Reproducibility of macular and optic nerve head vessel density measurements by swept-source optical coherence tomography angiography

Alterations in optical coherence tomography and optical coherence tomography angiography findings in children with partial biotinidase deficiency

OBJECTIVES

The aim of the study was to investigate whether retinal neurovascular structural impairment in children with partial biotinidase deficiency (BD) could be detected early via optical coherence tomography (OCT) and OCT angiography (OCTA).

METHODS

Eighty patients with partial BD and 80 control cases without any known systemic or ocular diseases were enrolled in this prospective study. Retinal neurovascular structures in the macular and optic disc regions were examined in using OCT and OCTA. Data from subjects with partial BD were compared with data from healthy controls.

RESULTS

A statistically significant decrease in the vessel density (VD) was observed in both superior and inferior parts of the superficial capillary plexus (SCP) and the deep capillary plexus (DCP) in the partial BD patient group compared with the control group (p<0.05). A significant decrease in the VD was also observed in the superior and inferior peripapillary SCP-DCP regions of the optic disc area in the patients with partial BD (p<0.05). Both the superficial and deep foveal avascular zone (FAZ) areas were significantly enlarged in the partial BD group with respect to the control group (p=0.026, p=0.021 respectively).

CONCLUSIONS

In the partial BD patients, the vascular density in the macula and optic disc region is decreased in childhood, when compared to the control group. In patients with partial BD, it would be very useful to detect the early neurovascular changes that may occur during the course of the disease by means of a noninvasive technique such as OCTA.

Repeatability of swept-source optical coherence tomography angiography automated macular vessel density

INTRODUCTION

Optical Coherence Tomography Angiography Ratio Analysis (OCTARA) is capable of visualizing inner and outer retinal vascular plexuses, choriocapillaris, and larger choroidal vasculature in vivo without contrast injection. The aim of this study was to assess the intrasession repeatability of automated vessel density measurements using Triton Swept-Source Optical Coherence Tomography Angiography (OCTA) innovative algorithm OCTARA in retinal and choroidal vasculature.

METHODS

To study population between 65-90 years old with no eye diseases. For each subject measurements were performed four times. The intraclass correlation coefficient and the coefficient of variation were calculated to analyze repeatability of the OCTARA automatically generated vessel density measurements.

RESULTS

A total of 35 eyes were included in the study. The intraclass correlation coefficient of the global vessel density in the superficial capillary plexus and the deep capillary plexus were 0.963 and 0.975, respectively, and the coefficient of variation were 5.4% and 4.4%, respectively. The intraclass correlation coefficient of the rest of the global measurements was indicative of good reliability with the exception of the deep choroid layer with an intraclass correlation coefficient of 0.6 indicative of moderate reliability.

CONCLUSIONS

Our results proved excellent repeatability of automated vessel density measurements in the superficial and deep capillary plexus layers in our cohort using a OCTARA algorithm indicating that it may be a reliable diagnostic tool. It also showed good reliability in choriocapillary and mid choroid layer. These findings may be of value in assessing the significance of differences in capillary density measurements over time and across different settings.

VEGFA may be a potential marker of myopic choroidal thickness and vascular density changes

To evaluate the changes of choroidal thickness (CT) and blood flow related to myopia, and its effects of vascular endothelial growth factor (VEGFA) on choroidal vessels in myopia. Subjects were included and divided into emmetropia (EM), non-high myopia (Non-HM) and high myopia (HM) groups. we measured choroidal thickness (CT), choriocapillaris vessel density (VD), and VEGFA content in tears in humans (137 subjects for CT, VD and 84 for tear) and detected the role of VEGFA in the choroid in form-deprivation myopia (FDM) in guinea pigs. Twenty-four guinea pigs were divided into control and FDM groups, and the expression changes of choroidal vessels and VEGFA were observed and compared using immunohistochemistry and Western blotting. Twenty-one guinea pigs were divided into control, FDM + Vehicle and FDM + Conbercept groups. The changes of diopter, axis length and choroidal vessels after intravitreal injection of Conbercept were observed. There were significant differences in CT and VD among the three groups (p < 0.05). VEGFA levels in tears were significantly lower in the myopic groups, with a decreasing trend from EM to Non-HM to HM. The choroidal vascular area fraction of FDM decreased compared to the control group. FDM guinea pigs exhibited reduced choroidal vasculature and significant downregulation of VEGFA expression. Following intravitreal injection of conbercept, the FDM + Conbercept group showed greater myopia, longer axial length, and lower choroidal vascular area fraction compared to the control group. VEGFA may participate in the regulation of choroidal blood vessels and blood flow in the progression of myopia. The reduction in VEGFA may accelerates the progression of myopia.

Repeatability of retinal and choroidal optical coherence tomography angiography indices in healthy children and young adults

PURPOSE

To evaluate the repeatability of retinal and choroidal optical coherence tomography angiography (OCT-A) indices among healthy children and compare it to healthy young adults.

METHODS

This prospective study captured 3 mm × 3 mm and 6 mm × 6 mm macular OCT-A scans including superficial and deep retinal layers, choriocapillaris and deep choroid over two visits, 1 week apart at approximately the same time of day, for 22 healthy adults (18-30 years) and 21 children (6-15 years). Magnification and projection-artefact corrected indices extracted using a custom image analysis program and individual biometry were compared between visits using Bland-Altman analysis and intraclass correlation (ICC). Retinal indices included foveal avascular zone metrics, perfusion and vessel density and choroidal indices included choriocapillaris flow deficit metrics and deep choroid perfusion density, in the foveal, parafoveal and perifoveal regions. Repeatability between adults and children was compared with F-test.

