Purchase this article with an account.
M. J. Kupersmith, Q. Zhou, G. Mandel, V. Atkinson, S. Anderson, R. Kardon; Retinal Nerve Fiber Layer Birefringence: Acute Reduction and Recovery in Optic Neuritis. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5664.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To determine if retinal nerve fiber layer (RNFL) birefringence, thought to be mostly associated with axonal microtubule density, is affected at the onset of optic neuritis and if it changes over 6 months.
10 subjects had prospective good quality imaging of both eyes with OCT (Stratus) for RNFL thickness and GDx (in ECC mode) for RNFL phase retardation at a mean 6.6 days of vision loss and at 1, 3 & 6 months. We analyzed RNFL measurements divided into 12 clock hour sectors at all visits. For each sector, we calculated percentage change in RNFL thickness for OCT and in RNFL phase retardation for GDx compared to the corresponding sector of the fellow unaffected eye. For each visit, the percentage birefringence change was calculated as the percentage phase retardation change minus the percentage RNFL thickness change per eye per sector and then averaged over the subjects. We evaluated the trends of mean overall change (across sectors) based on RNFL thickness, retardation, and birefringence.
The RNFL thickness was about 25% higher and retardation was about 7% higher compared to the fellow eye at baseline. Compared to the OCT thickness, GDx retardation was more stable over 6 months, with approximately 9% cumulative retardation reduction. (Figure shows change for OCT and GDx over 6 months). The 6-month cumulative amount of reduction in retardation (2%) was similar to the 6-month OCT thickness loss (8.6%) when compared to the fellow eye. The RNFL birefringence was approximately -17.7% at onset and rebounded at 6 months.
The acute calculated drop in birefringence may result from reduction in microtubule density due to intra-axonal swelling or microtubular alterations in response to injury or from extracellular edema. Some of this calculated reduction seems to be recoverable. Since OCT measures RNFL thickness and GDx measures RNFL retardation, combining the two may reveal information that distinguishes recoverable tissue swelling from permanent damage.
This PDF is available to Subscribers Only