Foveal avascular zone and vessel density in healthy subjects: An optical coherence tomography angiography study

Purpose: To report the normal characteristics and correlations of the foveal microvascular networks using optical coherence tomography angiography (OCTA) in a healthy Iranian population. Methods: Enface 3x3 OCTA images were obtained using the RTVue Avanti spectral-domain optical coherence tomography with AngioVue software (Optovue, Fremont, CA, USA). Foveal avascular zone (FAZ) area, central foveal point thickness and inner retinal thickness at the foveal center and the vascular density of the superficial retinal capillary plexus (SCP) and deep retinal capillary plexus (DCP) in the fovea were recorded. Results: Seventy normal eyes of 70 subjects (range, 9 to 71 years) were studied. Mean FAZ area was 0.32 ± 0.11 (range, 0.13-0.67) mm2 in SCP and 0.50 ± 0.13 (range, 0.19-0.94) mm2 in DCP. Mean SCP vessel density was 29.6 ± 4.7 (range, 16.3-40.3) in the fovea. Mean DCP vessel density was 27.0 ± 5.9 (range, 15.0-45.2) in the fovea. The FAZ area at SCP level was negatively correlated to the central subfield thickness (P < 0.001). The FAZ area at DCP level correlated negatively to the central subfield thickness and was significantly associated to age (both P < 0.001). The foveal SCP vessel density significantly correlated with foveal thickness and the foveal DCP vessel density correlated significantly with central foveal subfield thickness and was inversely related to age (all P < 0.05). Conclusion: In this study, central foveal subfield thickness was a major determinant of the FAZ size and foveal vessel density. Age was a determinant for FAZ area and whole image vessel density in DCP. © 2018 Medknow Publications.All Rights Reserved

Correlation of optic disc morphometry and optic disc microvasculature assessed with optical coherence tomography angiography

Objective: To compare optic disc microvasculature measurements to the disc morphometrics in normal eyes. Design: Cross-sectional study. Participants: Fifty-eight healthy subjects. Methods: Enface 4.5x4.5 mm optical coherence tomography angiography images were obtained from the optic disc of healthy individuals. The radial peripapillary capillary (RPC) and the nerve head (NH) en face images were obtained. Also, spectral domain OCT measurements of the peripapillary nerve fibre layer (NFL) thickness were recorded. Correlations of the vessel density and NFL measurements with optic disc morphometrics were analyzed. Results: Fifty-eight eyes of 58 patients were included. Mean peripapillary NFL thickness was 99.77 ± 8.47 μm. The mean disc area was 2.15 ± 0.34 mm2 (range, 1.48-3.02 mm2) with an average cup/disc area ratio of 0.27 ± 0.14 (range, 0.0-0.6). On the RPC en face image, the mean vessel density of the whole image, peripapillary, and inside disc was 55.52 ± 2.90, 62.42 ± 3.30, and 45.77 ± 9.24, respectively. On the NH en face images, the mean vessel density of the whole image, peripapillary, and inside disc was 55.69 ± 3.04, 60.15 ± 2.79, and 52.69 ± 5.31, respectively. The NH vessel density in the inside disc area correlated with the cup/disc area ratio (R = -0.44, p < 0.001). The association of RPC vessel density in the inside disc area with the cup/disc area ratio was significant (R= -0.88, p < 0.001). The RPC vessel density in the peripapillary area correlated with the cup/disc area ratio (R = 0.37, p = 0.004). Also, the RPC vessel density in the whole image was associated with the peripapillary NFL thickness (R = 0.32, p = 0.01). Conclusion: We observed a significant negative correlation between inside disc vessel density and cup/disc area ratio, but not to the disc area in normal eyes. In addition, the whole image RPC vessel density was revealed to be weakly correlated with the average RNFL thickness. © 2018 Canadian Ophthalmological Society

Correlation of optic disc morphometry and optic disc microvasculature assessed with optical coherence tomography angiography