RESULTS

Bland-Altman analysis showed that the mean differences between repeated OCT-A indices were not significantly different from zero for either of the zones, layers and scan sizes in the two age groups (p > 0.05) except for foveal vessel density and foveal avascular zone perimeter (p = 0.04 for both) of 6-mm-deep retinal layer scans. The ICC ranged between 0.67 and 0.99. Significantly higher variability between visits (p < 0.05) in the indices was noted among adults than children, especially for choroidal indices of larger scan size.

CONCLUSION

The retinal and choroidal OCT-A indices in the foveal, parafoveal and perifoveal zones were repeatable in healthy children except for the foveal vessel density and foveal avascular zone perimeter of the 6-mm-deep retinal layer, which exhibited statistically borderline differences between visits. The adult group showed more variability between visits compared to children, especially in the larger scan size for choroidal OCT-A indices.

Optical coherence tomography angiography in diabetic retinopathy: A major review

Diabetic retinopathy (DR) is characterized by retinal vasculopathy and is a leading cause of visual impairment. Optical coherence tomography angiography (OCTA) is an innovative imaging technology that can detect various pathologies and quantifiable changes in retinal microvasculature. We briefly describe its functional principles and advantages over fluorescein angiography and perform a comprehensive review on its clinical applications in the screening or management of people with prediabetes, diabetes without clinical retinopathy (NDR), nonproliferative DR (NPDR), proliferative DR (PDR), and diabetic macular edema (DME). OCTA reveals early microvascular alterations in prediabetic and NDR eyes, which may coexist with sub-clinical neuroretinal dysfunction. Its applications in NPDR include measuring ischemia, detecting retinal neovascularization, and timing of early treatment through predicting the risk of retinopathy worsening or development of DME. In PDR, OCTA helps characterize the flow within neovascular complexes and evaluate their progression or regression in response to treatment. In eyes with DME, OCTA perfusion parameters may be of predictive value regarding the visual and anatomical gains associated with treatment. We further discussed the limitations of OCTA and the benefits of its incorporation into an updated DR severity scale.

Reduced Retinal Blood Vessel Densities Measured by Optical Coherence Tomography Angiography in Keratoconus Patients Are Negatively Correlated with Keratoconus Severity

Keratoconus (KC) is the most common corneal ectasia. Optical coherence tomography angiography (OCT-A) is a relatively new non-invasive imaging technique that allows the visualization and quantification of retinal and choriocapillary blood vessels. The aim of this study is to assess retinal and choriocapillary vessel density (VD) differences between KC patients and healthy controls and to investigate correlations between VD and KC severity. Fifty-two eyes were included in this exploratory study: twenty-six eyes from 26 KC patients and twenty-six eyes from 26 age- and gender-matched healthy controls. All patients underwent Scheimpflug corneal topography with Pentacam, axis lengths measurement and optical coherence tomography angiography (OCT-A). The thinnest spot in corneal pachymetry, maximum K (Kmax) and KC severity indices from the Belin/Ambrósio enhanced ectasia display (BAD) were also assessed. There was a distinct reduction particularly in the retinal VD of the superficial capillary plexus (SCP). Correlation analyses showed strong and moderate negative correlations between the VD in the macular SCP and BAD KC scores and between the SCP VD and Kmax. There was no difference in retinal thickness between the KC and healthy controls. With this study, further evidence for altered VD measurements by OCT-A in KC patients is given. For the first time, we demonstrated negative correlations between BAD KC scores and retinal blood vessel alterations. A major limitation of the study is the relatively small sample size. Since an artefactual reduction of the quantitative OCT-A measurements due to irregular corneal topography in KC must be assumed, it remains to be investigated whether there are also actual changes in the retinal microcirculation in KC.

Quantitative Analysis of the Choroidal Vascularity in Eyes with Uveitis Using Optical Coherence Tomography Angiography: A Systematic Review

PURPOSE

The purpose of this systematic review is to identify techniques used for quantification of choriocapillaris (CC) flow in eyes with uveitis using optical coherence tomography angiography (OCTA), report reliability and level of correlation with techniques such as indocyanine green angiography (ICGA).

METHODS

A systematic search of several databases was done. The studies were analyzed for techniques of measurement, reliability, and correlation with other modalities. Risk of bias assessment was performed.

RESULTS

Thirteen studies were included. CC vessel density (7 studies) and flow deficit area (4 studies) were the most used indices. There was significant heterogeneity in the studies due to differences in the scan protocol, thresholding strategy, and analysis. Comparison with ICGA was performed by only one study, and reliability indices were reported by only two studies.

CONCLUSION

OCTA is a useful tool to measure the CC vascularity in eyes with uveitis. However, standardized acquisition and analysis protocols are needed.

Reproducibility of peripapillary, optic nerve head and macular vessel density by OCT-A according to glaucoma severity staging

OBJECTIVE

To assess the reproducibility of peripapillary, optic nerve head (ONH-PP) and macular vessel density (VD) by Spectral Domain optical coherence tomography angiography (SD OCT-A) in glaucoma patients and healthy subjects.

METHODS

Cross-sectional study assessing 63 eyes of 63 subjects, including 33 glaucoma patients and 30 healthy subjects. Glaucoma was classified in mild, moderate, or advanced. Two consecutive scans were acquired by Spectralis Module OCT-A (Heidelberg, Germany), and provided images of the superficial vascular complex (SVC), nerve fiber layer vascular plexus (NFLVP), superficial vascular plexus (SVP); deep vascular complex (DVC), intermediate capillary plexus (ICP) and deep capillary plexus (DCP). VD (%) was calculated by AngioTool. Intraclass correlation coefficients (ICCs) and coefficients of variation (CV) were calculated.

