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Christopher Patrick Long, Mathieu Bakhoum, Christopher Brian Toomey, Dirk-Uwe G Bartsch, Eric Nudleman, Michael Henry Goldbaum, K Bailey Freund, David Sarraf, William R Freeman; Dilatation of the retinal capillary plexuses in branch retinal vein occlusion. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5736. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The retinal capillary system in the macula is arranged into three distinct layers, the superficial, intermediate and deep capillary plexus (SCP, ICP and DCP). Yet, the exact path of blood flow has been a matter of conjecture. A parallel organization implies independent arterial supply and venous drainage occurring at each layer. An in-series system implies arterial inflow to the SCP which then feeds into the ICP and then DCP where venous outflow originates. By utilizing optical coherence tomography angiography (OCTA) which is depth-resolved, we sought to examine whether the DCP is preferentially dilated in eyes with venous occlusion.
This was a retrospective case series that included patients presenting with branch retinal vein occlusion (BRVO). All patients had OCTA imaging. Exclusion criteria included poor quality OCTA imaging and any underlying macular pathology. En face OCTA was performed using the Angiovue (Optovue, Fremont, California, USA). For each eye, a 3x3 mm macular scan was obtained. Automated OCTA segmentation was performed and accurate segmentation was confirmed for each case. Capillary diameter was measured using diameterJ (open source plugin for NIH ImageJ, Hotaling et al. Biomaterials 2015; 61:327-38). Individual segments in the SCP images were obtained and analyzed after excluding large vessels. Changes in capillary diameter within the affected hemisphere were established by comparing them to the capillary diameter in the normal hemisphere within the same eye. The same measurements were repeated in the contralateral eyes that served as negative controls.
Six out of 10 patients (2 male and 4 female, mean age of 67 years), met the inclusion criteria. SCP diameter in the affected hemisphere increased by 4.2% (-4.1% to 8.6%), vs a decrease of 1.7% (-5.3% to 3.7%) in the contralateral eye, p = 0.03. DCP diameter in the affected region increased by 9.4% (-0.03% to 18.8%), vs 1.3% (-1.8% to 2.8%) in the contralateral eye, p = 0.02. The overall change in DCP diameter was greater than that of the SCP (9.4% vs 4.2%, p = 0.11).
In BRVO, both the SCP and DCP are dilated. Capillary dilatation was more pronounced in the DCP, albeit statistically insignificant. While this may suggest an in-series arrangement of the retinal vascular plexuses, independent autoregulation of each plexus may account for their relative susceptibility to dilatation.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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