Impact of Radial Optic Neurotomy on Ocular Microcirculation

Abstract

Purpose: : Radial Optic Neurotomy (RON) has become an important and promising surgical method to treat central retinal vein occlusion. The present study aims to objectify the effects of RON on ocular hemodynamics.

Methods: : 8 patients undergoing RON were subjected to color Doppler imaging (CDI) examination before and 2 to 4 months after surgery. At both time points retinal ischemia was estimated by fluorescence angiography. CDI was performed with a Siemens Elegra ultrasound set–up with a 7.5L40 probe at 6.5 MHz. Blood flow velocities in the short and long posterior ciliary artery, central retinal artery and ophthalmic artery were recorded.

Results: : In 5 patients visual acuity was improved after RON by 1 to 4 lines. This was associated with a lower degree of retinal ischemia in the fluorescence angiogram. All of these patients either had increased peak systolic velocity, end–diastolic velocity or time average mean velocity of the central retinal artery compared to the pre–operative situation. Beside the effect of RON on the central retinal artery another subgroup of 5 patients showed independently of the functional and morphological success of surgery a pronounced increase of blood flow velocity in the short posterior ciliary artery (mean peak systolic velocity increased from 8.7 ± 0.9 cms^–1 to 13.2 ± 3.5 cms^–1). No change of blood flow velocities was detected in the ophthalmic artery and the long posterior ciliary artery. All observed parameters did not change in the untreated fellow eye.

Conclusions: : Our data indicate that successful RON is associated with a detectable, but highly variable hemodynamic effect on the central retinal artery. Independent of the visual outcome 5 patients showed a pronounced increase in blood flow velocity in the short posterior ciliary artery. Both hemodynamic effects take place in vascular bed of the treated region of the eye, the optic nerve head. This leads to the conclusion that the RON procedure appears as an approach to influence ocular perfusion as it is hypothesized by the supporters of this surgery. The clinical and prognostic relevance of these findings needs to be clarified by future studies.

Keywords: vascular occlusion/vascular occlusive disease • blood supply • vitreoretinal surgery