RESULTS

Among ONH-PP VD, better ICC presented advanced (0.83-0.97) and moderate glaucoma (0.86-0.96) compared with mild glaucoma (0.64-0.86). For the macular VD reproducibility, ICC results for superficial retinal layers were better for mild glaucoma (0.94-0.96) followed by moderated (0.88-0.93) and advanced glaucoma (0.85-0.91), and for deeper retinal layers ICC was better for moderate glaucoma (0.96-0.95) followed by advanced (0.80-0.86) and mild glaucoma (0.74-0.91). CVs ranged from 2.2%% to 10.94%. Among healthy subjects, ICCs for the ONH-PP VD measurements (0.91-0.99) and for the macular VD measurements (0.93-0.97) were excellent in all layers, with CVs from 1.65% to 10.33%.

CONCLUSIONS

SD OCT-A used to quantify macular and ONH-PP VD showed excellent and good reproducibility in most layers of the retina, both in healthy subjects and in glaucoma patients regardless of the severity of the disease.

Association between macular and papillary vessel density by optical coherence tomography angiography in a large healthy population

PURPOSE

To provide a normative data set of the relationship between macular and papillary vessel density (VD) using swept-source optical coherence tomography angiography (SS-OCTA) in a large healthy population.

METHODS

Cross-sectional study conducted on 346 right eyes of healthy subjects. Macular and papillary SS-OCTA VD measurements of the retinal superficial capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillaris (CC) in the central area and the four quadrants were obtained. Correlations between macular and papillary VD among different quadrants were assessed.

RESULTS

The mean participant age was 37.7 ± 19.8 years (range 5-83); 59% were women. No correlation was detected neither for the global SCP (R = 0.050; P = 0.040), DCP (R = -0.056; P = 0.038) nor CC (R = 0.102; P < 0.001) between macular and papillary VD. In a subanalysis, there was also no correlation in any of the quadrants studied (R ≤ 0.180; P < 0.001). In a subgroup of 45 left eyes, there was no correlation in the different plexus and layers studied between macular and papillary vasculature. No differences in SCP, DCP and CC were found according to gender, age or axial length in the relationship between macular and papillary VD.

CONCLUSION

There is no association between macular and papillary VD neither in the SCP, DCP or CC in any of the regions studied. Hence, macular and optic nerve head vascularization should be investigated separately to identify which structure is more relevant in each disease.

Repeatability of choriocapillaris flow voids by optical coherence tomography angiography in central serous chorioretinopathy

PURPOSE

To assess the repeatability of flow signal voids (FSV) measurements of the choriocapillaris (CC) and choroid (CH) in central serous chorioretinopathy (CSCR) by Swept-Source optical coherence tomography angiography (SS-OCTA).

METHODS

Cross-sectional study including 104 eyes of 52 patients with unilateral CSCR. Two consecutive macular 6x6 mm SS-OCTA scans (Plex Elite 9000; Zeiss, Dublin, CA) were obtained from the affected eyes with persistent subretinal fluid (SRF) (CSCR group) and the fellow unaffected eyes (control group). FSV area and the number of contours measurements were analyzed using three slabs: inner CC, outer CC and CH. The repeatability of the measurements was assessed with intraclass correlation coefficients (ICC) and coefficients of variation (CV).

RESULTS

In the CSCR group, ICCs for the FSV area in the three slabs were all ≥0.859, observing higher values for the outer CC and the CH (0.959 and 0.964) than for the inner CC (0.859). Similar ICC values were obtained for the FSV area in control eyes, observing the highest values for the outer CC (0.949), followed by the CH (0.932) and inner CC (0.844). Regarding the FSV number of contours measurements, ICCs were higher for the outer CC and CH (0.949 and 0.932) than for inner CC (0.844). CV for the FSV area was 4.7%, 3.8% and 8.6% in the CSCR eyes and 4.8%, 3.9% and 9.3% in the control group for the inner CC, outer CC and CH respectively.

CONCLUSION

SS-OCTA offers good repeatability to quantify macular FSV in CSCR eyes and fellow eyes.

Correlation between radial peripapillary vascular density and reduced central corneal thickness in glaucoma suspect patients

Background

Optical coherence tomography (OCT) angiography (OCTA) provides a quantitative assessment of the microcirculation of the retina and choroid. It may precede the retinal nerve layer (RNFL) and optic disc head defects. Retinal nerve fiber layer defects and reduced central corneal thickness (CCT) are important parameters in the assessment of a glaucoma suspect patients. The aim of this study is to investigate any possible relationship between the reduced central corneal thickness and the radial peripapillary capillary (RPC) density defect in glaucoma suspect.

Methods

In this cross sectional study, 92 eyes were incorporated. Peripapillary OCT angiography (4.5 mm) and Anterior segment OCT for corneal pachymetry were done. C/D Ratio, thickness of nerve fiber layer, the blood flow indices and central corneal thickness also were evaluated.

Results

In eyes of glaucoma suspect patients; a significant positive correlation between CCT and total RPC density was detected (r = 0.38, P < 0.001). A strong positive correlation was also found between total RPC and peripapillary RNFL thickness (r = 0.55, P < 0.001).

Conclusion

Reduced central corneal thickness and peripapillary capillary density are two screening parameters for glaucoma suspect patients. The radial peripapillary capillary density is a valid diagnostic tool for glaucoma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02628-z.

