Diabetic vitrectomy

There are numerous conditions that can make diabetic vitrectomy a nightmare, but modern vitreoretinal surgery offers approaches that can overcome many of the difficulties those situations present, according to Philip J Ferrone MD, Great Neck, New York, US. Vitrectomy in the case of a simple diabetic vitreous haemorrhage is generally fairly straightforward, he noted. However, some eyes will have co-morbidities and anatomical characteristics that can necessitate a more complex procedure, Dr Ferrone said. The problematic conditions occur in the anterior and posterior segment. The main problem they create is in the visualisation of the retina and vitreous. Problems in the anterior segment include neovascularisation of the iris, with or without blood in the anterior chamber, small pupils, dense cataracts and dense retrolenticular blood, Dr Ferrone said.

In the posterior segment the nightmare conditions include dense organised old vitreous haemorrhage, high traction retinal detachments, dense pre-retinal plaques, thin, avascular atrophic retina, and, worst of all, combined rhegmatogenous/tractional retinal detachment, he noted.

In cases where there is blood in the anterior chamber, a two-needle washout technique is generally sufficient. However, if the lens is not clear, cataract extraction may also be necessary, he noted.

In mild-to-moderate diabetic retinopathy, phacoemulsification and implantation of a posterior chamber IOL will generally produce satisfactory results. However, in the worst cases, it is necessary to clean out all vitreous gel to prevent the risk of anterior hyaloidal proliferation, he explained.

“Wide-field viewing optimises visualisation for moderately bad lens opacities and makes intraoperative combined cataract removal less common,†Dr Ferrone said.

Regarding retrolenticular haemorrhages, Dr Ferrone noted that it is generally possible to remove them when shaving the vitreous base. The vitreous base gel stabilises the haemorrhage. He added that dense vitreous haemorrhages are not the challenge they once were, thanks to the advent of high-speed vitreous cutters available today, including 25-gauge devices.

There are several strategies for preventing intraoperative bleeding in eyes with active proliferative diabetic retinopathy. First of all, patients should ideally be taken off any anticoagulation or antiplatelet drugs if possible. Where that is impossible, because of the risk of cardiovascular or cerebrovascular events, raising the IOP can reduce the bleeding to some degree, he noted. Valved cannulas are helpful in this instance, Dr Ferrone said.

In addition, the surgeon can perform intraocular cautery with either a single function or multiple function instruments. There is also the more modern approach of injecting the anti-VEGF agent bevacizumab (Avastin, Genentech/Roche) three to 10 days prior to surgery. “Avastin is our best weapon against intraoperative bleeding,†he said.

Another set of situations that can create serious difficulties for the vitreoretinal surgeon are posterior cortical vitreous adhesions. Their location can vary and they may be present around the fovea, along the vascular arcades, in the peripapillary area, and in the mid-peripheral area.

Dr Ferrone noted that eyes with broadly adhered and diffuse adhesions typically have atrophic retinas and most only require treatment with a high-speed mechanical vitrector with suction with no need for scissors. The surgeon can use a bimanual technique.

A bimanual technique is also an option when performing vitrectomy in eyes with broadly adhered posterior cortical vitreous with multiple, focal cellular pegs.

For the focal adhesions with broad fibrin and cellular plaques, a high-speed vitrector can isolate the plaques, but a pair of curved scissors may be necessary to gently separate the plaques from the retina, he said.

In eyes with combined tractional/rhegmatogenous retinal detachments arising from proliferative diabetic retinopathy, valved cannulas are particularly helpful, as is triamcinolone for visualising the vitreous.

In addition, using perfluorocarbon liquid as a third hand can make some of the more difficult manoeuvres easier. Scleral buckling is helpful if there are peripheral breaks, and silicone oil can be used as well in worst cases, Dr Ferrone continued.

He concluded his presentation by stressing that the best way to mange nightmare diabetic situations is prevention.