Surgery in exudative AMD
Grazia Pertile MD
In an era when intravitreal anti-VEGF is the mainstay of treatment in exudative age-related macular degeneration (AMD), vitreoretinal surgery still has a fundamental role to play in managing patients with advanced disease, according to Grazia Pertile MD, who delivered the annual Gisbert Richard lecture at the 19th EURETINA Congress in Paris, France.
“This is rescue surgery, so obviously the indications for surgery are quite limited. Surgery can be considered when anti-VEGF therapy does not achieve an adequate response and the patient continues to lose vision, or when the complications of CNV cannot be managed with intravitreal injections alone such as a tear in the retinal pigment epithelium or in the presence of subretinal haemorrhage,” she said.She explained that two of the principal surgical options for advanced AMD include full macular translocation (FMT) and autologous choroidal transplantation.
FMT permits the relocation of the diseased macula on to an area of unaffected retinal pigment epithelial and choroid, and has been successfully used to restore the anatomy and visual function in some patients with AMD when the outer retina layers are not irreversibly damaged, noted Dr Pertile.
Vision-threatening complications after FMT surgery include cystoid macular oedema (CME) in 8% of cases, retinal detachment in 7.3%, proliferative vitreoretinopathy (PVR) in 4.2% and macular hole in 5.5%. She added that the presence of the external limiting membrane (ELM) seems to be the most reliable factor in predicting the functional outcome.
Vision-threatening complications associated with choroidal transplantation include late or no revascularisation of the graft in about 12% of cases, postoperative subretinal haemorrhage in 10%, retinal detachment with or without PVR in 4% and macular hole in 7%.
Although fast reperfusion of the choroid is a sign of successful surgery, a delay in reperfusion may lead to retinal damage and poor outcomes.
“Early reperfusion of the graft is crucial and it usually starts at the edge of the graft and proceeds quite slowly. We found in these cases that it can useful to scrape Bruch’s membrane – the idea is that the blood vessels come from the underlying choroid and sometimes Bruch’s membrane can block this reperfusion. After scraping using a subretinal spatula we usually encountered a high rate of reperfusion,” she said.
Dr Pertile added that RPE contiguity after autologous choroidal graft also seems to be a protective factor against atrophy progression, whereas any area of damaged or absent RPE tends to enlarge over time.
She noted that the incidence of retinal detachment and proliferative vitreoretinopathy (PVR) can be reduced with careful peripheral vitrectomy and removal of cortical vitreous remnants. It is also important to try to avoid contraction of the vitreous base by ensuring that the subretinal BSS injection is performed posterior to the equator. Likewise, performing a peripheral retinotomy close to the ora serrata helps to reduce the risk of PVR, she added.
Choroidal grafts should ideally be harvested away from large choroidal vessels outside the posterior pole to reduce the risk of postoperative subretinal haemorrhage. The risk of intraoperative bleeding can be minimised by increasing the IOP to around 70mmHg during the surgery, she said.
In trying to decide which surgical strategy to adopt, Dr Pertile said that FMT works best in patients with low best-corrected visual acuity in the fellow eye, with a subsequent risk of diplopia, as well as those with a healthy RPE-choroid area in which to relocate the macula. Choroidal graft may be considered in other cases that do fall into these particular categories.
Good functional results can be obtained over the long term with FMT, said Dr Pertile.
“We analysed 255 FMT cases in 2015 with 163 meeting the inclusion criteria and the majority of patients experienced an improvement in visual acuity. A few patients did lose vision, but the improvement for the majority of patients was maintained for up to five years after surgery. Patients with foveal RPE atrophy, CNV recurrence, and PVR carried a worse prognosis,” she concluded.