Normative Data and Determinants of Macular, Disc, and Peripapillary Vascular Density in Healthy Myopic Children Using Optical Coherence Tomography Angiography

Objective

To establish a normative database for the vascular density (VD) in macular, disc, and peripapillary regions in healthy myopic children and to evaluate associated ocular features with optical coherence tomography angiography (OCTA).

Methods

This was an observational, prospective and cross-sectional study. 776 Chinese healthy myopic children (375 boys and 401 girls) were enrolled, mean (±SD) age 9.84 ± 1.98 (range 6–16) years. En-face angiogram OCTA was performed on 6 mm × 6 mm retinal and 4.5 mm × 4.5 mm disc regions. VD measurements in the macular retina were segmented into the four regions: superficial capillary plexus (SCP), intermediate capillary plexus (ICP), deep capillary plexus (DCP), and choriocapillaris (CC). Correlations between macular, disc, and peripapillary VD and possible influencing factors [age, gender, axial length (AL), spherical equivalent refraction (SER), right/left eye, and signal strength index (SSI)] were assessed by Pearson’s correlation and multivariate regression analysis.

Results

For macular scans, the corrected VD in the ICP region was (48.25 ± 4.24)% for the whole macular retina. The macular ICP VD in most sections was lower than the SCP, DCP, and CC (all P < 0.001). The corrected VD in CC was (72.96 ± 4.42)% for the whole macular retina. The macular CC VD in every section was all higher than the SCP, ICP, and DCP (all P < 0.001). The size of foveal avascular zone (FAZ) and foveal VD 300 (FD-300) was 0.28 mm²± 0.10 mm² and (58.43 ± 4.17)% respectively. For disc scans, the corrected VD was (58.04 ± 2.73)% for the whole disc area. Both AL and SER were strongly correlated with ICP, DCP, and CC VD in all regions (all P < 0.01). Larger SSI was correlated with a lower VD in the SCP and ICP, and a higher VD in DCP and CC (all P < 0.01).

Conclusion

Vascular density values provide large scale normative data on macular, disc, and peripapillary vascular parameters in a large sample of healthy myopic children with OCTA measured in the four different retinal plexuses and regions. The VD in different regions had various influencing factors; mainly a close correlation with AL and SSI.

Attenuated Amplitude of Pattern Electroretinogram in Glaucoma Patients with Choroidal Parapapillary Microvasculature Dropout

This study aims to investigate whether parapapillary choroidal microvasculature dropout (MvD) is related to visual function measured by pattern electroretinogram (PERG) in glaucomatous eyes with β-zone parapapillary atrophy (PPA). A total of 79 patients with open angle glaucoma and preperimetric glaucoma with β-zone PPA was included in this cross-sectional study. Through the deep layer of the Swept-source optical coherence tomography angiography image, the angular width and the area of MvD were measured. Visual function was evaluated with a standard automated perimetry and PERG. N95 and P50 PERG amplitudes in eyes with MvD were noticeably decreased compared to those without MvD (p = 0.004 and p = 0.007, respectively), although the mean deviation was not significantly different (p = 0.107). The lower N95 amplitude was associated with the presence of MvD (β = −0.668, p = 0.017) and wider angular width of MvD (B = −7.612, p = 0.014). Old age (p = 0.001), average ganglion cell’s inner plexiform layer thickness (p = 0.003), and the presence of MvD (p = 0.020) were significantly related to low N95 amplitude. Association between the presence and extent of the MvD and PERG amplitudes suggests that the presence of MvD has relevance to the generalized dysfunction of retinal ganglion cells.

The Impact of Superficial Vessel Density on Glaucoma Progression according to the Stage of Glaucoma

Purpose: To investigate the clinical significance of vessel density (VD) on visual field (VF) progression regarding the severity of glaucoma. Methods: A total of 130 eyes were recruited in this retrospective and longitudinal study. Superficial and deep VDs in circumpapillary and macular regions were measured via ImageJ. The rate of VF progression was defined as the mean deviation (MD) slope (dB/year). Linear regression was used to verify factors affecting deterioration of VF. The eyes with lower superficial VD were further analyzed. Results: Fifty patients with early glaucoma (EG) (MD > −6 dB) and 52 patients with moderate-to-advanced glaucoma (MAG) (MD ≤ −6 dB) were included. A faster progression rate was found in MAG (p = 0.049). Superficial VD was noticeably related to the VF progression rate in total eyes and in MAG (Both Ps ≤ 0.007, respectively). With patients in the lower half of the superficial VD, the VD was significantly associated with the rate of progression (B, 0.049, p = 0.021). This association was independent of the baseline MD and OCT parameters. Conclusion: Decreased superficial VD might conversely affect the progression of glaucoma even in MAG, which suggests superficial VD could be used as a potential marker to foresee the disease progression even in progressed eyes.

Peripapillary Microvascularization Analysis Using Swept-Source Optical Coherence Tomography Angiography in Optic Chiasmal Compression

Purpose

To evaluate the vessel density (VD) of the radial peripapillary capillary (RPC) network using swept-source optical coherence tomography angiography (SS-OCTA) “en face” images of eyes with chiasmal compression caused by brain tumors before and after decompressive surgery compared with healthy controls.

