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Laser induced chorioretinal venous anastomosis (CRVA) has been advocated by McAllister and Constable as a treatment for non-ischaemic central retinal vein occlusion (CRVO).1 This technique potentially offers a means of permanently bypassing the site of obstruction to venous outflow, which is thought to occur in the region of the lamina cribrosa. In ischaemic CRVO, the visual prognosis is usually much poorer, with devastating complications like neovascular glaucoma and progressive macular ischaemia.2 In this prospective study, we investigated the feasibility of laser induced CRVA in eyes with ischaemic CRVO, in view of the possibility of avoiding or lessening these severe complications.
Materials and methods
The classification of ischaemic CRVO was based on the presence of 10 disc diameter or more of capillary non-perfusion in the fundus fluorescence angiography (FFA), according to the criteria in the CRVO study.2 Approval from the ethics committee and informed consent from patients were obtained. Inclusion and exclusion criteria are shown in Table 1. All the laser treatment was performed by one of the authors (AK) who had successfully treated patients with non-ischaemic CRVO with a similar procedure. The site for attempts at the creation of anastomosis was in the inferotemporal and superonasal retina over a venous tributary of the retinal vein where it crosses over an underlying choroidal vein, at least 3 disc diameters away from the optic disc. Argon or diode laser with 50 μm spot size of 0.1–0.2 second’s duration and with a power level of 1.5–2.5 W was focused over the edge of the chosen retinal vein. Increasing power was used until there was haemorrhaging from the vein (Fig 1A). The bleeding was stopped by pressure on the eye with a contact lens.
Six eyes of six patients were included (Table 2). All of them had posterior vitreous detachment. Median follow up was 21 months (range 5–31 months). The median preoperative best corrected visual acuity (BCVA) was 3/200 (range, hand movement to 8/200). The median postoperative best corrected visual acuity (BCVA) was 2/200 (range, hand movement to 20/200). The median number of attempted anastomosis sites per eye was four (range, two to four). Through repeated ophthalmoscopic examination, FFA, and indocyanine green angiography, no functional anastomosis was found. A small nodular fibrotic scar was noted in each site (Fig 1B). No other significant laser related complication was found. One eye eventually developed rubeotic glaucoma.
In non-ischaemic CRVO, a successful CRVA was created in 33–54% of eyes.1,3 Laserphotocoagulation treatment parameters differed, because the superiority of one combination of parameters compared with another had not been demonstrated.3 In our study, it appears that argon or diode laser induced CRVA was not feasible in ischaemic CRVO. We attribute this to the severe endothelial cell damage secondary to ischaemia and venous thrombosis across the retinal circulation. In a dog model without retinal vein occlusion, a successful laser induced CRVA was shown to be lined by endothelial cells.4 Despite the failure to create functional CRVA, we did not encounter any adverse complication related to the laser treatment. The presence of posterior vitreous detachment in our patients might have lessened the chance of development of chorioretinovitreal neovascularisation. Successful CRVA in ischaemic CRVO has been reported to be established through pars plana vitrectomy with direct surgical puncture or erbium:YAG laser.5–7 This surgical approach may be a better option to create CRVA in ischaemic eyes, especially when the posterior hyaloid is still attached preoperatively.
Financial and proprietary interest: nil.
Financial support: nil.