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The volume of peripapillary vessels within the retinal nerve fibre layer: an optical coherence tomography angiography study of normal subjects
  1. Davide Allegrini1,
  2. Giovanni Montesano2,
  3. Paolo Fogagnolo2,
  4. Alfredo Pece3,
  5. Roberta Riva2,
  6. Mario R Romano1,
  7. Luca Rossetti2
  1. 1Eye Unit, Humanitas Gavazzeni Hospital, Humanitas University, Bergamo, Italy
  2. 2Eye Clinic, San Paolo Hospital, University of Milan, Milan, Italy
  3. 3Department of Ophthalmology, Melegnano Hospital, Milan, Italy
  1. Correspondence to Dr Davide Allegrini, Eye Unit, Humanitas Gavazzeni Hospital, Humanitas University, Bergamo 24125, Italy ; davideallegrini{at}yahoo.it

Abstract

Background/aims To investigate the contribution of vascular volume calculated by optical coherence tomography angiography (OCTA) to the measurement of peripapillary retinal nerve fibre layer (RNFL) thickness.

Methods We used OCTA scans to build volumetric maps of the RNFL angiograms by thresholding the decorrelation images and summing the number of white pixels along the z-axis at each location. We used these maps to calculate the contribution of the vascular tissue to the RNFL thickness.

Results We analysed 51 eyes from 36 subjects. The mean RNFL volume calculated on the peripapillary region was 0.607±0.045 mm3 and the mean vessel volume was 0.217±0.035 mm3, with a mean vessel/total RNFL ratio of 35.627%±3.942%. When evaluated in the peripapillary circular section, the total contribution of the vascular tissue to the global RNFL thickness was 29.071%±3.945%. The superior and inferior sectors showed the highest percentage of vascular tissue within the RNFL circular profile (31.369% and 34.788% respectively).

Conclusions We found that the vascular contribution to the RNFL thickness is 29.07±3.945%. This is much higher than what has been reported from calculations made on the structural OCT alone (13% reported by Hood et al and 11.3%±1.6% for the Cirrus OCT and 11.8%±1.4% for the Spectralis OCT reported by Patel et al). We conclude that evaluation of the vascular tissue contribution to the RNFL thickness with OCTA might be useful when performing precise quantification of the neuronal tissue.

  • optic nerve fibers
  • RNFL thickness
  • peripapillary volume vessels.

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Footnotes

  • Contributors DA, GM, AP, PF contributed to conception and design; DA, GM, AP, RR, MR, LR contributed to acquisition of data; all authors contributed to interpretation of data; all authors drafted the article and approved the final version.

  • Competing interests None declared.

  • Ethics approval The Institutional Review Board (IRB)/Ethics Committee approval was obtained from Humanitas University Hospital (Rozzano, Italy).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement All data supporting our findings is contained within the manuscript.

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