Methods

A cross-sectional study was conducted in 12 patients with chiasmal compression confirmed by neuroimaging. Sixteen healthy participants were also included. All patients with chiasmal compression underwent a neuro-ophthalmological examination one week before and 6 months after brain surgery, including static automated perimetry as well as measurement of the thickness of the retinal nerve fiber layer (RNFL) and the ganglion cell complex (GCC) with spectral-domain optical coherence tomography (SD-OCT). Based on this neuro-ophthalmological examination, the presence of an optic neuropathy (ON) was evaluated. Peripapillary VD was obtained in four sectors on a 6 × 6 mm SS-OCTA image using the Cirrus Plex Elite 9000.

Results

Baseline average VD was significantly lower in patients with chiasmal compression and ON than in controls (median: 55.62; interquartile range (IQR): 2.96 vs. 58.53; IQR: 2.02; p=0.003). This decrease was also found in the temporal, superior, and nasal sectors. Average postoperative VD was decreased in patients with chiasmal compression compared with average preoperative VD (median: 56.16; IQR: 4.07 vs. 57.48; IQR: 3.83; p=0.004). Preoperative VD was significantly correlated with RNFL, GCC thickness, and visual field defects.

Conclusions

The VD of the RPC network was decreased in chiasmal compressive ON, and it was further decreased at 6 months after decompressive surgery.

Determinants of vessel defects in superficial and deep vascular layers in normal-tension glaucoma using optical coherence tomography angiography

We investigated the characteristics of localized vessel density defects (VD) either in the deep or superficial vascular layer of normal-tension glaucoma patients using optical coherence tomography angiography (OCTA). In this retrospective, cross-sectional study, 74 eyes with localized retinal nerve fiber layer (RNFL) defect were included. The relationships between the widths of the VD in the superficial and deep layer and ocular factors were evaluated. Eyes with greater deep VD were significantly older (P = 0.023). The IOP measured at OCTA exam was significantly related to the width of the deep VD (P = 0.009). By contrast, average ganglion cell inner plexiform layer thickness (GCIPLT) was substantially related to the width of the superficial VD (P = 0.004). In logistic regression analysis, aging was noticeably associated with wider deep VD, whereas worse mean deviation (MD) had a significant association with wider superficial VD (P = 0.001, P = 0.003, respectively). In sum, while changes of the superficial layer seemed an overall ramification of glaucomatous damages, the deep layer was more likely to be affected by factors related to ocular microcirculation, such as IOPs and older age. Thus, looking into the deep vascular layer using OCTA could identify risk factors related to the disturbance in ocular microcirculation.

Repeatability of Macular and Optic Nerve Head Measurements by Optical Coherence Tomography Angiography in Healthy Children

Aims: To evaluate the repeatability of the peripapillary and macular vascular parameters using optical coherence tomography angiography (OCT-A) in healthy children.Materials and methods: Cross-sectional study including 34 eyes of 34 healthy children. After a complete medical examination, two consecutive OCT-A exams were done using AngioPlex Cirrus 5000 (Carl Zeiss Meditec, Dublin, CA, USA) in the same session. The scan area used was 6 × 6 mm for the analysis of the superficial vascular plexus (SVP) in the macula, and 4.5 × 4.5 mm for the peripapillary plexus. To study the repeatability of the measurements, the intraclass correlation coefficient (ICC) and the coefficient of variation (CV) of each pair of exams were calculated.Results: The mean age of the children included was 10.77 ± 2.49 years (range 6 to 15 years). Good and excellent ICCs were obtained for all the parameters considered. Peripapillary vascular parameters showed greater reproducibility than macular ones (global peripapillary perfusion density (pPD): ICC = 0.834 CV = 0.89% vs. whole macular area PD (w-mPD): ICC = 0.697 CV = 3.49%; global peripapillary flux index (FI): ICC = 0.858 CV = 1.28%; whole macular area vascular density (VD): ICC = 0.699 CV = 3.30%). Amongst the macular parameters, the characteristics of the foveal avascular zone (FAZ) were the ones showing higher rates of repeatability (FAZ circularity: ICC = 0.858 CV = 8.83%).Conclusion: OCT-A is a non-invasive, time-efficient technology that may be useful in the evaluation of the retinal and peripapillary vascular network in healthy children. The repeatability of the measures will allow the follow-up and evaluation of any change occurring in the macular or optic nerve perfusion.

Quantitative assessment and determinants of the papillary microvasculature in healthy subjects

BACKGROUND

It is critical to monitor the optic disc's vessel density using Optical coherence tomography angiography (OCTA) and evaluate its determinants. In the current study, we investigate the superficial vessel density (VD) of the papillary microvasculature and its determinants in healthy subjects of Southern China.

METHODS

This was a prospective, cross-sectional study. Superficial VD in healthy individuals' optic disc region was measured by OCTA. The factors associated with ocular and systemic parameters were analyzed using a generalized estimation equation (GEE) model.

RESULTS

A total of 510 eyes of 260 healthy subjects were analyzed in the study. The total VD in the optic disc area was 17.21 ± 2.15 mm- 1 (95% CI, 17.02-17.40 mm- 1). The VD in the inner ring and the outer ring of the optic disc were significantly higher compared with the central ring, while the VD of the superior quadrant and inferior quadrant was significantly higher compared with the temporal and nasal quadrant. After adjusting for the ocular factors and systemic factors, AL (β = - 0.4917, P = 0.0003), disc area (β = - 0.3748, P = 0.0143), CMT (β = - 0.0183, P = 0.0003) and SSI (β = 1.0588, P < 0.001) were significantly associated with total VD of the optic disc.

CONCLUSION

The mean total VD in the optic disc area was 17.21 ± 2.15 mm- 1 in healthy subjects, and the superior and inferior VD was significantly higher than the temporal and nasal VD. AL, disc area, CMT, and SSI may affect the total VD in the optic disc area and should be considered in clinical practice.

