Vitrectomy a viable option in select DME cases

Benefits go beyond the removal of vitreous tractions, specialist says.

Anselm Kampik

Vitrectomy is a valid treatment option for diabetic macular edema that has a tractional component and does not respond to anti-VEGF or laser therapy, according to a retina specialist.

With an incidence approaching 25% over a 10-year period, macular edema is a major eye problem in diabetes. Studies have shown that more than 40% of patients with type 1 diabetes will develop macular edema in their lifetime.

“What is even more important is that the incidence of [diabetic macular edema] is rapidly growing because diabetes is getting more frequent in our population,” Anselm Kampik, MD, said at the Euretina meeting in London.

Laser photocoagulation is still the gold standard for diabetic macular edema (DME) treatment, while a growing body of evidence indicates that intravitreal anti-VEGF, either alone or in combination with laser, might have a better effect.

However, not every patient with DME responds well to intravitreal drug therapy and/or laser photocoagulation, Dr. Kampik said. Vitrectomy is considered an alternative option, but Dr. Kampik questioned the rationale for it among these nonresponders.

Vitrectomy for DME is not yet fully understood, even though a number of papers on this topic have been published in the last 20 years, Dr. Kampik noted.

“We are just beginning to understand what makes this surgery work beyond the mechanical effect of vitreous removal,” he said.

A substantial basis for the use of vitrectomy lies in epidemiology: Nasrallah and colleagues showed that the incidence of posterior vitreous detachment in patients with macular edema is lower than in diabetics without macular edema. In another study, spontaneous resolution of macular edema was observed after posterior vitreous detachment in 55% of cases compared to 25% of cases without posterior vitreous detachment.

“What these studies tell us is that the vitreous does play a role. The attached vitreous is probably a risk factor for DME,” Dr. Kampik said.

More than mechanical effect

Several studies have shown that vitrectomy improves visual acuity in patients with DME. Such improvement, Dr. Kampik said, cannot be explained by merely the mechanical effect of removing vitreous traction. Macular edema is only one component of a broader condition of diabetic maculopathy in which ischemic processes and neuronal changes also occur.

The use of imaging techniques such as fluorescein angiography and high-resolution optical coherence tomography helps in distinguishing traction, edema and ischemia and determining which of these factors is the main cause of damage.

“Is the decreased visual acuity in a given patient associated with edema involving the center of the macula or is it mainly the foveolar ischemia? Does traction play a role or even other causes such as neuronal degeneration, which is very difficult to diagnose?” Dr. Kampik said.

The rationale for vitrectomy may be related to all of these factors.

“We want to remove the tractional forces from the retinal surface, and this is where we start from. But we remove the vitreous also for other reasons: By reducing the oxygen consumption of the vitreous, we increase the oxygen level in the posterior segment and therefore reduce retinal hypoxia and ischemia. By removing the vitreous collagen, which is rich in VEGF, we reduce the concentration of VEGF on top of the retina, where it is probably not reachable by anti-VEGF drugs,” he said.

A number of substances are also available to assist surgical management, including steroids for visualization of the vitreous and staining agents to visualize the vitreoretinal interface and internal limiting membrane (ILM).

ILM peeling

Despite a lack of supporting evidence in the literature, clinical experience suggests that ILM peeling is important to optimize the results of vitrectomy in this pathology, according to Dr. Kampik.

“In the cases where we peel it, we have a multilayered appearance of epiretinal tissue and cellular proliferation on a layer of native vitreous collagen. Maybe the mechanical removal of all epiretinal tissue would be almost impossible without ILM removal. ILM peeling is probably important to get rid of all epiretinal tissue and to avoid recurrences of epiretinal membranes,” he said.

For increased efficacy, vitrectomy can be combined with cataract surgery and IOL implantation, along with laser treatment or intravitreal anti-VEGF or steroid injection, at the time of surgery or at a later stage.

This type of surgery has a high rate of success, Dr. Kampik said.

“If we look through the literature, we find that in almost all cases, retinal thickness is reduced after surgery. A 40% visual improvement is reported, regardless of the prior presence of tractional membranes. We see a long-lasting effect that is different than we see from anti-VEGF alone,” he said. – by Michela Cimberle

References:

• Nasrallah FP, Jalkh AE, Van Coppenolle F, et al. The role of the vitreous in diabetic macular edema. Ophthalmology. 1988;95(10):1335-1339.
• Hikichi T, Fujio N, Akiba J, Azuma Y, Takahashi M, Yoshida A. Association between the short-term natural history of diabetic macular edema and the vitreomacular relationship in type II diabetes mellitus. Ophthalmology. 1997;104(3):473-478.

• Anselm Kampik, MD, can be reached at Ludwig Maximilian University, Department of Ophthalmology, Mathildenstr. 8, 80336 Munich, Germany; +49-89-51603800; fax: +49-89-51604778; email: anselm.kampik@med.uni-muenchen.de.
• Disclosure: Dr. Kampik has no relevant financial disclosures.

The author’s message is that, in selected cases, vitrectomy has to be kept in mind as an option in the management of recalcitrant diabetic macular edema, even if OCT does not show dense vitreomacular traction.

Conventionally, we manage diabetic macular edema with laser, anti-VEGFs, steroids or with a combination of these treatments. In obviously visible vitreomacular traction, surgery is the treatment of choice. What this article and the author’s experience does is to open up options further. Currently very few surgeons perform vitrectomy for diabetic macular edema in the absence of proven vitreoretinal traction. This article gives us a basis for offering the surgical option in cases that do not respond to less invasive treatment. It also prompts the vitreoretinal surgeon to routinely remove the internal limiting membrane in all cases of diabetic vitrectomies, when diabetic maculopathy is associated.

The author’s suggestions are indeed food for thought. Further experience in this approach to treatment of DME should clarify and answer the question: Which subset of recalcitrant DME would be best suited for surgery? Research should also address the question as to how vitrectomy is altering the internal milieu of the eye in favor of DME resolution and whether the same endpoint could be achieved by other less invasive means, such as pharmacological induction of PVD.

— Gopal Lingam, MD
Senior Consultant, National University Hospital, Singapore
Disclosure: Dr. Lingam has no relevant financial disclosures.