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Different animal models have been developed for in-vivo study of retinal ganglion cells (RGCs). The B6.Cg-TgN (Thy1-CFP) 23Jrs/J mouse line is a popular one as the RGCs are intrinsically labeled with fluorescent proteins, and it has been shown that most of the CFP containing retinal cells are RGCs. Tosi et al. (1432) used a fluorescence microscope (FM) to image the Thy1-CFP transgenic mice in vivo and demonstrated progressive reduction of CFP expression after acute elevation of intraocular pressure and intravitreal injection of N-methyl-D-aspartic acid and kainic acid. Their findings are similar to previous studies using the confocal scanning laser ophthalmoscope (CSLO) (Leung, et al. Br J Ophthalmol 2009; 93: 964-968) and the fundus camera (Murata, et al. Invest Ophthalmol Vis Sci 2008; 49: 5546-5552).
Non-invasive imaging is a powerful technique to study RGC degeneration and would be a valuable tool in glaucoma research
However, FM appears to be inferior to CSLO and fundus camera in identifying and resolving individual retinal cells (Figs. 2 and 5). Most figures (3, 4 and 6) demonstrating reduction of RGC Thy1-CFP expression were shown in fixed retinal whole mounts. In Discussion, the authors pointed out that their Tg(Thy1-CFP)I reporter is RGCspecific (a gift from Feng. Neuron 2000; 28: 41-51) although they did not mention if there is any difference in the genetic make-up between their strain and the one available from the Jackson Laboratory (Bar Harbor, ME). While further validation of the FM imaging model would be needed, this paper delivers an important message that noninvasive imaging is a powerful technique to study RGC degeneration and would be a valuable tool in glaucoma research.