Retinal applications of swept source optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA)

The advent of optical coherence tomography (OCT) revolutionized both clinical assessment and research of vitreoretinal conditions. Since then, extraordinary advances have been made in this imaging technology, including the relatively recent development of swept-source OCT (SS-OCT). SS-OCT enables a fast scan rate and utilizes a tunable swept laser, thus enabling the incorporation of longer wavelengths than conventional spectral-domain devices. These features enable imaging of larger areas with reduced motion artifact, and a better visualization of the choroidal vasculature, respectively. Building on the principles of OCT, swept-source OCT has also been applied to OCT angiography (SS-OCTA), thus enabling a non-invasive in depth-resolved imaging of the retinal and choroidal microvasculature. Despite their advantages, the widespread use of SS-OCT and SS-OCTA remains relatively limited. In this review, we summarize the technical details, advantages and limitations of SS-OCT and SS-OCTA, with a particular emphasis on their relevance for the study of retinal conditions. Additionally, we comprehensively review relevant studies performed to date to the study of retinal health and disease, and highlight current gaps in knowledge and opportunities to take advantage of swept source technology to improve our current understanding of many medical and surgical chorioretinal conditions. We anticipate that SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift to more widespread adoption of new imaging technology to clinical practice.

Effects of physical exercise on macular vessel density and choroidal thickness in children

We used swept-source (SS) optical coherence tomography (OCT) and OCT angiography (OCTA) to investigate the effects of moderate physical exercise on retinal and choroidal vessel densities (VDs) and thicknesses in children. One eye in each of 40 myopic children (mean age, 11.70 years) and 18 emmetropic children (mean age, 11.06 years) were included. SS-OCT 6 × 6-mm radial scans and SS-OCTA 3 × 3-mm images were centered on the macula. Heart rate (HR), systolic and diastolic blood pressure, and intraocular pressure (IOP) were recorded before and immediately after a 20-min stationary cycling exercise and after a 30-min rest. The subfoveal choroidal thickness (SFCT), choroidal thickness (CT), and VD at the superficial and deep retinal layers, choriocapillaris, and deeper choroidal vessels were determined. SFCT and CT were significantly lower at all locations immediately after exercise (p < 0.001) and did not fully recover after rest (p < 0.05). VD was lower in the deep retinal layer after exercise (p = 0.02) and higher in the superficial layer after rest (p = 0.03) in myopic eyes while it was higher in the superficial (p < 0.01) and deep layer (p < 0.01) after rest in emmetropic eyes. No significant exercise-related changes in the superficial retinal VD, choroidal VD, or IOP were observed. ΔCT% and ΔSFCT% were significantly correlated with increases in HR in myopic group (p = 0.04 and p = 0.03, respectively). Exercise increased retinal VD after rest in emmetropic eyes, and caused significant CT thinning that lasted for at least 30 min in both emmetropic and myopic eyes.

Microvascular alterations in children with optic disk drusen evaluated by optical coherence tomography angiography

PURPOSE

To asses changes in vessel density (VD) in children with optic disk drusen (ODD) using swept source optical coherence tomography angiography (OCTA).

METHODS

Cross-sectional study of 27 eyes with ODD compared with age-matched controls. Peripapillary and macular VD were measured in the superficial retinal capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillaris (CC). The correlation between VD changes with alterations in retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), and visual field (VF) was analyzed.

RESULTS

Mean participant age was 12.5 ± 3.3 years (range, 7-18 years); 63% was females. In the patients vs. controls, median central peripapillary VD was 52.9% vs. 50.6% (p = 0.63) for SCP; 48.1% vs. 53.8% (p = 0.017) for DCP; and 17.0% vs. 28.2% (p = 0.0037) for CC, respectively. VD in the superior and nasal CC layers was significantly lower in the patients (36.3% vs. 56.2%; p < 0.001) and (60.4% vs. 70.3%, p < 0.001), respectively. No significant differences were observed for VD in the macular region. The RNFL was thinner in eyes with superficial drusen versus controls (87 vs. 111 μm; p < 0.001). No significant differences between were observed in GCL thickness (p = 0.13). Nasal SCP and nasal RNFL VD were moderately correlated (r = 0.54, p < 0.01), while mean VF deviation was strongly correlated with median SCP VD in patients with superficial drusen (r = 0.9, p = 0.03).

CONCLUSION

Impaired VD was observed in the peripapillary nasal CC in patients with ODD; this impairment was associated with a decreased RNFL thickness. Nasal SCP VD and RNFL thickness were moderately correlated in patients with ODD.

Evaluation of the different thresholding strategies for quantifying choriocapillaris using optical coherence tomography angiography

BACKGROUND

In this paper, we evaluate the different thresholding strategies that have been used for the quantification of the choriocapillaris (CC) and explore their repeatability and the interchangeability of the measurements resulting from its application.

METHODS

Observational study. Eighteen eyes from nine healthy volunteers aged >18 years were imaged four consecutive times with a SD-OCTA system (Heidelberg Engineering, Germany) using a 10°×10° high-resolution protocol centered on the fovea. Projection artifacts were removed, and the CC was bracketed between 10 and 30 µm below Bruch's membrane. For the quantification of CC, we used four flow deficits (FD) parameters: FD number, mean FD size, total FD area and FD density. We performed a systematic review of literature to collect the thresholding methods that have been used for the quantification of CC. The CC quantification parameters were then evaluated after applying each of the thresholding strategies. Intraclass correlation coefficient (ICC) and Pearson's correlation analysis were used to compare the repeatability and interchangeability among the different thresholding strategies for quantifying the CC.

