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Vernon Chow, Louis Wei Yi Lim, Isaac Weijie Chay, Shoun Tan, Kai Xiong Cheong, Gabriel Tan, Srinivas R Sadda, Colin S Tan; Optical coherence tomography angiography evaluation of the parafoveal vasculature and its relationship with ocular factors. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5456. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The foveal avascular zone (FAZ) is known to vary in size among normal individuals and in ocular disease, and is usually assessed using fluorescein angiography. Optical Coherence Tomography Angiography (OCTA) allows the non-invasive assessment of the parafoveal vasculature, including the FAZ. We aimed to determine the size of the superficial and deep FAZ in healthy adults using OCTA, and to ascertain the effects of demographic and ocular parameters on the FAZ.
In a prospective cohort study of 170 eyes, healthy volunteers with no ocular diseases underwent OCTA scans using the AngioVue OCTA system (Optovue, Fremont, CA). Foveal-centered 3mm x 3mm scans were performed and the FAZ was independently graded by 2 reading-center certified graders using the ImageJ software. Ocular parameters such as central retinal thickness (CRT), axial length (AL) and spherical equivalent were also measured. Multiple linear regression analyses were performed to evaluate the impact of ocular factors on superficial and deep FAZ area. Intraclass correlation coefficients were used to assess the inter-grader agreement.
The mean age of our participants was 22.7 years (21 – 30, SD± 1.5). Of the 170 eyes, the mean AL was 25.4 mm, and the mean spherical equivalent was -4.3 D. The mean CRT was 260.6 µm (220 µm – 301 µm, SD ± 16.6). Mean superficial FAZ area was 0.25 mm2 (0.04 mm2 – 0.48 mm2) while mean deep FAZ area was 0.38 mm2 (0.12 mm2 – 0.66 mm2). The deep FAZ was significantly larger than the superficial FAZ (paired t-test, p<0.001). Females had a larger superficial (0.28 mm2 vs. 0.22 mm2, p<0.001) and deep FAZ (0.41 mm2 vs. 0.36 mm2, p=0.006). On univariate linear regression, both superficial and deep FAZ area had significant correlations with CRT, sex, AL and spherical equivalent, but not with age. By multiple linear regression analysis, superficial FAZ area varied significantly with CRT (p<0.001), sex (p=0.010) and spherical equivalent (p=0.028), while deep FAZ area was influenced by CRT (p<0.001), AL (p=0.004) and age (p=0.014), but not by sex.
Both the superficial and deep FAZ size varies significantly among healthy young adults. Factors such as CRT, sex, and spherical equivalent influence the size of the FAZ, and should be accounted for when assessing whether the FAZ appears abnormal.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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