ILM peeling is still controversial, surgeon says

Macular hole surgery does not appear to benefit significantly from internal limiting membrane peeling.

ByRochelle Nataloni

CLEVELAND, U.S.A. — Indications for peeling of the internal limiting membrane are hotly disputed, according to a presentation at the Cole Eye Institute Retina Summit here. British retinal specialist Zdenek J. Gregor, FRCS, FRCOphth, discussed peeling of the internal limiting membrane and its impact on macular hole surgery.

“It seems that ILM peeling may be useful in selected cases. However, I do not think that stage 2 holes require ILM peeling, and indeed probably most stage 3 holes do not require it either,” said Mr. Gregor, director of the medical retina service at Moorfields Eye Hospital in London.

There is increasing evidence that tangential traction alone is not the only reason why macular holes form, and that it is possible the initial mechanism may be antero-posterior traction, Mr. Gregor reported.

“However, the suggestion that the traction by the internal limiting membrane may perpetuate the presence of the macular hole and lead to its enlargement is generally accepted. Therefore, the rationale for removing the ILM would be to relieve the tangential traction that may be present to prevent new cellular proliferation and subsequent contraction, and it may well form a surgical adjunct,” he said.

ICG problems

According to Mr. Gregor, it has been suggested that only large holes, possibly chronic holes, holes that have failed to close or those that reopen are candidates. Opponents of that theory suggest that all macular holes — including small holes — should have their ILMs peeled.

“We know that stage 2 holes do universally well. In our trial, we had 100% closure rate of macular stage 2 holes without the peeling of the internal limiting membrane. Whatever you do to the stage 2 hole, it tends to close,” he said.

The ILM is thin and transparent, he pointed out.

“It breaks easily, and there is a learning curve involved in its removal,” he said. “Not only does the ILM like to break easily, it is sometimes very difficult to identify the edge. That is why staining of the ILM by using indocyanine green (ICG) dye seems quite helpful. The advantage is that the ILM becomes visible.”

However, according to Mr. Gregor, an increasing body of evidence suggests there are problems associated with the use of ICG.

“It has been found on a clinical ground that there are pigment epithelium alterations,” he said.

Phototoxicity has been invoked as one of the causes of this problem.

“It has been shown in the laboratory that retinal pigment epithelium absorbs light with greater facility when coated with ICG. It is also possible there is simply a prolonged tissue contact, because people simply marvel at what they can see and possibly take more videos,” Mr. Gregor said.

There is also some evidence that there could be direct tissue toxicity.

“Some surgeons use viscoelastic in order to avoid the contact between the pigment epithelium within the macular hole and the ICG,” he said.

Additionally, there is concern that the osmolarity of the solution typically used for ICG staining may be too high.

“It has been suggested that instead of diluting it with balanced salt solution, as we mostly do, that 5% glucose should be used to produce the appropriate osmolarity,” Mr. Gregor said.

The suggested dilutions vary, but generally, 5 mg/mL is used.

“There is growing evidence that very low concentrations can be used. These may not be visible when actually splashed across the ILM, but once the dissection is started, the edge becomes much more visible, even with very low concentrations. In fact, waiting for 30 seconds after the infusion is switched off may not be necessary either. Simply splash it on and take it off straight away,” he said.

Ticket to closure

Mr. Gregor said ILM peeling is a surgical challenge, with or without staining.

“There are potential complications of tissue staining, and it seems there is growing evidence and growing reluctance among colleagues to use ICG staining,” he said.

Is removal of the ILM a definite ticket to macular hole closure? Mr. Gregor reported on a comparative series that showed the closure rate is very similar with and without ILM peeling.

“In fact, the visual results are probably better with no ILM peeling,” he said.

One advantage, he suggested, is that once the ILM is peeled, much less tamponade time is needed.

Ultimately, he said, the problem is that to obtain definite evidence of beneficial effect of ILM peeling, a randomized trial would be desirable.

“But with such high [macular hole] closure rates, with or without ILM peeling, not too many of us are likely to start recruiting tomorrow,” Mr. Gregor said.

For Your Information:

Zdenek J. Gregor, FRCS, FRCOphth, can be reached at Moorfields Eye Hospital, City Road, London EC1Y2PD, England; +(44) 207-935-0777; fax: +(44) 207-935-6860.