RESULTS

A total of 72 optical coherence tomography angiography (OCTA) examinations were considered. The systematic review allowed us to conclude that three local thresholding strategies (Phansalkar, mean and Niblack) and three global thresholding strategies (mean, default, Otsu) have been used for CC quantification. These strategies were evaluated in our observational study. We found a high agreement within the same method in the quantification of FD number, mean FD size, total FD area and FD density but a poor agreement with different strategies. Local strategies achieved a significantly superior ICC than global ones in CC quantification.

CONCLUSIONS

In conclusion, the interchangeability of the CC quantification using different thresholding strategies is low, and direct comparisons should not be performed. Local thresholding strategies are significantly superior to global ones for quantifying CC and should be preferred. There is an unmet need for a uniform strategy to quantify CC in future studies.

Morphologic Features of Buried Optic Disc Drusen on En Face Optical Coherence Tomography and Optical Coherence Tomography Angiography

PURPOSE

To evaluate and compare the morphologic characteristics of buried optic disc drusen (ODD) and optic disc edema (ODE) by using en face optical coherence tomography (OCT) and OCT angiography (OCTA).

DESIGN

Retrospective, cross-sectional study.

METHODS

We reviewed the medical records of 61 patients (92 eyes) with buried ODD, 45 patients (62 eyes) with ODE, and 42 normal-appearing fellow eyes examined at 1 referral center between November 1, 2017 and April 30, 2019. Characteristic en face OCT and OCTA findings of buried ODD compared to those of ODE and normal optic discs were investigated.

RESULTS

On en face OCT, all buried ODD were visualized as hyperreflective kidney-shaped masses well demarcated from the optic nerve axons, whereas ODE was visualized as ill-defined boundaries confluent with the retinal nerve fibers. On OCTA, 25.0% of the eyes with buried ODD showed a C-shaped vessel density decrease in the nasal radial peripapillary capillary layer, while 40.3% of the eyes with ODE had nonspecific focal vessel density decrease around the optic nerve head. Larger ODD were significantly associated with a vessel density decrease on OCTA (P = .009). The disc diameter positively correlated with the ODD area (r = 0.245; P = .018) and negatively correlated with the ODD height (r = -0.237; P = .023).

CONCLUSIONS

En face OCT showed the characteristic features of buried ODD compared to those of ODE or normal optic discs. The demarcation of buried ODD from the optic nerve axons on en face OCT and the poor vascular perfusion of buried ODD on OCTA suggest that buried ODD are materials deposited around the optic disc rather than the herniated optic nerve axon fibers.

Normative Database of Peripapillary Vessel Density Measured by Optical Coherence Tomography Angiography and Correlation Study

Purpose: To provide a normative data set of swept-source optical coherence tomography angiography (SS-OCTA) peripapillary vessel density (VD) measurements and assess correlations with age, gender, disc area and axial length (AL). Material and Methods: This was an observational cross-sectional study conducted on 346 right eyes of healthy subjects. Peripapillary SS-OCTA VD measurements were obtained in the retinal superficial capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillaris (CC) in all four quadrants using the Triton device (Topcon, Nagoya, Japan). AL measurements were made by optical biometry. Results: Mean participant age was 37.7 ± 19.8 years (range 5- 83), AL was 23.9 ± 1.3 mm (21-27), and 59% were women. Mean VDs for all quadrants were 57.2 ± 5.7% for SCP (52.4 ± 4.0% - 62.1 ± 4.2%), 46.3 ± 6.5% for DCP (41.9 ± 5.8% - 49.7 ± 4.8%) and 60.8 ± 7.4% for CC (53.4 ± 5.8% - 65.7 ± 5.5%). Negative correlation was detected between SCP VD and age (R = -0.264; P < .001), while correlation between DCP densities and age was positive (R = 0.202; P = .002). No associations were detected between peripapillary VD and gender (P ≥ 0.087) and negative correlation was found with AL and disc area only in the CC (P ≤ 0.004). In a subgroup analysis of 33 individuals, we noted no differences in VD between fellow eyes (P ≥ 0.139). Conclusion: Peripapillary VD showed wide individual variation when measured with the Triton SS-OCTA in the different retinal plexuses and CC. While correlations were observed with age, no relationships emerged with gender and only CC showed negative correlation with AL and disc area.

Association of renal function with retinal vessel density in patients with type 2 diabetes by using swept-source optical coherence tomographic angiography

AIMS

To investigate the relationship between retinal vessel density and renal function in patients with diabetes mellitus (DM) using non-invasive optical coherence tomographic angiography (OCTA).

METHODS

This prospective cross-sectional study recruited ocular-treatment-naïve patients with DM registered in the community of Guangzhou, China. The retinal vessel density of the superficial capillary plexus in the macula was obtained by using swept-source OCTA imaging. The Xiangya equation was used to calculate the estimated glomerular filtrate rate (eGFR). Participants were divided into the following groups by eGFR: no chronic kidney disease (non-CKD), mild CKD and moderate-to-severe CKD (MS-CKD).

