A-peeling Approach?

Filippo Pacini, the Italian anatomist who discovered the internal limiting membrane (ILM) around 170 years ago, would probably be surprised by the amount of time we spend talking about this tissue. One frequently raised question is: does the ILM need to be removed, in all cases of macular holes? The short answer is, no. For the longer answer, we should ask three questions: is ILM peeling in all cases necessary? If it’s not necessary, does it improve the odds of success? And finally, is it safe?

First, the issue of necessity: the most important pathologic tractional force in most macular holes is vitreomacular traction. We know this because in the era prior to ILM peeling, we were able to close 60 to 90 percent of holes with just the removal of the posterior hyaloid. We can also use pharmacologic agents like ocriplasmin to close holes – in the MVI-TRUST study, this was effective in about 40 percent of cases (1). We can also get a successful closure using other methods that separate the macular posterior hyaloid and spare the ILM, such as placing an intraocular gas bubble in the office without vitrectomy.  With today’s modern OCT imaging technology, I believe we can now preoperatively or intraoperatively identify those cases that may only require posterior hyaloid removal, potentially sparring additional retinal dissection.

Second, I will concede that ILM peeling does improve the chance of closure (and lessen the chance of reopening) and now using ILM removal we are guaranteed closure in nearly 100 percent of cases. But this benefit comes at the price of potential risks; when we remove the ILM, we not only remove the footplates of Müller cells, but also nerve fibers and glial cells. Most studies find little difference in visual outcomes when comparing peeling versus no peeling, but the majority of these studies used non-standardized visual acuity measurements, and had limited follow-up. Additionally, vision is only one measure of central visual function. One microperimetry study found microscotomas and decreased sensitivities in patients who had undergone ILM peeling, but not in non-ILM peeled patients (2). Visual field defects are also more common with ILM peeling versus no ILM peeling for macular holes (3). And we’ve seen that ILM-peeled patients display a decreased b-wave response in multifocal electroretinograms (4).

Additionally, most surgeons (in the United States at least) use indocyanine green (ICG) for intravitreal staining of the ILM, which has demonstrated retinal toxicity (5). In meta-analysis, it has also been associated with lower post-surgical improvements in visual function than patients who underwent an ILM peel without ICG being used (6).

In summary, ILM peeling is not necessary in all cases, but does improve chances of closure – with the tradeoff of exposing your patient to all of the risks inherent to the ILM removal procedure. With today’s technology, we’re better placed than ever before to identify patients who may only need the posterior hyaloid removed. In my practice today, I still remove the ILM – but it is becoming clear that in some cases, less may be more.