Abstract
Purpose :
In vivo blood flow information of choriocapillaris remains underexplored due to lack of appropriate technology. This study introduces and demonstrates the capability of OCT-based microangiography (OMAG) for non-invasive in vivo imaging of choriocapillaris in normal subjects, as well as the reliability of OMAG for quantifying normalized flux and normalized flow speed index to characterize choriocapillaris blood flow.
Methods :
A prospective, observational study. Eleven normal subjects (eleven eyes of random selection) were scanned by a Cirrus HD-5000 OCT-angiography prototype using 9 cubes montage mode with a FOV of 6.72mm*6.72mm. Ten subjects were scanned once and one subject was scanned three times for repeatability assessment. The choriocapillaris microcirculation was depicted as an en face image after segmentation with both OMAG mode and Doppler mode. Two unit less indices: normalized flux and normalized flow speed index were quantified from en face images. Two masked graders performed segmentation and data analysis of choriocapillaris in central fovea, parafovea and perifovea, separated into superior, inferior, nasal and temporal quadrants. Descriptive statistics, statistical test, repeatability and reproducibility were calculated.
Results :
Normalized flux increases from fovea centralis to parafovea and perifovea (p<0.0001, ANOVA), significant differences were also found among four quadrants (p=0.0032, ANOVA). No significant differences were found among fovea, parafovea and perifovea as well as among four quadrants for normalized flow speed index with ANOVA test, but fovea differs from perifovea (p = 0.0323, t-test). Mean, standard deviation and 95% CI were calculated for subfields and showed in figure. Both indices show higher repeatability (ICC = 0.966 and 0.927, for normalized flow speed index and normalized flux respectively) and reproducibility (ICC = 0.978 and 0.993, for normalized flow speed index and normalized flux respectively).
Conclusions :
OMAG can provide comprehensive blood flow information and characteristics of choriocapillaris. With normal database of normalized flux and flow speed index, OCTA can potentially serve as a diagnostic tool for early detection of dry AMD or other ocular diseases concerning choriocapillaris and help provide better understanding of RPE and choroidal diseases.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.