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Lisa Nivison-Smith, Matthew Trinh, Michael Kalloniatis; Quantity and morphology of inner retinal vasculature is reduced in intermediate Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3443. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Recent studies using optical coherence tomography angiography (OCTA) suggest vascular density of the inner retina is reduced in early Age-Related Macular Degeneration (AMD). However, it is not known whether these changes are due loss of blood vessels or simply reduction in vessel calibre. The relationship between these changes and AMD severity is also unclear. This study characterizes the quantity and morphology of retinal vasculature in a cohort of eyes with intermediate AMD to determine the origin of inner retinal vascular change and its utility as an AMD biomarker.
En face macula OCTA images of the superficial (SCP) and deep capillary plexus (DCP) from the Zeiss Cirrus Angioplex 6x6mm scans of 51 normal eyes and 63 eyes with intermediate AMD (based on the Beckman classification system) were extracted and quantified for vascular density (number of pixels contributing to blood flow/total pixels in image); total vessel length (number of pixels contributing to blood flow in skeletonised image) and average vessel diameter (vascular density/vessel length). Vascular morphology was characterized through vessel complexity index ([vessel perimeter]2/total area) and number of branches using the ‘Analysis skeleton’ tool in ImageJ. Parameters were correlated with drusen area from the 'Advanced RPE Analysis' tool of the Cirrus OCT.
Vascular density was significantly reduced in the superficial but not the deep capillary plexus in AMD eyes (SCP: p < 0.05; DCP: p = 0.06). Total vessel length (SCP: p < 0.05; DCP: p < 0.01) and average vessel diameter (SCP: p < 0.01; DCP: p < 0.001) was also significantly reduced in both layers of AMD eyes suggesting changes in vascular density could be related to loss of vessels as well as vessel constriction/thinning. Vascular complexity was decreased in both layers and the number of vessel branch points significantly reduced in the DCP (p < 0.01) indicating decrease in vessel length was likely due to loss of entire vessels. Interestingly, no parameters showed significant correlations with total drusen area.
Intermediate AMD appears to affect both the quantity and morphology of inner retinal vasculature but is not necessarily governed by other clinical signs such as drusen. This suggests AMD extends beyond the outer retina and may differ in its pathogenesis in the inner retina.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Superficial capillary plexus of intermediate AMD eye
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