Assessment of Choriocapillaris Flow Prior to Nascent Geographic Atrophy Development Using Optical Coherence Tomography Angiography

Purpose

To assess the relationship between choriocapillaris (CC) loss and the development of nascent geographic atrophy (nGA) using optical coherence tomography angiography (OCTA) imaging.

Methods

In total, 105 from 62 participants with bilateral large drusen, without late age-related macular degeneration (AMD) or nGA at baseline, were included in this prospective, longitudinal, observational study. Participants underwent swept-source OCTA imaging at 6-month intervals. CC flow deficit percentage (FD%) and drusen volume measurements were determined for the visit prior to nGA development or the second-to-last visit if nGA did not develop. Global and local analyses, the latter based on analyses within superpixels (120 × 120-µm regions), were performed to examine the association between CC FD% and future nGA development.

Results

A total of 15 (14%) eyes from 12 (19%) participants developed nGA. There was no significant difference in global CC FD% at the visit prior to nGA development between eyes that developed nGA and those that did not (P = 0.399). In contrast, CC FD% was significantly higher in superpixels that subsequently developed nGA compared to those that did not (P < 0.001), and a model utilizing CC FD% was significantly better at predicting foci of future nGA development at the superpixel level than a model using drusen volume alone (P ≤ 0.040).

Conclusions

This study showed that significant impairments in CC blood flow could be detected locally prior to the development of nGA. These findings add to our understanding of the pathophysiologic changes that occur with atrophy development in AMD.

Decreased Central Macular Choriocapillaris Perfusion Correlates With Increased Low Luminance Visual Acuity Deficits

PURPOSE

Correlations between low luminance visual acuity deficits (LLVADs) and central choriocapillaris perfusion deficits were investigated to help explain how increases in LLVAD scores at baseline predict annual growth rates of geographic atrophy (GA).

DESIGN

Prospective cross-sectional study.

METHODS

Photopic luminance best-corrected visual acuity (PL-BCVA) and low luminance BCVA (LL-BCVA) were measured using the Early Treatment Diabetic Retinopathy Study chart. LL-BCVA was measured using a 2.0-log unit neutral density filter. LLVADs were calculated as the difference between PL-BCVA and LL-BCVA. Within a fovea-centered 1-mm circle, the percentage of choriocapillaris flow deficits (CC FD%), drusen volume, optical attenuation coefficient (OAC) elevation volume, and outer retinal layer (ORL) thickness were assessed.

RESULTS

In all 90 eyes (30 normal eyes; 31 drusen-only eyes; 29 non-foveal GA eyes), significant correlations were found between the central CC FD% and PL-BCVA (r = -0.393, P < .001), LL-BCVA (r = -0.534, P < .001), and the LLVAD (r = 0.439, P < .001). Central cube root (cubrt) drusen volume, cubrt OAC elevation volume, and ORL thickness were correlated with PL-BCVA, LL-BCVA, and LLVADs (all P < .05). Stepwise regression models showed that central cubrt OAC elevation volume and ORL thickness were associated with PL-BCVA (R2 = 0.24, P < .05); central CC FD%, cubrt OAC elevation volume, and ORL thickness were associated with LL-BCVA (R2 = 0.44, P < .01); and central CC FD% and ORL thickness were associated with LLVAD (R2 = 0.24, P < .01).

CONCLUSIONS

The significant correlations between central CC FD% and LLVAD support the hypothesis that the ability of LLVAD to predict the growth of GA is mediated through a decrease in macular choriocapillaris perfusion.

Imaging biomarkers of leukaemic choroidopathy

PURPOSE

To longitudinally investigate choroidal and choriocapillaris perfusion metrics and the number of choroidal hyperreflective foci (HRF) in patients with acute leukaemia (AL) before and after disease remission and to correlate these metrics with systemic parameters during active disease.

METHODS

Prospective, longitudinal study of 26 eyes of 14 AL patients. All patients underwent optical coherence tomography (OCT) and OCT-angiography (OCTA) in the acute phase. Subfoveal choroidal thickness (CT), total, luminal and stromal choroidal area (TCA, LCA, SCA), choroidal vascularity index (CVI), choriocapillaris flow deficits (cFD) density, and choroidal HRF number were computed. In a subset, the measurements were repeated after AL remission. Age- and gender-matched 26 healthy controls were recruited for cross-sectional comparisons.

