Take-home: Removing a small area of internal limiting membrane at the intended site of a subretinal injection allows the injection to be delivered without penetrating the retina.
Local removal of the internal limiting membrane (ILM) allows subretinal injections to be performed with greater safety and consistency, said Yuki Morizane, MD, PhD.
Introduction of this novel and simple technique was based on the idea that the ILM, which contains collagen Type IV and other extracellular matrix proteins, is the major source of resistance when attempting to puncture the retina with a flexible cannula.
Data collected in a series of 10 consecutive eyes that underwent subretinal injections showed that without initial removal of the ILM, the injection could not be delivered, even when applying pressure of up to 12 psi.
When the ILM was removed, however, the injection was performed successfully, without penetrating the retina and using only 6 psi pressure. No intraoperative or postoperative complications occurred.
“Applying excessive pressure in order to puncture the retina can cause damage to the retina, the retinal pigment epithelium (RPE), and the choroid that can lead to complications, including retinal and/or subretinal hemorrhage, RPE tears, and choroidal neovascularization,” said Dr. Morizane, assistant professor of ophthalmology, Okayama University Graduate School, Japan.
“After removing the ILM, it becomes possible to simply place the cannula tip on the surface of the retinal nerve fiber layer and inject fluid subretinally without having to penetrate the retina,” Dr. Morizane added. “Consequently, this technique avoids any risk of damage to the RPE and choroid.”