Purpose. The reflectance of the retinal nerve fiber layer (RNFL) arises from cylindrical light scattering elements distributed throughout its thickness (Knighton & Zhou, J. Glaucoma 4:117-123, 1995). The identity of these elements is unknown; a possibility is that they are axonal microtubules. We tested this possibility with the microtubule depolymerizing agent colchicine. Methods. We used imaging microreflectometry of ex vivo toad retina to measure RNFL reflectance at 440 nm. (The axons in toad RNFL, as in human, are unmyelinated.) After a period of baseline measurements, we changed the bathing solution either to one of identical composition (control experiments) or to one containing 10 mM colchicine. Results. After changing to colchicine solution, the RNFL reflectance declined slowly over 2-3 hours to a level 30-50% below baseline. Electron microscopy of colchicine-treated retina showed a similar decline in the density of axonal microtubules. In control experiments the RNFL reflectance remained within 10% of baseline. Conclusion. Microtubules make a major contribution to the light scattered by the unmyelinated axons of the toad RNFL, and may make a similar contribution to the reflectance of human RNFL.
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Feb 15 1996|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience