Radial Optic Neurotomy Research Articles

Biomechanical Assessment of Radial Optic Neurotomy

A biomechanical model was constructed to simulate the potential therapeutic effect that the surgical procedure radial optic neurotomy (RON) would have on an eye with a central retinal vein occlusion. Experimental study. Model eyes undergoing RON were compared to control eyes under the same baseline conditions. Radial optic neurotomy. We modeled the optic nerve, lamina cribrosa, and the sclera separately and then reassembled the components. Material properties of the sclera and lamina cribrosa were extracted from the literature and both stiff and more elastic values were used for the optic nerve. Intraocular and arterial pressures were varied across a wide range in the analysis. Change in central retinal vein lumen size. Over a clinically relevant range of boundary conditions, the increase in the lumen area of the central retinal vein lumen after RON remained trivial, ranging from 1% to a maximum of 5%. The biomechanical effect of RON is negligible, and is unlikely to be a procedure that could mechanically ameliorate the clinical sequelae of a central vein occlusion.

Long-term effects of radial optic neurotomy for central retinal vein occlusion consecutive interventional case series

To investigate the long-term (minimum 24 months follow-up) clinical results of radial optic neurotomy (RON) following a pars plana vitrectomy (PPV) with internal limiting membrane peeling as treatment for central retinal vein occlusion (CRVO). Interventional case series of 14 consecutive patients (14 eyes) with CRVO who were treated with a PPV combined with RON within 1 year of diagnosis. Median baseline visual acuity (VA) was 1.05 logMAR (approximately 0.09 Snellen) in the affected eye. The follow-up period ranged from 24 to 48 months postoperatively, median 30 months. At the 24-month follow-up examination, median VA was 1.005 logMAR in the affected eye-a significant improvement (p = 0.013). Six patients (43%) gained 1 or more lines of VA (mean VA gain = 1.7 lines), while the VA of four patients (29%) improved by 3 or more lines. The eyes with nonischemic CRVO demonstrated a significantly higher improvement in VA (p = 0.0007) than the eyes with ischemic CRVO. With RON clinically relevant improvements on a long-term basis seem achievable. Patients with nonischemic CRVO may respond more favorably than patients with ischemic CRVO.

Radiäre Optikusneurotomie (RON) bei retinalen Zentralvenenverschlüssen

Compression in the lamina cribrosa is discussed as a reason for central retinal vein occlusion. Radial optic neurotomy should release the pressure and increase venous blood outflow. In a clinical trial 27 eyes with central retinal vein occlusion (22 eyes with clinical ischaemia, 5 eyes with continuous disc oedema and visual acuity below 4/10) underwent surgical decompression by vitrectomy and radial optic neurotomy. During surgery the intravenous pressure in the central vein was tested by infusion dynamometry before and right next to the incision. Follow up-time minimally was 1.5 years. Infusion dynamometry demonstrated a decrease of the central vein pressure right next to the incision in all eyes. In 17/22 eyes with ischaemic type of occlusion 6 weeks after surgery the relative afferent pupillary defect was lowered significantly and no growth of neovascularisations occurred. 5 eyes with persistence of the afferent pupillary defect received laser/cryocoagulation because of neovascularisations. After surgery visual acuity improved in 20/27 eyes and remained unchanged in 4/27 eyes. As complications we saw small subretinal haemorrhages at the neurotomy site (5/27), vitreous haemorrhages (7/27), hypotonia and choroidal detachment (1/27) and segmental visual field loss (14/27). The results of infusion dynamometry strongly support the hypothesis of a postulated compression of the central retinal vein in the lamina cribrosa. Functional results of radial optic neurotomy are superior to those of the natural course of ischaemic retinal vein occlusion in the literature, but visual field defects in association with the neurotomy site seem to be a serious side-effect of this therapeutic approach.

