May 2007
Volume 48, Issue 13
ARVO Annual Meeting Abstract  |   May 2007
Age-Related Losses of Retinal Ganglion Cells and Axons
Author Affiliations & Notes
  • R. S. Harwerth
    College of Optometry, University of Houston, Houston, Texas
  • J. L. Wheat
    College of Optometry, University of Houston, Houston, Texas
  • N. V. Rangaswamy
    College of Optometry, University of Houston, Houston, Texas
  • Footnotes
    Commercial Relationships R.S. Harwerth, None; J.L. Wheat, None; N.V. Rangaswamy, None.
  • Footnotes
    Support NEI grants R01 EY01139, and P30 EY07751
Investigative Ophthalmology & Visual Science May 2007, Vol.48, 492. doi:
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      R. S. Harwerth, J. L. Wheat, N. V. Rangaswamy; Age-Related Losses of Retinal Ganglion Cells and Axons. Invest. Ophthalmol. Vis. Sci. 2007;48(13):492.

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

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Purpose:: Age-related losseses in retinal nerve fiber layer thickness (RNFLT) areare assumed to be the result of an age dependent reduction of retinal ganglion cells (RGCs), but the rates are much different; published age-related losses in RGCs are about 0.65%/year, compared to 0.25%/year for thinning of RNFLT. To determine whether the neural bases for these aging effects are equivalent, the aging effects on estimates of RGCs from standard automated perimetry (SAP) and estimates of RGC axons by optical coherence tomography (OCT) were compared.

Methods:: Preliminary data were obtained from visual fields (normal GHT on SAP 24-2 fields) and RNFLT (standard OCT scan) of 32 patients (ages 20 - 71 years, median = 46). The SAP measures of visual sensitivity and OCT measures of RNFLT were used to estimate neuron counts by each procedure.

Results:: The age-related thinning of RNFLT was 0.3%/year when a constant axon density was used to derive axon counts from RNFLT, compared to 0.6%/year for the age-related loss of RGCs from SAP. Concordance between losses of axons and soma required an age-dependent reduction of 0.46%/year in the density of axons in the RNFLT.

Conclusions:: The results suggest that the proportion of RNFLT that is comprised of RGC axons is not constant across age, but rather a greater proportion of the total thickness is non-neural tissue for older patients and, thus, the dynamic range of RNFLT thinning from glaucoma is smaller. The difference in RNFLT changes from aging and glaucoma may reflect a difference in the site (soma vs. axon) of initial injury leading to cell death.

Keywords: perimetry • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • ganglion cells 

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