RESULTS

A total of 874 patients with DM (874 eyes), with a mean age of 64.8±7.1 years, were included in the final analysis. The vessel density was significantly lower in patients with CKD than in non-CKD patients in a dose-response pattern, with a parafoveal vessel density of 49.1%±2.1% in non-CKD, 48.4%±1.9% in mild CKD and 47.2%±1.7% in MS-CKD (p<0.001). The sparser retinal capillaries were related to lower eGFR (β=0.037; 95% CI 0.025 to 0.049; p<0.001) and higher microalbuminuria (β = -0.023; 95% CI -0.039 to -0.008; p=0.002). The eGRF was independently associated with parafoveal vessel density (β=0.029; 95% CI 0.016 to 0.042; p<0.001), even after adjusting for other factors.

CONCLUSION

Retinal vessel density decreased with renal function impairment, underlining the potential value of OCTA to detect early microvascular damage in the kidney in patients with diabetes.

Evaluation of Foveal and Parafoveal Microvascular Changes Using Optical Coherence Tomography Angiography in Type 2 Diabetes Patients without Clinical Diabetic Retinopathy in South Korea

The aim of this study was to investigate foveal and parafoveal microvascular changes in retinal vascular plexuses in patients with type 2 diabetes mellitus (DM) without clinical diabetic retinopathy (NDR) using optical coherence tomography angiography (OCTA) in South Korea. We included 64 patients in the NDR group and included 48 healthy control subjects for comparison. All subjects underwent ocular examination with visual acuity and wide-field fundus photos. Foveal and parafoveal vessel density and foveal avascular zone (FAZ) area (mm²) in the superficial capillary plexus (SCP) and deep capillary plexus (DCP) were analyzed. Foveal vessel densities in both the SCP and DCP were decreased in the NDR group compared to the controls (p = 0.034 and 0.001, respectively). Vessel densities in the superior and inferior parafoveae in the DCP were decreased in the NDR group compared to the controls (p = 0.006 and 0.034, respectively). The FAZs of the SCP and DCP were significantly different between the NDR group and the controls (p = 0.003 and 0.001, respectively). The average vessel densities of the SCP and DCP were not correlated with HbA1c, serum creatinine, or the duration of DM in the NDR group. We demonstrated that OCTA can identify early-stage DR before the manifestation of clinically apparent retinopathy in diabetic eyes. Diabetic patients without clinical DR have microvascular alterations (foveal vessel density, parts of the parafovea, and enlarged FAZ) in the SCP and DCP. Our results suggest that OCTA might be a promising tool for early detection of eyes with DR.

Normative database and determinants of macular vessel density measured by optical coherence tomography angiography

IMPORTANCE

To provide a normative vessel density (VD) database for the macula through swept-source optical coherence tomography angiography (OCTA) and to assess the main determinants of this measurement.

BACKGROUND

In contrast with dye angiography, the recently introduced OCTA technique allows for the non-invasive measurement of retinal and choroidal VD metrics.

DESIGN

Cross-sectional study.

PARTICIPANTS

The right eyes of 346 healthy subjects were studied. In 105 subjects both eyes were imaged.

METHODS

Foveal and parafoveal macular VD measurements were obtained in the retinal superficial capillary plexus (SCP), deep capillary plexus (DCP), and in the choriocapillaris (CC) layer. Also recorded were age, sex, axial length (AL), foveal and choroidal thickness (CT).

MAIN OUTCOME MEASURES

Normative database and determinants of macular VD measured by OCTA.

RESULTS

Mean participant age was 38.3 ± 20.1 years (mean ± SD) (range 5-83). Foveal VDs in the different plexuses were: SCP 22.1% ± 5.0% (7.3-35.1), DCP 19.9% ± 6.3% (6.9-51.2) and CC: 52.8% ± 4.3% (40.2-62.1). Parafoveal VDs ranged from 45.4% ± 3.7% to 51.8% ± 4.6%. Positive correlation was observed between foveal VD and foveal thickness (R = .327), as well as between parafoveal DCP VD and CT (R = .250;P ≤ .006), while correlation with age was negative in the SCP and CC (R = -.283;P < .001). No associations were detected between macular VD and sex or AL (P ≥ .05).

CONCLUSION AND RELEVANCE

Macular VD showed wide individual variation, was positively correlated with foveal thickness and with CT, negatively correlated with age, and showed no correlation with AL or sex.

Papillary Vessel Density Changes After Intravitreal Anti-VEGF Injections in Hypertensive Patients with Central Retinal Vein Occlusion: An Angio-OCT Study

PURPOSE

To investigate papillary microvascular changes in patients affected by macular edema due to Central Retinal Vein Occlusions (CRVO) after anti-Vascular Endothelial Growth Factor (VEGF) therapy.

METHODS

Prospective analysis of papillary and peripapillary vessel density (VD) changes in 18 eyes of 18 hypertensive patients affected by CRVO before and after the loading-phase of intravitreal Ranibizumab (IVR) injections. Data were quantitatively measured by optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) before as well as 1 month and 4 months after injections. The correlation between post-treatment best-corrected visual acuity (BCVA) and changes in the retinal microvasculature evaluated by OCTA was assessed. Results: 18 eyes of 18 consecutive patients with a known history of arterial hypertension and affected by an acute CRVO episode were enrolled. Central macular thickness (CMT) was significantly reduced after IVR injections (p < 0.001), while mean BCVA improved from 0.70 ± 0.26 logarithm of the minimal angle of resolution (logMAR) units at baseline to 0.25 ± 0.18 logMAR units after 4 months (p < 0.001). VD inside disc and peripapillary significantly increased (p < 0.001 and p = 0.01, respectively) after treatment.

CONCLUSIONS

OCTA showed VD increase in the papillary area in patients affected by CRVO after anti-VEGF therapy. This area could represent a new region of interest to study microvasculature changes concomitant with severe macular edema.