purpose. To investigate the long-term longitudinal profile of retinal ganglion cell (RGC) damage after optic nerve crush with a new technique for in vivo imaging of RGCs.

methods. A blue-light confocal scanning laser ophthalmoscope (bCSLO; 460 nm excitation, 490 nm detection) was used to image Thy-1 CFP mice aged 6 to 9 months (n= 5) before optic nerve crush, weekly after crush for 3 weeks, and at weeks 10 and 50 after optic nerve crush. A sham procedure was performed in the contralateral eye, and it was imaged as a control. Corresponding retinal areas before and after optic nerve crush were compared, and the fluorescent spots were counted manually. The longitudinal profile of RGC degeneration was modeled and compared with one-phase and two-phase exponential decay equations.

results. A significant and progressive loss of fluorescent spots was found after optic nerve crush with 18.6%±2.3%, 11.3%±3.4%, 8.8%±5.3%, 4.2%±3.1%, and 3.3%±2.1% of Thy-1–expressing RGCs remaining at weeks 1, 2, 3, 10, and 50, respectively, after optic nerve crush (P< 0.001; n= 5). There was no change in the fluorescence density in the contralateral control (P= 0.893). Two-phase exponential decay (y= 0.03+ 0.83e− 2.78t+ 0.14e− 0.30t) was a better fit than one-phase exponential decay (y= 0.94e− 1.93t+ 0.06; P= 0.003) equations, with half-lives of fast phase and slow phase of 1.7 days and 16.3 days, respectively.

conclusions. The longitudinal profile of RGC degeneration after optic nerve crush is characterized by a two-phase exponential decay model. bCSLO imaging provides an efficient and noninvasive approach to the longitudinal study of progressive RGC damage.