Chirurgische Therapie retinaler Venenverschlüsse

The range of therapeutic options for the treatment of retinal vein occlusions has been decisively extended by three new surgical methods: radial optic neurotomy (RON) and retinal endovascular lysis (REVL) for central retinal vein occlusion, and arteriovenous dissection (AVD/sheathotomy) for branch retinal vein occlusion. None of those methods has been tested in randomised studies meeting the requirements of evidence-based medicine. It is therefore difficult to assess the relative values of the individual procedures and determine in what precise circumstances each is indicated. The difficulties are compounded further by the use of these techniques in association with new and promising intravitreally injected drugs (e.g. steroids and angioinhibitors), which makes it even more difficult to assess the real efficacy of the surgical methods. In this paper we discuss the three different surgical methods and try to evaluate their clinical benefit.

Surgical macular decompression for macular edema in retinal vein occlusion

Background: Recently, a number of surgical and laser approaches have been used to improve visual outcome in cases of central retinal vein occlusion (CRVO) and branch retinal vein occlusion (BRVO). Intravitreal steroid injection alone appears to offer only temporary improvement at best. Radial optic neurotomy for CRVO and arteriovenous adventitial sheathotomy for BRVO are the most frequently utilized surgical procedures for these conditions, but evidence regarding efficacy is still lacking. We have suggested that macular decompression by internal limiting membrane (ILM) peeling may reduce macular edema and hemorrhage and improve visual acuity by relieving elevated intraretinal tissue pressure and facilitating egress of blood and extracellular fluid out of inner retinal layers into the vitrectomized vitreous cavity.Methods: 50 cases of severe visual loss due to macular edema caused by CRVO or BRVO, not eligible for laser photocoagulation, underwent pars plana vitrectomy with removal of preretinal hyaloid, peeling of the ILM stained with indocyanine green dye, air-fluid exchange, and postoperative prone positioning.Results: In all cases, intraretinal blood and retinal thickening diminished within 6 weeks of surgery. Visual acuity improved in 87% of CRVO cases and 68% of BRVO cases.Vision improved and stabilized at 39 days after surgery. Average improvement was 2.6 lines with a 6-line improvement in 1 case. There was no difference in outcome between cases with ischemic or nonischemic features on fluorescein angiography.Interpretation: Macular decompression using vitrectomy and ILM peeling is effective in the treatment of severe visual loss due to macular edema in CRVO and in those BRVO cases that do not qualify for laser photocoagulation.

Treatment of central retinal vein occlusion by radial optic neurotomy in 107 cases

To evaluate the potential role of radial optic neurotomy (RON), a new surgical technique has been recently proposed for treating central retinal vein occlusion (CRVO). It is hypothesized that CRVO constitutes a neurovascular compartment syndrome at the site of the lamina cribrosa, which can be alleviated by performing a radial incision at the nasal part of the optic nerve head, relaxing the cribriform plate and the adjacent sclera. One hundred and seven patients were treated with RON for CRVO at five collaborating ophthalmologic centers. All patients were evaluated by a standardized protocol. For analysis of the angiographic and fundus findings, reference images were used. Intraoperative and postoperative complications were reviewed. On 55 right and 52 left eyes of 107 patients (55.6% male, 44.4% female) with a median age of 68 years (range 21-91 years), RON was performed. The median follow-up time was 6 months (range 1-24 months). The median preoperative visual acuity (VA) was 0.05 (logMAR 1.3), increasing to a median postoperative VA of 0.08 (logMAR 1.1). Patients with an interval of more than 90 days between RON and onset of CRVO showed no significant change in VA at the 6-month follow-up. Severe peripapillary swelling of the optic nerve head prior to RON resulted in an average increase of 4.2 lines in VA at the 6-month follow-up. Angiographic findings of shunt vessels were seen in 18/30 cases after 12 months and were accompanied by an average improvement of VA of six lines. Visual field tests showed various defects in 86.8% of all cases. In one patient an iatrogenic injury of the central retinal artery occurred (0.9%). Despite the potential risk of visual field defects, RON seems to be a quite safe procedure. The majority of patients showed rapid normalization of the morphologic fundus findings, with an improvement in VA uncommon for the natural history of CRVO. No significant change in VA was seen in patients with an interval of more than 90 days between the onset of CRVO and RON. A prospective study is warranted for further investigation.

