Reduced Macular Vascular Density in Myopic Eyes

Abstract

Background: Morphological changes of the vasculature system in patients with myopia have been observed by Doppler ultrasound and fundus fluorescein angiography (FFA); however, these studies have limitations. Doppler ultrasound provides low-resolution images which are mainly obtained from visualized large vessels, and FFA is an invasive examination. Optic coherence tomography (OCT) angiography is a noninvasive, high-resolution measurement for vascular density. The purpose of this study was to investigate the change of vascular density in myopic eyes using OCT angiography.

Methods: This cross-sectional study includes a total of 91 eyes from 47 participants including control, moderate, and high myopia that were evaluated by OCT angiography. Patients with myopia were recruited from the Refractive Department, Shenzhen Aier Eye Hospital, from August 5, 2015 to April 1, 2016. Emmetropic eyes were from healthy volunteers. The vascular density at macula and optic disc regions, ganglion cell complex (GCC) thickness, and retinal nerve fiber layer (RNFL) thickness were measured. Their relationships with axial length (AL) and refractive error were analyzed. One-way analysis of variance (ANOVA), Pearson's correlation, and generalized estimating equation were used for statistical analysis.

Results: Both superficial and deep macular vascular density were highest in control (25.64% ± 3.76% and 37.12% ± 3.66%, respectively), then in moderate myopia (21.15% ± 5.33% and 35.35% ± 5.50%, respectively), and lowest in high myopia group (19.64% ± 3.87% and 32.81% ± 6.29%, respectively) (F = 13.74 and 4.57, respectively; both P < 0.001). Both superficial (β = -0.850 and 0.460, respectively) and deep (β = -0.766 and 0.396, respectively) macular vascular density were associated with AL and spherical equivalent (all P < 0.001). Superficial macular vascular density was associated with GCC thickness (β = 0.244, P = 0.040), independent of spherical equivalent. The vascular density in optic disc region had no difference among the three groups, and it was not associated with AL, spherical equivalent, or RNFL thickness.

Conclusion: Our results suggested that with the increase of myopia, the vascular density decreased in macular region, but not in optic disc region.

Figure 1

Example of the cases which were excluded because of segmentation error due to retinoschisis (a and c) and signal strength <50 (b and d).

Figure 2

Retinal angiograms processed using Image J software. The original macula (a and e) and optic disc (c) angiograms were processed with an automated thresholding algorithm, and the binary images of vascular networks were created (b, d, and f). Vascular density was calculated automatically.

Figure 3

Bar charts showing the superficial macular vascular density and deep macular vascular density in control, moderate myopic, and high myopic groups. *P < 0.01 compared to control group, Least Significant Difference test.

Figure 4

Scatterplots showing the correlation between superficial macular vascular density and axial length (a) spherical equivalent (b) ganglion cell complex thickness (c) deep macular vascular density and axial length (d) spherical equivalent (e) ganglion cell complex thickness (f) papillary vascular density and axial length (g) spherical equivalent (h) retinal nerve fiber layer thickness (i). r is the correlation coefficient and P values were calculated by Pearson's correlation.

Figure 5

Optical coherence tomography angiography images of superficial macular vessels in eyes with various axial lengths: the axial length is 23.30 mm (a) 26.11 mm (b) 29.47 mm (c) 34.62 mm (d). Red and green lines show the optical coherence tomography segmentation for reconstruction of angiogram.

Figure 6

Optical coherence tomography angiography images of deep macular vessels in eyes with various axial lengths: the axial length is 24.19 mm (a) 26.47 mm (b) 29.47 mm (c) 34.62 mm (d). Green lines show the optical coherence tomography segmentation for reconstruction of angiogram.