HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Huang, X.-R. Articles by Knighton, R. W. Search for Related Content PubMed PubMed Citation Articles by Huang, X.-R. Articles by Knighton, R. W.

Microtubules Contribute to the Birefringence of the Retinal Nerve Fiber Layer

From the Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida.

PURPOSE. The retinal nerve fiber layer (RNFL) exhibits birefringence that is due to the oriented cylindrical structure of the ganglion cell axons. Possible birefringent structures include axonal membranes, microtubules (MTs), and neurofilaments. MTs are generally assumed to be a major contributor, but this has not been demonstrated. In this study, the MT depolymerizing agent colchicine was used to evaluate the contribution of MTs to RNFL birefringence.

METHODS. Retinal nerve fiber bundles of isolated rat retina were observed through an imaging polarimeter set near extinction. Images were taken over an extended period. During baseline, the tissue was perfused with a physiological solution. During a treatment period, the solution was switched either to a control solution identical with the baseline solution or to a similar solution containing colchicine. The contrast of nerve fiber bundles was used to follow change of RNFL birefringence over time.

RESULTS. When imaged by the polarimeter, birefringent retinal nerve fiber bundles appeared as either bright or dark stripes. Bundles displayed as bright stripes were used to follow changes in retardance. The contrast of nerve fiber bundles was stable in control experiments. However, in treatment experiments, bundles were bright during the baseline period, but the contrast of bundles decreased rapidly when the colchicine solution was applied; bundles were barely visible after 30 minutes of treatment. After 70 minutes, the bundle contrast was close to zero at all wavelengths studied (440–780 nm).

CONCLUSIONS. MTs make a significant contribution to RNFL birefringence. The decrease of RNFL birefringence in glaucoma may indicate a loss of MTs.

This article has been cited by other articles:

				C. Balaratnasingam, W. H. Morgan, V. Johnstone, S. J. Cringle, and D.-Y. Yu Heterogeneous Distribution of Axonal Cytoskeleton Proteins in the Human Optic Nerve Invest. Ophthalmol. Vis. Sci., June 1, 2009; 50(6): 2824 - 2838. [Abstract] [Full Text] [PDF]

				B. Fortune, G. A. Cull, and C. F. Burgoyne Relative Course of Retinal Nerve Fiber Layer Birefringence and Thickness and Retinal Function Changes after Optic Nerve Transection Invest. Ophthalmol. Vis. Sci., October 1, 2008; 49(10): 4444 - 4452. [Abstract] [Full Text] [PDF]

				M. S. Zaveri, A. Conger, A. Salter, T. C. Frohman, S. L. Galetta, C. E. Markowitz, D. A. Jacobs, G. R. Cutter, G.-S. Ying, M. G. Maguire, et al. Retinal Imaging by Laser Polarimetry and Optical Coherence Tomography Evidence of Axonal Degeneration in Multiple Sclerosis Arch Neurol, July 1, 2008; 65(7): 924 - 928. [Abstract] [Full Text] [PDF]

				B. Fortune, L. Wang, G. Cull, and G. A. Cioffi Intravitreal Colchicine Causes Decreased RNFL Birefringence without Altering RNFL Thickness Invest. Ophthalmol. Vis. Sci., January 1, 2008; 49(1): 255 - 261. [Abstract] [Full Text] [PDF]

				X.-R. Huang, R. W. Knighton, and L. N. Cavuoto Microtubule Contribution to the Reflectance of the Retinal Nerve Fiber Layer Invest. Ophthalmol. Vis. Sci., December 1, 2006; 47(12): 5363 - 5367. [Abstract] [Full Text] [PDF]