Authors:Fang Zige, Yang Zefeng, Liu Xiaoyi, Xie Bin, Peng Yuying, Liu Yuhong, Liang Xiaohong, Lin Fengbin, Song Yunhe, Zhang Xiulan
Corresponding author:Zhang Xiulan,Email:zhangxl2@mail.sysu.edu.cn
Published:2026-08-10
DOI:10.3760/cma.j.cn115989-20260212-00077
ABSTRACT
Objective To evaluate alterations in macular microvascular fractal dimension (FD) and blood vessel tortuosity (BVT) in patients with primary open-angle glaucoma (POAG) using optical coherence tomography angiography (OCTA).
Methods A cross-sectional study was conducted. Early POAG patients (101 cases, 101 eyes) and healthy subjects (518 cases, 518 eyes) who underwent OCTA at Zhongshan Ophthalmic Center between July 2016 and July 2023 were included. Macular microvascular geometric parameters of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) were obtained from OCTA images and compared between two groups. Univariate and multivariate regression models were used to identify ocular factors associated with FD and BVT. This study followed the Declaration of Helsinki. The study protocol was approved by the Ethics Committee of Zhongshan Ophthalmic Center, Sun Yat-sen University (No. 2023 KYPJ356-4), and all subjects signed the informed consent form.
Results Compared with healthy control group, POAG group showed significantly lower FD in the SCP and higher BVT in both the SCP and DCP ( t=-5.947、5.028、3.926; all P<0.001). In the multivariate model, diagnosis of glaucoma and image quality score (IQS) were influencing factors for FD in the SCP (diagnosis of glaucoma: β=-4.99, 95% confidence interval[ CI]: -8.06–1.93, P=0.001; IQS: β=0.73, 95% CI: 0.57-0.90, P<0.001) and BVT in the DCP (diagnosis of glaucoma: β=0.12, 95% CI: 0.03-0.21, P=0.008; IQS: β=-0.007, 95% CI: -0.012–0.002, P<0.001).
Conclusions Compared with healthy controls, there were significant differences in FD and BVT of macular microvessels in patients with early POAG, and the diagnosis of POAG is associated with macular microvascular geometry parameters.
KEYWORDS：
Glaucoma;Optical coherence tomography angiography;Fractal dimension;Blood vessel tortuosity;Determinants
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Authors Info & Affiliations
Fang Zige
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou 510060, China
Yang Zefeng
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou 510060, China
Liu Xiaoyi
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou 510060, China
Xie Bin
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou 510060, China
Peng Yuying
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou 510060, China
Liu Yuhong
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou 510060, China
Liang Xiaohong
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou 510060, China
Lin Fengbin
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou 510060, China
Song Yunhe
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou 510060, China
Zhang Xiulan
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangdong Provincial Clinical Research Center for Ocular Diseases, Guangzhou 510060, China
Figures & Tables
Figure 1 Magnification correction by using Littmann and Bennett formula Scaling factor=3.382×0.013 062×(AL-1.82). The scaling factor was 1 if AL= 23.82 mm. En-face image of superficial capillary plexus at macula with AL=24.47 mm was presented and the scaling factor was calculated as 1.00 006. The green square corresponded to the actual image to the size of 6 mm×6 mm. The cropped images were involved in the final analysis OCTA: optical coherence tomography angiography; AL: axial length
Figure 2 Schematic illustration of the retinal microvascular fractal dimension measurement and parameter extraction OCTA images and the macula were automatically determined in B-scan images. Scan size of 6 mm×6 mm of an en-face blood flow image of both superficial and deep retinas were stratified. Original images with same scan size following projection artifacts removal were obtained. Then binarized and skeletonized capillary images were calculated. In the log-log plot, the blue dot represented actual OCTA data for this image, while the green line displayed the closest fitting fractal log-log line. The x-axis indicated the log base e of the size of the boxes in pixels, while the y-axis represented the log base e of the number boxes subtending the OCTA pattern. Thus, a linear relationship in the log-log plot indicating the good self-similarity of the macular retinal microvascular network OCTA: optical coherence tomography angiography
Figure 3 Schematic illustration of the retinal microvascular blood vessel tortuosity measurement and parameter extraction After binarization and skeletonization of the capillary OCTA images, distance parameters for calculating blood vessel tortuosity were extracted. Blood vessel tortuosity was calculated as the sum of the actual path lengths of the vessel branches divided by the sum of their straight-line distances BVT: blood vessel tortuosity; OCTA: optical coherence tomography angiography
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