexus Density and Nerve Fiber Layer Thickness.

PurposeTo characterize the density and distribution of the radial peripapillary capillary plexus (RPCP) and its relationship with retinal nerve fiber layer (NFL) thickness in healthy subjects.MethodsUsing spectral-domain optical coherence tomography (OCT), split-spectrum amplitude decorrelation angiography algorithm and automated montaging, wide-field OCT angiography (OCTA) was used to measure the RPCP capillary density (CD) and NFL thickness. Polar sector-average CD and thickness maps were also created on each eye.ResultsWide-field OCTA (8 × 8 mm) in 10 healthy eyes from 10 subjects demonstrated the distribution of the RPCP throughout the posterior pole. RPCP-CD decreases with distance from the disc, but along the arcuate nerve fiber bundles relatively dense (> half maximum density) RPCP extends more than 5 mm from the disc and includes regions superior to and inferior to the macula. The RPCP-CD and NFL thickness are highly correlated (R2 = 0.85, P < 0.001) and fit well with a nonlinear stacked-layer model. The model fit suggests that the RPCP is present when the NFL is thicker than 17.9 μm and reaches a ceiling area density of 84% and that the RPCP has an apparent volume density of 19% at the current instrument transverse resolution. This indicates that capillary overlap can be expected to occur when NFL thickness reaches 40 μm.ConclusionsThe wide distribution of dense overlapping RPCP suggests that wider (up to 8 mm vertical and 7 mm horizontal) OCTA scans may be better investigate capillary loss in the early stages of glaucoma or other optic neuropathies.

SHORT-TERM EFFECTS OF EXERCISE ON OPTIC NERVE AND MACULAR PERFUSION MEASURED BY OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

To evaluate the effects of exercise on optic nerve and macular perfusion using optical coherence tomography angiography. Thirteen eyes of 13 healthy volunteers were examined using a high-speed and high-resolution spectral-domain optical coherence tomography XR Avanti with a split-spectrum amplitude-decorrelation angiography algorithm. Blood pressure, heart rate, the mean area of the foveal avascular zone , and flow density on the optic nerve head and macula, before and after exercise were measured and analyzed. Mean patient age was 27.3 ± 3.5 years. Heart rate, systolic and diastolic blood pressure increased significantly after exercise (P < 0.001). The mean area of the foveal avascular zone did not change significantly after exercise (before: 0.27 ± 0.07 mm; after: 0.26 ± 0.07 mm; P = 0.10). The peripapillary and the parafoveal flow density decreased significantly after exercise (peripapillary: before: 65.1 ± 2.1; after: 62.3 ± 3.0; P < 0.001 and parafoveal: before: 56.7 ± 1.3; after: 55.6 ± 1.5; P = 0.007). Increased physical activity induced significant changes in optic nerve and macular perfusion, which were measured using split-spectrum amplitude-decorrelation angiography optical coherence tomography angiography. In studies that aim to evaluate optic nerve and macular perfusion using optical coherence tomography angiography, it should be strongly recommended that patients rest before imaging is performed and that data concerning systemic circulation including blood pressure and pulse is included within the evaluation.

The Quantitative Measurements of Vascular Density and Flow Area of Optic Nerve Head Using Optical Coherence Tomography Angiography.

The purpose of this study was to evaluate the vascular density (VD) and the flow area on optic nerve head (ONH) and peripapillary area, and the impact of age and sex using optical coherence tomography angiography (OCTA) in healthy human subjects. Both eyes of each volunteer were scanned by an RTVue XR Avanti; Optovue with OCTA using the split-spectrum amplitude-decorrelation angiography algorithm technique. Masked graders evaluated enface angiodisc OCTA data. The flow area of ONH and the VD were automatically calculated. A total of 79 eyes of patients with a mean age of 37.03±11.27 were examined. The total ONH (papillary and peripapillary) area VD was 56.03%±4.55%. The flow area of the ONH was 1.74±0.10 mm/1.34 mm. The temporal and inferotemporal peripapillary VD was different between male and female patients. Increasing age causes some changes in the flow area of the ONH and the papillary VD from the third to the fourth decade (analysis of variance test; P<0.05). A normal quantitative database of the flow area and VD of the papillary and peripapillary area, obtained by RTVue XR with OCT angiography technique, is presented here.

OCT Angiography and Ellipsoid Zone Mapping of Macular Telangiectasia Type 2 From the AVATAR Study.

PurposeTo evaluate alterations on optical coherence tomography angiography (OCT-A) and quantitatively assess alterations in the ellipsoid zone (EZ) in eyes with macular telangiectasia type 2 (MacTel type 2).MethodsThe Observational Assessment of Visualizing and Analyzing Vessels With Optical Coherence Tomography Angiography in Retinal Diseases study is an institutional review board-approved prospective, observational study investigating OCT-A in macular disease. Patients underwent spectral-domain (SD)-OCT and OCT-A imaging at a single visit. SD-OCT data were analyzed using a novel OCT EZ-mapping software to obtain linear, area, and volumetric measurements of the EZ-retinal pigment epithelium (RPE) complex across the macular cube. OCT-A retinal capillary density was measured using the Optovue Avanti split-spectrum amplitude-decorrelation angiography algorithm. EZ-RPE parameters were compared to age-matched, sex-matched controls.ResultsFourteen eyes of seven patients (mean age, 59 ± 6.5 years) were analyzed. Mean visual acuity was 20/45 (range, 20/20–20/150). EZ-RPE central foveal mean thickness was 27.8 ± 6.7 μm, EZ-RPE central foveal thickness was 22.1 ± 21.6 μm, EZ-RPE central foveal area was 0.17 ± 0.04 mm2, and EZ-RPE central subfield volume was 0.017 ± 0.012 mm3. Each of these measurements was significantly inversely correlated with visual acuity (P < 0.02). In addition, all of these measurements were significantly reduced compared to controls (all P ≤ 0.005). OCT-A showed a reduced parafoveal vessel density of 50.8% temporally compared to 53.8% nasally (P = 0.01) in the superficial vascular plexus. In the deep vascular plexus, similar findings were noted with a parafoveal vessel density of 56.7% temporally and 58.8% nasally (P = 0.01).ConclusionsAbnormalities in EZ-RPE thickness, area, and volume are correlated with visual acuity in MacTel type 2, and may provide quantitative markers to measure disease progression and treatment response. OCT-A was a useful adjunct for determining disease severity.