CRVO: Laser anastomosis

Ian McAllister MBBS, FRANZCO

An argon laser-based technique appears to effectively treat the underlying cause of central retinal vein occlusion (CRVO), which is an obstruction to venous outflow and may lead to vision gains in a significant number of patients, Ian McAllister MBBS, FRANZCO told delegates attending the 15th EURETINA Congress in Nice, France.

The laser chorioretinal anastomosis (L-CRA) works to bypass the occluded central retinal vein by creating an anastomosis between a retinal vein and the choroidal venous circulation, and provides an alternative route for the obstructed venous blood to exit the retinal circulation.

The rationale for L-CRA stems from the limitations of anti-VEGF treatments, which essentially treat only the component of the CRVO-induced macular oedema caused by upregulated cytokines and not the underlying cause, said Dr McAllister, of Australia.

Studies have shown that raised venous pressure in occluded retinal veins can be up to 24 times the normal pressure and is a component of the macular oedema in CRVO, he explained.

“Given that we know that venous pressure is a significant but as yet unaddressed component of the macular oedema in CRVO, what can we do about it? It really has been the elephant in the room for too long,” he said.

Since L-CRA usually takes four to six weeks to become apparent, anti-VEGF agents should be deferred for at least one month prior to attempt and one month post attempt, said Dr McAllister.

“I would advise following up at monthly intervals for at least the first six months. Retinal ischaemia from any closure of the distal segment of the vein should be treated with segmental panretinal photocoagulation (PRP). Retino-choroidal neovascularisation from the L-CRA site can be easily controlled with anti-VEGF agents and PRP to any peripheral ischaemia,” he added.

The efficacy of L-CRA has already been demonstrated in the randomised Central Retinal Vein Bypass Study, said Dr McAllister. Some 113 patients who had between three and 12-months onset of non-ischaemic CRVO were
randomised to laser-induced chorioretinal venous anastomosis or sham treatment.

With a follow-up of 18 months, a successful L-CRA was created in 76.4 per cent of patients in the treatment group, and treated eyes that developed an L-CRA achieved an 11.7-letter mean improvement from baseline over the control group in that same period.

More recent studies looking at L-CRA treatment in combination with anti-VEGF agents also show promise as a means of producing better and more stable visual acuity with less reliance on continued intravitreal injections, concluded Dr McAllister.

Ian McAllister: ianmcallister@lei.org.au