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Toco Yuen Ping Chui, Lawrence Geyman, Brian Krawitz, Shelley Mo, Richard B Rosen; Influence of axial length on foveal vascular network: an optical coherence tomography angiography (OCTA) study. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5751.
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© ARVO (1962-2015); The Authors (2016-present)
It has been hypothesized that retinal stretching induced by eye growth facilitates the development of foveal pit. This study investigated the associations between axial length and foveal vessel density using optical coherence tomography (OCTA).
Axial length measurement and OCTA imaging were performed on 40 subjects (40 eyes; age range: 14-73years; axial length range: 20.42-27.15mm). Axial lengths were measured using an IOL master (Carl Zeiss Meditec). 3x3 mm OCTA perfusion maps centered at the fovea were obtained using a commercial system (Avanti RTVue-XR, Optovue). On the OCTA perfusion maps, a region of interest (ROI) defined as the area within 200μm from the foveal avascular zone (FAZ) margin was generated using distance transformation. The foveal vascular network within the ROI was then skeletonized in a semiautomatic fashion using custom MATLAB programs. Total foveal vessel density, as well as quadrant-specific vessel densities (superior, inferior, nasal, and temporal) were computed as the length of vessels divided by the corresponding area. FAZ area and effective diameter were also obtained. Individual retinal magnification factor was corrected using axial length. Pearson’s correlation was used to analyze axial length vs foveal vessel densities.
Foveal vessel densities were found to decrease significantly with increasing axial length (p values < 0.05; correlation coefficients: total ROI=0.59; superior=0.41; inferior=0.40; temporal=0.53; nasal=0.53). Specifically, total foveal vessel density was reduced by 17% with 30% increase in axial length. With the same change in axial length, quadrant specific vessel density was reduced by 14%, 15%, 18%, and 21% at the superior, inferior, temporal, and nasal quadrant, respectively. No significant correlation was found between axial length and FAZ parameters.
Axial length elongation is associated with non-uniform decrease in foveal vessel density, resulting in a higher reduction rate at the temporal and nasal quadrants than that of the superior and inferior quadrants.
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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