Effects of steroid administration and transcorneal electrical stimulation on the anatomic and electrophysiologic deterioration of nonarteritic ischemic optic neuropathy in a rodent model.

PURPOSE: To elucidate the effectiveness of steroid administration and transcorneal electrical stimulation (TES) on anatomic changes and visual function in a rodent model of nonarteritic ischemic optic neuropathy (rNAION). METHODS: Methylprednisolone (20 mg/kg) was injected through a central venous catheter twice a day for 3 days. TES was delivered with biphasic square pulses of 1 ms/phase, 100 µA of current, and 20 Hz of frequency for 60 min 3 h after induction on the 1st, 4th, 7th, 14th, and 28th days. RESULTS: Intravenous infusion of methylprednisolone significantly decreased the degree of acute disc edema but did not preserve the inner retinal thinning, decreasing the amplitude of scotopic threshold responses (STR) and decreasing retinal ganglion cell (RGC) numbers in rNAION. TES preserved the decreasing STR amplitude and the decreasing RGC numbers in rNAION. CONCLUSION: Steroids are effective for reducing disc edema in the acute stage in rNAION. TES is effective for preserving decreasing RGC numbers and function in the chronic stage of rNAION.

Effects of L-arginine on anatomical and electrophysiological deterioration of the eye in a rodent model of nonarteritic ischemic optic neuropathy.

PURPOSE: The aims of this study were to clarify the effectiveness of L-arginine (1) for reducing the severity of anatomical changes in the eye and improving visual function in the acute stage of a rodent model of nonarteritic ischemic optic neuropathy (rNAION) and (2) in preventing those changes in anatomy and visual function. METHODS: For the first aim, L-arginine was intravenously injected into rats 3 h after rNAION induction; for the second aim, rNAION was induced after the oral administration of L-arginine for 7 days. The inner retinal thickness was determined over time by optical coherence tomography, and the amplitude of the scotopic threshold response (STR) and the number of surviving retinal ganglion cells (RGCs) were measured. These data were compared with the baseline data from the control group. RESULTS: Both intravenous infusion of L-arginine after rNAION induction and oral pretreatment with L-arginine significantly decreased optic disc edema in the acute stage and thinning of the inner retina, reduced the decrease in STR amplitude, and reduced the decrease in the number of RGCs during rNAION. CONCLUSION: Based on these results, we conclude that L-arginine treatment is effective for reducing anatomical changes in the eye and improving visual function in the acute stage of rNAION and that pretreatment with L-arginine is an effective therapy to reduce the severity of the condition during recurrence in the other eye.

Rodent model of nonarteritic ischemic optic neuropathy and its electrophysiological evaluation.

PURPOSE: Our aim was to establish a rodent model of nonarteritic ischemic optic neuropathy (rNAION). METHODS: To induce rNAION, after administration of Rose Bengal (RB) (2.5 mM), the small vessels of the left optic nerve were photoactivated using a 514-nm argon green laser with about 500-µm spot size for 12 s (RB-laser induction). To evaluate the induction, funduscopic examination, fluorescein angiography (FA), visualization of capillaries within the optic disc, histologic evaluation, and electrophysiological testing were performed. RESULTS: In the RB-laser-induction eyes, the optic disc became swollen on day 3 followed by atrophy on week 8. FA showed filling defects in the choroid and optic disc at an early stage, followed by hyperfluorescence at a late stage. The capillaries within the optic disc were reduced markedly. Histopathologic examination showed acellular nerve fiber layer (NFL) swelling anterior to the optic disc. The morphologic retinal changes were apparent only in the retinal ganglion cell (RGC) layer, with a reduction in the number of cells. Visually evoked potential (VEP) amplitude decreased significantly, but electroretinography (ERG) showed no significant difference. The positive scotopic threshold response (pSTR) was not reduced on the 1st day but was significantly reduced 3 days after induction. CONCLUSIONS: The findings are similar to human NAION. Therefore, RB-laser induction is well suited to establish the presence of rNAION.