INTRAORBITAL OPTIC NERVE CRUSH INDUCES PROGRESSIVE RETINAL GANGLION CELL LOSS

Abstract

Abstract: : Purpose: To investigate the effects of complete intraorbital optic nerve crush on retinal ganglion cell (RGC) survival at different survival periods. Methods: Adult Sprague–Dawley rats were anaesthetized and retinal ganglion cells (RGC) were retrogradely labelled with Fluorogold (3% fluorogold in 0.9% NaCl containing 10% DMSO) applied over the surface of both superior colliculi (SCi). Seven days later, animals were re–anaesthetized, the left optic nerve was exposed within the orbit and lesioned approximately 3 mms from the optic disc. Intraorbital optic nerve crush was achieved with fine angulated jeweller's forceps. RGC survival was estimated 5, 7, 9 or 12 days after injury by counting FG–labelled RGCs in twelve standard regions of the left (axotomized) and right (intact) retinas. Results: In control untouched retinas, the mean (±SD) densities of FG–labelled RGCs were 2113±144 (n=8) 12 days after FG application. Five, 7, 9 or 12 days after intraorbital optic nerve crush (IONC), the mean (±SD) densities of FG–labelled RGCs in the left axotomized retinas were 1947±181 (n=8), 1732±179 (n=5), 941±199 (n=8) or 709±30 (n=5), and represented 92%, 86%, 49% or 36%, respectively, of their contralateral intact retinas. Significant cell loss was observed between 7 and 9 days after injury. Conclusions: Intraorbital optic nerve crush at approximately 3 mms from the optic disc results in RGC loss that first appears between day 7 and day 9 after axotomy, thus providing a window for therapeutic intervention against axotomy induced RGC loss. These results further document the influence of the distance of the lesion from cell soma on the pattern of RGC death.

Keywords: ganglion cells • trauma • neuro–ophthalmology: optic nerve