Objective: To compare optic disc microvasculature measurements to the disc morphometrics in normal eyes. Design: Cross-sectional study. Participants: Fifty-eight healthy subjects. Methods: Enface 4.5x4.5 mm optical coherence tomography angiography images were obtained from the optic disc of healthy individuals. The radial peripapillary capillary (RPC) and the nerve head (NH) en face images were obtained. Also, spectral domain OCT measurements of the peripapillary nerve fibre layer (NFL) thickness were recorded. Correlations of the vessel density and NFL measurements with optic disc morphometrics were analyzed. Results: Fifty-eight eyes of 58 patients were included. Mean peripapillary NFL thickness was 99.77 ± 8.47 μm. The mean disc area was 2.15 ± 0.34 mm2 (range, 1.48-3.02 mm2) with an average cup/disc area ratio of 0.27 ± 0.14 (range, 0.0-0.6). On the RPC en face image, the mean vessel density of the whole image, peripapillary, and inside disc was 55.52 ± 2.90, 62.42 ± 3.30, and 45.77 ± 9.24, respectively. On the NH en face images, the mean vessel density of the whole image, peripapillary, and inside disc was 55.69 ± 3.04, 60.15 ± 2.79, and 52.69 ± 5.31, respectively. The NH vessel density in the inside disc area correlated with the cup/disc area ratio (R = -0.44, p < 0.001). The association of RPC vessel density in the inside disc area with the cup/disc area ratio was significant (R= -0.88, p < 0.001). The RPC vessel density in the peripapillary area correlated with the cup/disc area ratio (R = 0.37, p = 0.004). Also, the RPC vessel density in the whole image was associated with the peripapillary NFL thickness (R = 0.32, p = 0.01). Conclusion: We observed a significant negative correlation between inside disc vessel density and cup/disc area ratio, but not to the disc area in normal eyes. In addition, the whole image RPC vessel density was revealed to be weakly correlated with the average RNFL thickness. © 2018 Canadian Ophthalmological Society

Effect of segmentation error correction on optical coherence tomography angiography measurements in healthy subjects and diabetic macular oedema

Purpose To evaluate the impact of segmentation error on vessel density measurements in healthy eyes and eyes with diabetic macular oedema (DMO). Methods In this prospective, comparative, non-interventional study, enface optical coherence tomography angiography (OCTA) images of the macula from healthy eyes and eyes with DMO were acquired. Two expert graders assessed and corrected the segmentation error. The rate of segmentation error and the changes in vessel density and inner retinal thickness after correction of the segmentation error were recorded and compared between the two groups. Results 20 eyes with DMO and 24 healthy eyes were evaluated. Intergrader agreement was excellent (intraclass correlation coefficient �0.9) for all parameters in both groups. The rate of segmentation error was 33 and 100 in healthy and diabetic eyes, respectively (p0.05). However, the mean absolute change in the vessel density measurements was statistically significantly higher in the diabetic group (all p<0.05). The mean absolute change in superficial and deep inner retinal thickness was statistically significantly higher in DMO (p=0.02 and p=0.002, respectively). Conclusions In this study, misidentification of retinal layers and consequent vessel density measurement error occurred in all eyes with DMO and in one-third of healthy eyes. The segmentation error should be checked and manually corrected in the OCTA vessel density measurements, especially in the presence of macular oedema. © Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ

Effect of segmentation error correction on optical coherence tomography angiography measurements in healthy subjects and diabetic macular oedema

Purpose: To evaluate the impact of segmentation error on vessel density measurements in healthy eyes and eyes with diabetic macular oedema (DMO). Methods: In this prospective, comparative, non-interventional study, enface optical coherence tomography angiography (OCTA) images of the macula from healthy eyes and eyes with DMO were acquired. Two expert graders assessed and corrected the segmentation error. The rate of segmentation error and the changes in vessel density and inner retinal thickness after correction of the segmentation error were recorded and compared between the two groups. Results: 20 eyes with DMO and 24 healthy eyes were evaluated. Intergrader agreement was excellent (intraclass correlation coefficient �0.9) for all parameters in both groups. The rate of segmentation error was 33 and 100 in healthy and diabetic eyes, respectively (p0.05). However, the mean absolute change in the vessel density measurements was statistically significantly higher in the diabetic group (all p<0.05). The mean absolute change in superficial and deep inner retinal thickness was statistically significantly higher in DMO (p=0.02 and p=0.002, respectively). Conclusions: In this study, misidentification of retinal layers and consequent vessel density measurement error occurred in all eyes with DMO and in one-third of healthy eyes. The segmentation error should be checked and manually corrected in the OCTA vessel density measurements, especially in the presence of macular oedema. © Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