title: 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.
  
  
  CONCLUSIONS
  Our results suggested that with the increase of myopia, the vascular density decreased in macular region, but not in optic disc region.
authors.affiliation: Aier School of Ophthalmology, Central South University, Changsha, Hunan 410015, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Fan
authors.affiliation: Joint Shantou International Eye Center, Shantou, Guangdong 515000, China.
authors.forename: Hao-Yu
authors.initials: HY
authors.lastname: Chen
authors.affiliation: Shenzhen Aier Eye Hospital, Shenzhen, Guangdong 518000, China.
authors.forename: Hong-Jie
authors.initials: HJ
authors.lastname: Ma
authors.affiliation: Shenzhen Aier Eye Hospital, Shenzhen, Guangdong 518000, China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Chang
authors.affiliation: Shenzhen Aier Eye Hospital, Shenzhen, Guangdong 518000, China.
authors.forename: Hai-Quan
authors.initials: HQ
authors.lastname: Yin
authors.affiliation: Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong 999077, China.
authors.forename: Danny Siu-Chun
authors.initials: DS
authors.lastname: Ng
authors.affiliation: Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong 999077, China.
authors.forename: Carol Y
authors.initials: CY
authors.lastname: Cheung
authors.affiliation: Aier School of Ophthalmology, Central South University, Changsha, Hunan 410015, China.
authors.forename: Shan
authors.initials: S
authors.lastname: Hu
authors.affiliation: Aier School of Ophthalmology, Central South University, Changsha, Hunan 410015, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Xiang
authors.affiliation: Aier School of Ophthalmology, Central South University, Changsha, Hunan 410015, China.
authors.forename: Shi-Bo
authors.initials: SB
authors.lastname: Tang
authors.affiliation: Shenzhen Aier Eye Hospital, Shenzhen, Guangdong 518000, China.
authors.forename: Shuang-Nong
authors.initials: SN
authors.lastname: Li
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D005123:Eye / Q000098:blood supply; D005260:Female; D005451:Fluorescein Angiography; D006801:Humans; D008266:Macula Lutea / Q000473:pathology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000473:pathology* / Q000503:physiopathology; D009898:Optic Disk / Q000473:pathology / Q000503:physiopathology; D011446:Prospective Studies; D012160:Retina / Q000473:pathology / Q000503:physiopathology; D012165:Retinal Ganglion Cells / Q000473:pathology; D041623:Tomography, Optical Coherence; D055815:Young Adult