Dr Didier Ducournau explains how the technique he invented based on a mistaken assumption has been refined over the last 21 years.
Back in 1985, when it was still believed that macular idiopathic epiretinal membrane (ERM) corresponded to a higher reflection from the retinal surface, Dr Didier Ducournau pioneered a technique he has since performed approximately 16,000 times: Internal Limiting Membrane (ILM) peeling.
The light-bulb moment
"I then discovered that I had a higher visibility of the membrane reflection, as the 5° tilted slit illumination highlighted the reflection much more than the 25° fibre illumination. After having removed the attached posterior hyaloid, I then naturally started to remove the ILM, which was presenting a lot of reflection."
And so, the ILM peeling technique was born. Nevertheless, the surgery was still several years away from becoming a first-line treatment.
"Even after I performed that first procedure, I did not begin to remove the ILM systematically," explained Dr Ducournau. "But in 1987 I had a second chance event: I married Yvette, an ophthalmic pathologist. I sent her 56 specimens of removed ILM, and in all of them she found a certain degree of gliosis: astrocytes and Muller cell endfeet, filled with glial filament protein (GFAP). This had never been seen in a normal retina, and so I concluded that the disease was this gliosis: I decided therefore to remove the ILM systematically during ERM surgery."
Understanding the process
It was only much later that Dr Ducournau realized that this astrocytic proliferation - this gliosis - was in fact a beneficial reaction from the retina. "It is the retina's attempt to fight against an oedema," Dr Ducournau clarified. "Yvette explained to me that in neuropathology the astrocytic proliferation appears at the periphery of a chronic ischaemia in order to limit the effect of the oedema and to repair the synapses.
"This means that when we remove a reflection (the gliosed ILM), we are extracting a healing process - the astrocytic proliferation," acknowledged Dr Ducournau, "but we also remove the Muller cell endfeet."
This theory is consistent with the findings of Professor Sebastian Wolf.1
Dr Ducournau believes that this may explain why ILM removal is an effective treatment.
According to Dr Ducournau, ILM removal has the same long-term results whether reflection, caused by astrocytic proliferation, is present or not. "In fact, in cases of macular oedema following retinal vein occlusion (RVO) or Irvine Gass, where the reflection is mostly absent, ILM removal remains an effective solution. This is amazing," he enthused.
Dr Ducournau believes this can be explained by the fact that Muller cell endfeet extraction acts as a trauma, inducing a retinal response: a Muller cell gliosis. Compared with the astrocytic gliosis, which acts only on the inner part of the retina, the Muller cell gliosis has a much stronger effect on the overall thickness of the retina, acting in the same way that, for example, the radial glia act after a trauma of the spinal cord.