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Diabetic retinopathy

There is still a role for laser and surgery in the anti-VEGF era

Dermot McGrath

Posted: Monday, October 2, 2017

Figure 1: 35-year-old man with extensive proliferative vitreoretinopathy in the nasal arcades dragging the macula towards the optic disc. At that time, BCVA was 20/400; Figure 2: After vitrectomy, bimanual dissection of the proliferative fibrovascular membranes, BCVA improved to 20/60

While the introduction of anti-VEGF therapies is transforming the clinical management of diabetic eye disease, laser and surgical options are still important treatments, reported researchers at the European Society of Ophthalmology (SOE) 2017 Congress in Barcelona, Spain.

For example, the success of anti-VEGF notwithstanding, focal laser photocoagulation still remains the gold standard in the initial treatment of the diabetic macular oedema (DME) disease, according to David Pelayes MD, Professor of Ophthalmology, Buenos Aires University, Argentina.

“We now have more options thanks to anti-VEGF therapies, but focal laser is not going to disappear from our treatment arsenal. Reducing the side-effects and improving the safety and efficacy of the therapy are some of the central aims of contemporary laser photocoagulation,” he said.

“Vision loss is mainly due to DME, which arises from leakage of plasma into the central retina. It has been reported that of patients who had been diabetic for 20 or more years, around 29% suffered from DME. Visual acuity is reduced irreversibly over time as the neurons involved die,” he said.

The Early Treatment Diabetic Retinopathy Study (ETDRS) showed that laser photocoagulation for DME helped reduce visual loss by 50% at three-year follow-up.

“However, traditional photocoagulation with grey or grey-white laser spots inevitably scars the retina, destroys photoreceptors and is associated with vision scotoma,” said Dr Pelayes.

Contraindications for focal laser treatment include ischaemic maculopathy, diffuse DME and patients who fail to appreciate the risk-benefit profile of the treatment, he added.

To try to minimise some of the side-effects, the parameters of laser photocoagulation have evolved in recent clinical studies by incorporating shorter pulse durations and lower laser energy, said Dr Pelayes.
“Clinical trials have demonstrated that lower energy can reduce side-effects and risks while effectively alleviating DME,” he said.

The general macular settings for the laser now include an exposure time of 10-to-20 milliseconds, resulting in sharply decreased energy density and thermal diffusion, he explained.

“Furthermore, studies have shown that the retinal photocoagulation induced by 10-to-30ms exposure time can stimulate inner retinal healing responses and is associated with less destructive effects than traditional methods,” he said.

NEW SURGICAL APPROACHES TO PDR
New techniques and instrumentation are also transforming the surgical management of proliferative diabetic retinopathy (PDR), José García-Arumí MD told delegates.

“New technologies have increased the anatomical and functional outcome in PDR, with tractional macular detachment still the first indication for surgery. Diagnostic advances such as wide-field angiography and swept-source OCT are also proving very helpful for the evaluation of ischaemia, traction and oedema,” said Dr García-Arumí, Full Professor of Ophthalmology, Universidad Autónoma de Barcelona, Spain.

PDR surgery outcomes have improved, due to advances in vitreoretinal instrumentation, techniques, perioperative medical management and changes in practice patterns, with earlier intervention leading
to better outcomes, said Dr García-Arumí.

“Innovations in small-gauge instrumentation have helped, as have the introduction of anti-VEGF therapies prior to surgery, and also at the end of surgery in cases of postoperative vitreous haemorrhage. Other approaches that have also helped include the use of viscodissection associated with the use of microincisions, the staining of membranes with blue dyes and the use of perfluorocarbon liquid and silicone oil in combined traction and rhegmatogenous retinal detachment,” he said.

The use of preoperative intravitreal anti-VEGF has produced promising results in some recent studies, noted Dr García-Arumí, leading to regression of retinal neovascularisation and facilitating fibrovascular membrane dissection with less intraoperative bleeding, less postoperative vitreous haemorrhage and reduced postoperative complications.

Furthermore, a 2013 meta-analysis of randomised controlled trials involving vitrectomy with or without preoperative intravitreal bevacizumab for PDR found compelling evidence for use of anti-VEGF therapy before surgery. Of 414 eyes of 394 participants in eight different trials, there was a shorter overall surgical time (mean difference 27 minutes), a smaller number of endodiathermy applications, less intraoperative bleeding and less recurrent vitreous haemorrhage for those who received bevacizumab before surgery.

However, Dr García-Arumí noted that some adverse consequences following anti-VEGF treatment in PDR have been reported, including a profibrotic switch comprised of a significant reduction in the neovascular component and marked increase in the contractile elements of the proliferative membranes over time.

The use of 23- and 25-gauge pars plana vitrectomy is gaining popularity, said Dr García-Arumí, with more stable fluidics from diminished flow, less bleeding and easily closed sclerotomies among the advantages of this approach. While smaller gauge instrumentation allows more precise dissection of membranes, it also poses higher difficulty at the periphery working through microcannulas, he explained.

David Pelayes: davidpelayes@gmail.com
José García-Arumí: jgarcia.arumi@gmail.com