Imaging features after radial optic neurotomy in cat eyes

To evaluate the imaging features of cat optic disc after radial optic neurotomy (RON). A total of 10 healthy cats underwent RON unilaterally and examined by optical coherence tomography (OCT) and fundus fluorescein angiography (FFA) 1, 15, 30 and 90 days after the operation. One day after the operation, OCT showed that the depth of the incision reached the lamina cribrosa, with edema and thickening of the surrounding sensory retina. On the 15th day, the sensory retina edema and thickening were disappeared. On the 30th day, the depth of incision became shallow. Ninety days after the operation, the scar protruded from the lamina cribrosa. FFA examination showed that the incision appeared as hypofluorescence strip one day after the operation with retinal vessels leakage near the incision at vein phase. Incision was enlarged 15 to 30 days later, with hypofluorescence at early phase and partial staining at late phase. Ninety days after the operation, there was hypofluorescence at early phase and obvious scar staining at late phase. The imaging features of RON conform to a reparative process.

Chronic Angle-Closure Glaucoma Secondary to a Suprachoroidal Effusion Induced by Central Retinal Vein Occlusion

A 68-year-old woman presented to the ophthalmology emergency clinic with a painful left eye of a few hours' duration. One month prior, the patient had presented with a central retinal vein occlusion in the same eye. Examination revealed an intraocular pressure of 32 mm Hg in the left eye with 360 degree angle closure unaltered by indentation, a patent iridectomy from a previous combined phacoemulsification and trabeculectomy surgery, and no evident iris or angle neovascularization. Ultrasound biomicroscopic examination revealed a large suprachoroidal effusion with anterior rotation of the ciliary body and secondary angle closure in the left eye. The patient underwent successful pars plana vitrectomy, radial optic neurotomy, intra-vitreal triamcinolone acetonide injection, and goniosynechialysis.

Radial Optic Neurotomy for Management of Hemicentral Retinal Vein Occlusion

Radial Optic Neurotomy for Management of Hemicentral Retinal Vein Occlusion

Radial Optic Neurotomy for Management of Hemicentral Retinal Vein Occlusion—Reply

Radial Optic Neurotomy for Management of Hemicentral Retinal Vein Occlusion—Reply

Image features of fundus after radial optic neurotomy in cats' eyes

To evaluate the imaging features of cats' optic disc after radial optic neurotomy (RON). Unilateral RON were performed on 10 healthy cats. Optical coherence tomography (OCT) and fundus fluorescein angiography (FFA) were performed on the 1st, 15th, 30th and 90th day after RON. On the 1st d after the surgery, OCT showed that the depth of the incision reaching the posterior surface of luminal cribrosa, with the appearance of adjacent sensory retinal edema. The edema and thickening of sensory retinal disappeared 15 days after the operation. The depth of incision became shallow 30 days after the operation. On the 90th day, the scar filled the luminal cribrosa and the incision. FFA showed that the 1st d after the operation, blocked fluorescence was striped and retinal vessels leaked near the incision during the vein phase. The incision appeared as a spindle shape with hypofluorescence during the early phase and partial staining during the late phase 15 to 30 days after the operation. On the 90th day, there was obvious scar staining at the site that reached the cribriform and retina. The imaging features of RON are in accord with the reparative process.

Radial Optic Neurotomy in Central Retinal Vein Occlusion: Comparison of Outcome in Younger vs Older Patients

To evaluate the effectiveness of radial optic neurotomy (RON) for central retinal vein occlusion (CRVO) in patients < or =50 years of age (group 1) vs those >50 (group 2). Prospective, interventional, comparative case series. The study included 43 consecutive patients with CRVO and preoperative visual acuity (VA) < or =0.70 logarithm of minimal angle of resolution (logMAR). All patients underwent pars plana vitrectomy and RON at the nasal border of the optic disk. VA and optical coherence tomography (OCT) findings were recorded preoperatively and at one, six, and 12 months postoperatively. Systemic hypertension, diabetes, and open-angle glaucoma were statistically significantly more prevalent in group 2 (P < .05). One patient in group 1 had hyperhomocysteinemia, and had another antiphospholipid syndrome. Fifty percent of patients in group 1 gained > or =3 lines of Early Treatment Diabetic Retinopathy Study (ETDRS) vision, vs 33% in group 2. Mean final VA was 0.5 logMAR VA in group 1 vs 0.8 in group 2 (P = .04). Foveal thickness decreased significantly in both groups (P < .001). Ten patients (55.6%) in group 1 and 13 (54.2%) in group 2 developed retinochoroidal collaterals. Underlying systemic disease does not seem to be an important factor in the pathogenesis of CRVO in younger patients, and thrombophilia was present in only 11% of patients in this age group. RON yielded better functional results in younger patients, although functional improvement remained limited in those with low baseline VA.

