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Editors Selection IGR 16-4
Experimental Glaucoma: RNFL thickness in a primate glaucoma model
Comment by Jonathan Crowston on:
50385 Structural and functional abnormalities of retinal ganglion cells measured in vivo at the onset of optic nerve head surface change in experimental glaucoma, Fortune B; Burgoyne CF; Cull GA et al., Investigative Ophthalmology and Visual Science, 2012; 53: 3939-3950
One advantage of experimental glaucoma models is that the precise timing of the initiating insult is known. This permits investigation of the very early phenotypic changes associated with the disease being modeled. Brad Fortune and colleagues here examined very early changes in the structure and function of the optic nerve in an established laser-induced primate glaucoma model.
The key observation was that at the time of onset of the first measurable changes in optic nerve head surface topography (that defined the onset of early glaucoma) there was a significant reduction in RNFL retardance and mfERG signal, but no discernable change in RNFL thickness. RNFL thickness did not exhibit significant thinning until 15 days after the onset of surface topography change. These results support the hypothesis that measurable changes occur in the axon cytoskeleton prior to any detectable thinning of the peripapillary RNFL and that these changes in the axon cytoskeleton are already associated with a loss in retinal ganglion cell function. If RNFL thinning is ultimately associated with axon loss, then these early changes may herald a window where there is a potential for reversing RGC damage.
RNFL thinning per se may not be the most sensitive measure for detecting an optic nerve that is under stress and at risk of glaucoma progression
This elegant study now sets a stage for further work to determine whether these very early signals of a 'stressed' optic nerve are indeed reversible and whether therapies that can reverse these signs will subsequently prevent axon loss. A second point is that RNFL thinning per se may not be the most sensitive measure for detecting an optic nerve that is under stress and at risk of glaucoma progression.
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