RESULTS

Patient's mean age was 59 ± 12 years. The TCA, LCA, SCA and choroidal HRF number were significantly higher in patients than controls (p = 0.028, p = 0.044, p = 0.024 and p = 0.001, respectively). Lower haemoglobin levels were associated with lower CT (r = 0.58, p = 0.008). Higher D-dimer values were associated with lower TCA (r = -0.52, p = 0.008), lower LCA (r = -0.50, p = 0.006), higher cFD density (r = 0.41, p = 0.044) and higher choroidal HRF number (r = 0.47, p = 0.008). The CT, TCA, SCA and choroidal HRF number significantly reduced after AL remission (p = 0.001, p = 0.047, p = 0.007 and p = 0.002 respectively). The CVI increased significantly compared to the active phase (p = 0.013).

CONCLUSION

The study demonstrates a subclinical choroidal involvement in patients with AL, with relative stromal thickening in the acute phase, and normalization after disease remission. Choroidal HRF were identified as a biomarker of leukaemic choroidopathy. Choriocapillaris and choroidal vascularity were inversely correlated with a systemic pro-coagulant state.

Choriocapillaris flow deficits in polypoidal choroidal vasculopathy using swept source optical coherence tomography angiography

Purpose:

To evaluate the choriocapillaris flow deficits (CCFD) on swept-source optical coherence tomography angiography (SS-OCTA) in eyes with unilateral polypoidal choroidal vasculopathy (PCV), fellow unaffected eyes, and to compare them with age-matched healthy controls.

Methods:

This study was a cross-sectional study which included treatment-naïve eyes with unilateral PCV (group 1), fellow unaffected eyes of patients with PCV (group 2), and normal eyes (group 3). Using the SS-OCTA, the Choriocapillaris (CC) slab was segmented from the structural optical coherence tomography (OCT) and the corresponding flow map was multiplied after signal compensation. The resultant image was evaluated for CCFD in equidistant squares measuring 1 × 1 mm, 1.5 × 1.5 mm, 2 × 2 mm, 2.5 × 2.5 mm, 3 × 3 mm, and 6 × 6 mm centered on the fovea.

Results:

The percentage of flow deficits were significantly increased (one-way ANOVA, P = 0.003 and P = 0.049) in the eyes with PCV as compared to the fellow eyes, and age-matched healthy controls. In the multiple pairwise comparison using post hoc Bonferroni, CCFD of 1 mm in group 1 and 2 (P = 0.019), group 1 and 3 (P = 0.003), and CCFD of 1.5 mm in group 1 and 3 (P = 0.044) were statistically significant. Correlation analysis showed no significant correlation between CCFD, age, Best corrected visual acuity (BCVA), foveal thickness (FT), and subfoveal choroidal thickness (SFCT) in our study. Linear regression analysis showed that the CCFD was negatively correlated with the distance from the foveal center in group 1 (β = −0.613, P = 0.046).

Conclusion:

Eyes with PCV demonstrated a significant flow impairment in the choriocapillaris layer as compared to the fellow unaffected eyes and age-matched healthy eyes.

Choriocapillaris Flow Deficits and Treatment-Naïve Macular Neovascularization Secondary to Age-Related Macular Degeneration

Purpose

To evaluate choriocapillaris (CC) flow deficits (FD) in eyes with treatment-naïve macular neovascularization (MNV) and to compare CC FD around exudative versus nonexudative MNV.

Methods

Treatment-naïve eyes with a diagnosis of either exudative or nonexudative AMD and type 1 MNV were included. Normal control eyes were age-matched to each AMD eye one to one. En face optical coherence tomography angiograms were analyzed for percentage of CC FD (FD%) in two concentric 500 µm rings, ring 1 and ring 2, surrounding the dark halo around MNV. The mean CC FD% in ring 1 and ring 2 was evaluated for each eye. A secondary analysis was similarly carried out to investigate the differences in CC FD% in exudative versus nonexudative treatment-naïve MNV.

Results

Twenty-three eyes with treatment-naïve MNV were age matched with 23 normal controls. The mean CC FD% was significantly greater in both rings in the MNV versus the normal control group (P < 0.05) and was significantly greater in the inner ring, closer to the lesion, than the outer ring. The mean FD% was also greater in both rings in the exudative versus the nonexudative MNV group, but this difference did not reach statistical significance.

Conclusions

The CC FD% was greater in the area surrounding MNV versus age-matched normal controls and in the ring closer to the MNV lesion. Further, CC FD was greater in eyes with exudative versus nonexudative MNV in both rings surrounding the associated dark halo, although this difference was not statistically significant.

