OPTIC-NERVE SHEATH DECOMPRESSION MAY IMPROVE BLOOD-FLOW IN ANTERIOR ISCHEMIC OPTIC NEUROPATHY

Purpose: The purposes of this study are to evaluate the retrobulbar circulation in progressive nonarteritic ischemic optic neuropathy (NAION) and to assess changes in blood flow after optic nerve sheath decompression (ONSD). Methods: Twenty-five patients with progressive NAION were studied using color Doppler imaging (CDI) before and after ONSD. Blood flow velocities and vascular resistance were calculated for the ophthalmic artery, central retinal artery, and posterior ciliary arteries in each eye. Contralateral eyes served as the control group. Results: Preoperatively, the study group demonstrated significantly lower blood flow velocities in the central retinal artery (P < 0.002) and posterior ciliary arteries (P < 0.02) when compared with the contralateral control group. Postoperatively, there was a significant increase in blood flow velocity in the ophthalmic artery (P < 0.04) and the central retinal artery (P < 0.05) as well as a significant decrease in vascular resistance in the posterior ciliary arteries (P < 0.02) in the study group. There were no significant changes in blood flow velocity or vascular resistance in the contralateral control group. Long-term follow-up on eight patients suggests a persistence of this trend. Seventeen of the 25 operated eyes demonstrated a postoperative improvement in visual function, defined as a gain of two lines or more in Snellen visual acuity or at least 20-degrees of visual field expansion. Conclusions: These data demonstrate that eyes with acute NAION have impaired blood flow when compared with the contralateral control group. Furthermore, they suggest that ONSD may improve blood flow to the ischemic optic nerve halting the progression of visual loss and in some cases improving visual function.