The Use of Novel Optical Coherence Tomography Angiography to Study Macular Retinal Vascular Density for Different Refractive Errors

Objective: To evaluate the reliability of novel optical coherence tomography angiography (Angio OCT) in measuring macular retinal vascular density with different refractive powers. Methods: One hundred twenty subjects came to regular examination between April to October 2016 in Eye Hospital, Wenzhou Medical University were recruited for this prospective study and the right eyes were selected. Subjects were divided into three groups based on their spherical equivalent (SE): Low myopia group (SE≤-3.00 D), Moderate myopia group (from -3.00 D to -6.00 D) and High myopia group (SE>-6.00 D). Angio OCT (RTVue XR, Optovue, USA) was used to create the En-Face images and an automatic identification program segmented the retina and then calculated vessel density. Repeatability was assessed by within-subject deviation (Sw) and test-retest (TRT). And a Pearson correlation was used to assess the relationship among vessel density, refractive power and axial length. Results: The age range and SE of subjects was 22.00±5.60 years and -4.80±2.48 D. All three groups showed good repeatability in retinal vascular density calculations. The TRT values were all lower than 6.1%. When analyzing the vascular density of the four quadrants, the inferior quadrant showed larger values than the other three quadrants except for the moderate myopia group in which the repeatability of the nasal quadrant was the worst. Even so, there was no statistical significance found in the three groups. The correlation coefficient between foveal vascular density and refractive power and axial length was 0.19 (P=0.037) and 0.246 (P=0.007), separately. Conclusion: The Angio OCT demonstrates good reliability in measuring macular retinal vascular density and the foveal avascular zone (FAZ). Different refractive powers do not influence the validity of the results. In addition, refractive power and axial length have a weak positive correlation with foveal vascular density. Key words: repeatability; retinal vascular density; optical coherence tomography angiography; foveal avascular zone