Correlation of intraretinal thickness and microvasculature in healthy subjects

Abstract

Purpose : The goal of this study is to determine the relationship among retinal blood flow velocity, intraretinal layer thicknesses and microvascular network in the macular region of healthy subjects.

Methods : Retinal microvessel blood flow velocity and network in the wide field (35 degrees: 7.3 x 7.3 mm²) centered on the fovea (Fig. 1) was acquired using Retinal Function Imager (RFI, Optical Imaging Ltd, Rehovot, Israel). For measuring microvascular network density, fractal analysis using the box counting method (D_box representing density) was performed. The density of microvasculature in a diameter of 6mm circle centered on the fovea was measured after removing of the large vessels (diameter ≥ 25 µm). Custom made ultra-high resolution optical coherence tomography (axial resolution ~3 µm) was used to acquire three dimensional volumes of the macula and the intraretinal layers. The dataset was acquired twice using the macular cube 512 × 128 protocol (128 consecutive line scans) in an area of 6 × 6 mm² centered on the fovea. Automated segmentation software (Orion, Voxeleron LLC, Pleasanton, CA) was used to segment the retinal dataset into thickness maps of 6 intraretinal layers in a diameter of 6 mm centered on the fovea. Nineteen healthy subjects were recruited.

Results : Averaged arteriolar blood flow velocity was 4.0 ± 0.4 mm/s (mean ± SD) and averaged venular blood flow velocity was 3.2 ± 0.3 mm/s. The average Dbox of the microvessels was 1.803 ± 0.012. Total macular thickness was 382 ± 15 µm. The thicknesses of intraretinal layers are listed below the figure. Only the thickness of outer plexiform layer (OPL) was significantly correlated with both arteriolar velocity (r = 0.54, P < 0.05) and venular velocity (r = 0.62, P < 0.05), whereas the total macular volume, and the other intraretinal layer thickness were not correlated with blood flow velocity. No correlation was found between microvascular density (Dbox) and intraretinal layer thickness (P> 0.05).

Conclusions : This is the first study to explore the correlations among intraretinal layers, retinal blood flow velocity and microvascular network density in healthy subjects. The significant correlation between OPL and retinal blood flow velocities may be due to the inclusion of deep capillary network into the OPL measurement.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.