ILM removal increases ease, safety of subretinal injections

April 10, 2017

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.

Reviewed by Yuki Morizane, MD, PhD

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.

Dr. MoriazaneLocal 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.” 

The procedure

The local ILM removal is performed after small-gauge vitrectomy and ILM staining with brilliant blue G.

Dr. Morizane and colleagues described their novel approach in an article that was published in 2016 [Okanouchi T, et al. Retina. 2016;36(5):1035-1038].

In the published and presented cases, the technique was used to deliver recombinant tissue plasminogen activator in the management of submacular hemorrhage in eyes with macroaneurysm rupture, polypoidal choroidal vasculopathy, and age-related macular degeneration.

“The approach can also be applied to the use of subretinal injections for delivering gene therapy, in macular translocation surgery, when removing hard foveal exudates, and in planned foveal detachments to resolve diffuse diabetic macular edema,” Dr. Morizane said.

“Obviating the need for retinal puncture is particularly valuable for avoiding complications in some of those settings, such as in eyes where a dense submacular hemorrhage limits visualization of the subretinal space, in eyes with choroidal neovascularization where there can be an RPE detachment in proximity to the retina, and if the situation where there is no subretinal fluid,” said Dr. Morizane.

He also observed that while ILM removal in macular hole and epiretinal membrane repair surgery has been associated with complications, ILM removal to facilitate subretinal injection is safer because it involves a much smaller area of tissue.

"In addition, if the ILM removal is done at an extrafoveal site, the potential for anatomic and functional complications is probably reduced,” Dr. Morizane said.

 

Yuki Morizane, MD, PhD

E: moriza-y@okayama-u.ac.jp

Dr. Morizane has no relevant financial interests to disclose. This article is based on a presentation that Dr. Morizane delivered at Retina Subspecialty Day, held prior to the 2016 American Academy of Ophthalmology meeting.