Persistent serous retinal detachment after radial optic neurotomy

We report the case of a patient presenting with serous retinal detachment following radial optic neurotomy for central retinal vein occlusion. Initially, the retinal detachment was successfully treated by a second vitrectomy and laser coagulation. After reabsorption of the gas tamponade, a recurrence of the retinal detachment was seen with no detectable retinal break. Although other mechanisms should be taken into account, this case indicates that it is possible to create a fistula between the subarachnoid and subretinal space. We conclude from this observation that special attention should be paid to the depth of the radial incision into the optic nerve head.

Careful use of radial optic neurotomy for the treatment of retinal central vein occlusion

Radial optic neurotomy (RON) is an attractive and controversy procedure. Commenting on some disputed issues, the authors think that it seems inappropriate to negate the therapeutic effects of RON completely. However, it should be careful to select the proper patients for performing the RON. The indiscriminate extension of the indications of RON should be avoided.

Further evaluation of therapeutic effects for radial optic neurotomy

The purpose of this paper was to objectively evaluate the therapeutic effects and the complications of radial optic neurotomy (RON) in treating central retinal vein occlusion (CRVO). Aiming at the limitation of indications, uncertainty of therapeutic effects and safety of this procedure, it is important to have a prospective and controlled clinical trial, to establish an evaluation system based on evidence-based medicine for evaluating the clinical effects of this procedure.

VISUAL FIELD DEFECTS AFTER RADIAL OPTIC NEUROTOMY FOR CENTRAL RETINAL VEIN OCCLUSION

Surgical decompression of the vein in central retinal vein occlusion (CRVO) by radial optic neurotomy (RON) was recently proposed as being surgically feasible, safe, and beneficial. The effect of RON on the visual field has not been systematically reported, although possible visual field defects are expected due to iatrogenic cutting of the optic nerve fibers. The authors report the results of visual field testing in patients who underwent RON at the Tel Aviv Medical Center. Twelve consecutive patients (8 men, mean age of all patients 68 years) with nonperfused or indeterminate CRVO whose initial visual acuity (VA) was < or =20/400 underwent RON. Nine of these patients were able to perform visual field tests at 6 months post-RON and their visual field results are presented. : VA improved by > or =3 lines in 5 patients (42%). Three (25%) patients had a final VA of > or =20/200 and another had a final VA > or =20/50. Fundus and VA improvement were relatively slow. Two patients had clearing of the intraretinal blood, resolution of the venous dilation, and improved VA at the 2-month follow-up visit. Temporal visual field defects consisting of temporal ones that could be correlated to the site of the RON incision were detected in five out of the nine patients who were able to perform visual field tests. No temporal visual field defects were found in the remaining four patients, and three other patients were unable to perform visual field tests due to inability to identify the largest target size. VA improvement in 5 of 12 patients with ischemic or indeterminate CRVO following RON may be better than the natural history of CRVO. The risk of visual field defects may, however, be heightened by possibly cutting off blood supply to the optic nerve head and possible damage to nerve fibers in the optic nerve head, both inherent to the surgical procedure and both likely to produce visual loss.

