Retrobulbar optic nerve diameter measured by high-speed magnetic resonance imaging as a biomarker for axonal loss in glaucomatous optic atrophy

Invest Ophthalmol Vis Sci. 2009 Sep;50(9):4223-8. doi: 10.1167/iovs.08-2683. Epub 2009 Apr 30.

Abstract

Purpose: To assess a novel magnetic resonance imaging (MRI) protocol for quantifying the optic nerve diameter (OND) as a measure of axonal loss in the optic nerve.

Methods: Included in the study was one eye each from 47 subjects, of whom 9 had no eye disease, 16 had preperimetric glaucoma, 11 had a glaucomatous mean visual field defect of <10 dB and 11 of >10 dB. Each subject underwent automated perimetry, scanning laser polarimetry, optic coherence tomography, scanning laser tomography, and ultrafast high-resolution MRI at 3 T. OND was determined 5, 10, and 15 mm behind the eye with a half Fourier-acquired single-shot turbo spin-echo (HASTE)-sequence requiring 1.5 seconds of data acquisition time per slice and providing a spatial resolution of 0.11 mm. A multiple linear regression model was applied to determine correlations (r) among the different techniques.

Results: The correlation (r) was <0.37 for OND measurements taken 5 mm behind the eye. At 10 mm behind the eye, r increased to 0.57 and was statistically significant in four out six instances. In the orbital apex 15 mm behind the eye, r reached a maximum of 0.80 and was statistically significant in all instances. OND correlated best with the retinal nerve fiber layer thickness measured by optic coherence tomography.

Conclusions: Retina- or optic nerve head-related surrogate markers for axonal content correlated closely with the OND, although only when it was measured in the orbital apex. High-resolution MRI using an ultrafast HASTE-sequence at 3 T proved useful for OND quantification and may be a valuable asset in future neuroprotection trials.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Axons / pathology*
  • Cross-Sectional Studies
  • Fourier Analysis
  • Glaucoma, Open-Angle / diagnosis*
  • Humans
  • Magnetic Resonance Imaging*
  • Middle Aged
  • Optic Atrophy / diagnosis*
  • Optic Disk / pathology*
  • Retinal Ganglion Cells / pathology*
  • Tomography, Optical Coherence
  • Vision Disorders / diagnosis
  • Visual Field Tests
  • Visual Fields