June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
Circumpapillary retinal nerve fiber layer axon density is reduced in experimental glaucoma eyes.
Author Affiliations & Notes
  • Mitchell Sullivan
    Optometry, University of Houston, Houston, Texas, United States
  • Margaret Gondo
    Optometry, University of Houston, Houston, Texas, United States
  • Nimesh Bhikhu Patel
    Optometry, University of Houston, Houston, Texas, United States
  • Footnotes
    Commercial Relationships   Mitchell Sullivan None; Margaret Gondo None; Nimesh Patel None
  • Footnotes
    Support  NIH Grant P30 EY007551, T35 EY007088, R01 EY029229
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 931 – A0400. doi:
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      Mitchell Sullivan, Margaret Gondo, Nimesh Bhikhu Patel; Circumpapillary retinal nerve fiber layer axon density is reduced in experimental glaucoma eyes.. Invest. Ophthalmol. Vis. Sci. 2022;63(7):931 – A0400.

      Download citation file:


      © ARVO (1962-2015); The Authors (2016-present)

      ×
  • Supplements
Abstract

Purpose : Histological studies show that there is good correspondence between optical coherence tomography (OCT) determined circumpapillary retinal nerve fiber layer (RNFL) thickness and total retrobulbar axon counts. However, these relationships don’t include differences in axon size and distribution with circumpapillary location and disease. The purpose of this study was to determine the variability in axon size and density for six circumpapillary regions, in the non-human primate experimental glaucoma model.

Methods : Four animals with unilateral experimental glaucoma were included in this study. Following endpoint OCT imaging, animals were euthanized, and perfusion fixed with 4% paraformaldehyde. The eyes were enucleated and circumpapillary tissue ~600µm from the rim margin, for the temporal, superior-temporal, superior-nasal, nasal, inferior-nasal and inferior-temporal regions, was dissected. This tissue, was then placed in 2% glutaraldehyde/2% paraformaldehyde and processed for serial block face scanning electron microscopy (SBFSEM). 20x20x20µm SBFSEM volumes were obtained from each block at 100nm, and all axons were delineated for three frames (frame 10, 100, and 190) using imageJ.

Results : Endpoint OCT circumpapillary average RNFL thickness for experimental eyes were 49µm, 52µm, 76µm, and 84µm. For control eyes, the temporal sector had the highest axon density (1.9-3.2 axons/µm2), while the superior-nasal sector had the lowest (0.9-1.3 axons/µm2). This difference was maintained in eyes with experimental glaucoma. Although the mean axon diameter in eyes with experimental glaucoma (0.34±0.45µm) was less than that of control eyes (0.36±0.43µm, p<0.01), axon density in experimental glaucoma was reduced (control eyes 1.67 axons/µm2, experimental 1.27 axons/µm2, p=0.023).

Conclusions : To estimate retinal ganglion cell content from in vivo OCT RNFL scans, both circumpapillary location and stage of experimental glaucoma need to be considered. Although in vivo OCT measures of the temporal NFL are the thinnest, it has the smallest axons and greatest density. The smaller axon diameters in glaucomatous eyes could reflect a change in axon morphology, or a selective loss of larger axons.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Histogram of all axons quantified, showing axon diameter distribution differences between control and experimental eyes.

Histogram of all axons quantified, showing axon diameter distribution differences between control and experimental eyes.

×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×