Radial Optic Neurotomy for Management of Hemicentral Retinal Vein Occlusion

To evaluate the effect of radial optic neurotomy on visual acuity (VA) and foveal thickness in patients with hemicentral retinal vein occlusion. A prospective noncomparative case series of 13 eyes in 13 patients with hemicentral retinal vein occlusion and a preoperative VA of 20/60 or less from a total of 232 retinal vein occlusions diagnosed. All patients underwent pars plana vitrectomy, posterior hyaloid dissection, and radial optic neurotomy at the nasal border of the optic disc. Visual acuity and macular thickness were measured with optical coherence tomography. Nine patients (69.2%) gained 2 or more Snellen lines of vision, and in 4 patients (30.8%) VA improved by 4 or more Snellen lines (median visual acuity, 20/50; mean VA, 20/45; P<.01) (average gain, 2.7 Snellen lines). The decrease in foveal thickness was statistically significant (P<.01) (median decrease, 297 microm). Final VA was statistically related to decreased macular thickness at optical coherence tomography (P = .03; rho = -0.62). Retinochoroidal shunts developed in 6 patients (46.1%) at the radial optic neurotomy site. No surgical complications were observed. Radial optic neurotomy seems to be a potential treatment in selected patients with hemicentral retinal vein occlusion, probably because of the more rapid appearance of retinochorioretinal collateral vessels, which promote faster resolution of macular edema.

RADIAL OPTIC NEUROTOMY FOR THE MANAGEMENT OF HEMICENTRAL RETINAL VEIN OCCLUSION

To assess the efficacy of radial optic neurotomy (RON) for hemicentral retinal vein occlusion (hemi-CRVO) in patients with follow-up of >12 months. Five consecutive patients with hemi-CRVO were enrolled in the study and underwent vitrectomy with RON. The effects of this treatment were assessed by visual acuity, optical coherence tomography, indocyanine green angiography, and kinetic visual field testing. The median and mean visual acuities improved from 20/250 to 20/50 and from 20/286 to 20/51, respectively. Four patients (80%) had visual acuity improvement of > or =3 lines; visual acuity in 1 patient (20%) remained the same. Visual acuity in all four eyes with preoperative visual acuity of <20/200 improved to >20/200 12 months after surgery. Foveal thickness was gradually reduced during the follow-up period. Chorioretinal anastomosis was detected by indocyanine green angiography in 3 eyes (60%). A temporal visual field defect was found in two eyes. No neovascularization on the iris, angle, optic disk, or retina was detected postoperatively. Visual acuity may improve more with RON compared with the natural history of the disease, and no neovascular formation may occur after RON, suggesting that this procedure may be an effective treatment for hemi-CRVO.

Visual Field Defect After Radial Optic Neurotomy for Central Retinal Vein Occlusion

To evaluate visual field defects after radial optic neurotomy (RON) in eyes with central retinal vein occlusion (CRVO). Eight patients (eight eyes) underwent RON for macular edema associated with CRVO. Goldmann perimetry was performed on each patient both before and after surgery. Postoperative Goldmann perimetry showed a temporally located wedge-shaped visual field defect consistent with neural damage secondary to RON in seven eyes (88%). After surgery, the visual field decreased from preoperative values by 7% at 3 months (P = 0.30) and by 21% at 12 months (P = 0.0023). Although three patients (38%) were aware of the postoperative visual field defect, only one patient (13%) considered this defect to be a visual disability. After RON, most patients showed a postoperative defect in the temporal visual field consistent with the incision to the optic disk. However, this visual field defect appears to be well tolerated by most patients.

Wie tief muss die radiäre Optikusneurotomie zur Therapie des retinalen Zentralvenenverschlusses sein?

Most of the studies on radial optic neurotomy (RON) have not defined the depth of the incision. Complications following a deeper incision have been described. This histological study was performed to evaluate the required depth for RON. Serial sections of the area of the optic nerve head were performed in 19 eye bank eyes. The distance between the inner surface of the optic disc and the outer limit of the cribriform plate was measured. Ten additional eye bank eyes underwent 2 mm deep experimental RON using the Spaide CRVO Knife (DORC, Netherlands). The cutting depth was assessed histologically by serial cuts. The distance between the inner surface of the disc and the outer limit of the cribriform plate measured 1.35+/-0.3 mm (shrinkage-revised value: 1.45 mm). The experimental RON showed cutting depths of 1.53+/-0.3 mm (shrinkage-revised value: 1.65 mm). Based on normal eyes, a cutting depth of 1.45 mm is sufficient to cut through the cribriform plate. This might change during central retinal vein occlusion because possible papillary edema due to central retinal vein occlusion has to be considered. Even under controlled experimental conditions RON leads to great variation in incision depths. The development of a knife with a fixed penetration depth would be helpful.