Determination of Referential Rates for Optical Coherence Tomography and Optical Coherence Tomography Angiography Flow Deficits in the Macular Choriocapillaris in Ophthalmologically Healthy Children

Background and Objectives: Despite the growing number of new research publications, normative references for children's optical coherence tomography (OCT) parameters are still not completed. We chose to explore this topic because of the lack of normative parameters that is due to an improvement in different technologies and instruments. Our aim was to determine referential rates of retinal nerve fiber layer (RNFL) thickness and flow deficits (FD%) in the macular choriocapillaris (CC) in normal eyes of ophthalmologically healthy children. Materials and Methods: Ophthalmologically healthy 8- to 14-year-old individuals participated (n = 75) in this study. OCT images were taken using an swept-source-OCT (SS-OCT) instrument (DRI-OCT Triton, Topcon, Tokyo, Japan). The early treatment diabetic retinopathy study (EDTRS) grid (6 × 6 mm) divided the RNFL into the thickness maps. The FD% values of the CC were calculated on the 3 × 3-mm scans in a 1-mm circle (C1), 1.5-mm rim (R1.5), and the entire 2.5-mm circle (C2.5), and on the 6 x 6-mm scans in a 1-mm circle (C1), 1.5-mm rim (R1.5), the entire 2.5-mm circle (C2.5), 2.5-mm rim (R2.5), and 5-mm circle (C5). Results: Both scan quantifications of FD% in the C1, C2.5, and R1.5 sectors were similar, but the 6 × 6-mm scan measurements were statistically significantly smaller than the 3 × 3-mm ones. Significant moderate correlations were found between axial length (AxL) and FD% in the 6 × 6-mm scans, namely C1 (r = -0.347, p = 0.002), C2.5 (r = -0.337, p = 0.003), R1.5 (r = -0.328, p = 0.004), R2.5 (r = -0.306, p = 0.008), and C5 (r = -0.314, p = 0.006). Conclusions: The thinnest RNFL layers were on the temporal and nasal sides. FD% values in the C1, C2.5, and R1.5 sectors were similar between the 3 × 3-mm and 6 × 6-mm scans. The negative moderate correlations between AxL and FD% were found in all C1, C2.5, C5, R1.5, and R2.5 sectors of the 6 × 6-mm scans. Further prospective studies are needed to determine more accurate normative references for children's OCT parameters.

Quantifying choriocapillaris flow deficits using global and localized thresholding methods: a correlation study

BACKGROUND

To investigate the correlation and agreement of two previously published choriocapillaris (CC) quantification methods using a normal database with swept-source optical coherence tomography angiography (SS-OCTA).

METHODS

Normal adult subjects from all age groups imaged by SS-OCTA were used in this study. Each subject was imaged with 3 mm × 3 mm and 6 mm × 6 mm scan patterns centered on fovea, upon which en face CC images were generated by segmenting volumetric OCTA data. After signal compensation and removal of projection artifacts and noise, CC images were analyzed to identify flow deficits (FD) using two published methods. The first method utilized standard deviation from a young normal database (SD method) as the global thresholding while the second method utilized fuzzy C-means algorithm (FCM method) with local thresholding. Both methods segmented FDs from CC images and quantified FD density (FDD) and mean FD size (MFDS). In each 3 mm × 3 mm scan, three regions were quantified: a 1 mm circle (C1), a 1.5 mm rim (R1.5) and a 2.5 mm circle (C2.5). In each 6 mm × 6 mm scan, five regions were quantified: C1, R1.5, C2.5, a 2.5 mm rim (R2.5) and a 5 mm circle (C5). Spearman correlation and Bland-Altman plot analyses were conducted to compare the two methods.

RESULTS

Data obtained from 164 normal subjects (age: 56±19, 59% females) were used in this study. Strong correlations were observed between the two methods in all comparisons (r: 0.78-0.94, all P<0.0001). Overall MFDS provided higher or comparable correlation coefficients (r) compared to FDD. We have also observed stronger correlations in the central macula compared to parafoveal and perifoveal regions for both FDD and MFDS. In regions of C1, R1.5 and C2.5, 6 mm × 6 mm scans resulted in better agreement (smaller mean bias, similar or tighter limit of agreement) between the two methods for both FDD and MFDS compared to 3 mm × 3 mm scans.

CONCLUSIONS

There are strong correlations and satisfactory agreement between SD method and FCM method. SD method requires the reference to a normal database for CC quantification while FCM does not. Both methods could be used for the analysis of CC FDs in clinical settings depending on specific study designs such as the availability of a normal database.