MICE procedure helps surgeons take on corneal neovascularization

Mitomycin intravascular chemoembolization (MICE) is a novel surgical technique pioneered in 2022. (Image Credit: AdobeStock/maxsim)

A new treatment may soon shift the treatment paradigm for patients with a range of corneal conditions and could prove to be an alternative to transplants.

Mitomycin intravascular chemoembolization (MICE) is a novel surgical technique pioneered in 2022 by Dean P. Ouano, MD, a cornea, cataract, and refractive surgery specialist at Coastal Eye Clinic and consulting associate faculty at Duke University’s Department of Ophthalmology.

“I think that most corneal specialists would agree that the treatment options for corneal neovascularization have been less than optimal,” Ouano explained.

According to Ouano, corneal neovascularization and lipid keratopathy are major causes of corneal blindness, and the treatment options to date include subconjunctival, intrastromal and topical anti-VEGF agents, laser ablation techniques, fine-needled monopolar diathermy, fine tip bipolar cautery, long-term topical steroids and long-term valacyclovir for HSV/VZV.

Ouano describes MICE as “an investigational procedure to eliminate corneal neovascularization and prevent vision loss in cases of lipid keratopathy threatening the visual axis.” What makes mitomycin (MMC) effective, he explained, is its direct cytotoxic effect on cultured pulmonary and umbilical vein endothelial cells. There is evidence that mitomycin causes irreversible destruction of vascular endothelium.

Ideal MICE candidates are patients with lipid keratopathy secondary to corneal neovascularization encroaching on the visual axis and with corneal disease and inflammation that are under control.

One ophthalmologist using the cutting-edge procedure is Kamran M. Riaz, MD, a clinical associate professor and director of Medical Student Research at the Dean McGee Institute at the University of Oklahoma.

“The MICE procedure consists of the intravascular infusion of mitomycin-C to cause vessel occlusion,” said Riaz, who has teamed with Ouano’s group and a group of researchers from Israel to conduct a larger case series on the technique.

“For years, for corneal neovascularization, we really didn’t have a good treatment,” Riaz noted. “We would do things like cautery, steroids, antivirals, subconjunctival bevacizumab (Avastin), thermal cautery, and/or using argon laser. Unfortunately, most of these treatments are ineffective or have unwantedly high rates of recurrence. We really didn’t have a way of definitively treating corneal neovascularization.”

Patient with corneal neovascularization, lipid keratopathy, and scarring with decreased visual acuity (20/125). MICE was performed. Three weeks later, there is dramatic improvement of the neovascularization and keratopathy. Six months later, the vascularization has not returned and the corneal scarring continues to slowly clear. The patient’s vision has improved to 20/40. (Images courtesy of Kamran M. Riaz, MD)

Riaz said that after hearing about Ouano’s procedure he became interested in it as an option for his patients.

“I’m doing more and more of these cases,” he said. “You take a very tiny needle, a 33-gauge needle, and cannulate these corneal vessels.”

According to Riaz, the vessels have to be a little bit large and beefy. Ideally, it works well for corneal neovascularization (KNV) secondary to HSV/HZV or KNV at the graft-host junction in corneal transplants.

“MICE can be used as a primary or preparatory procedure. In some patients, MICE can effectively eliminate vessels and prevent further vision loss. In other patients, the KNV can be quite dense, and the patient may need a corneal transplant. Unfortunately…a PKP in the presence of florid KNV has a very high chance of rejection. I’ve therefore used MICE in these patients to eliminate the KNV and then do a corneal transplant several months down the line, giving the…transplant a much better chance of success.”

That can be rewarding, Riaz observed, because transplants involving vascularized corneas generally have a high risk of failure and rejection. MICE is providing positive outcomes to the limited number of patients on whom he’s performed the procedure. Even after MICE, Riaz added, a transplant with human corneal tissue is preferable and keratoprosthesis should be limited to the most severe cases, like patients who have rejected multiple grafts.

“MICE is an outpatient procedure that should be performed in the operating room to ensure good anesthesia and proper rinsing of the ocular surface.… While the optics of an in-office slit-lamp are superior, I would caution performing this at the slit-lamp, given the well-known side effects of MMC if not removed from the ocular surface thoroughly. Immediately after the procedure, one may not be very impressed with the results, and there may be a ‘pizza-pie’…appearance due to intracorneal hemorrhage, but the actual resolution of the blood vessels can take anywhere from 6 weeks to 3 months.”

Response can vary, and Riaz motioned a female patient on whom he operated in August whose vision continues to improve with each follow-up visit.

Riaz and a colleague at the Dean McGee Eye Institute have teamed to do some 16 MICE procedures in the past year and are beginning to feel more comfortable with it. “MICE is something I can speak with the most enthusiasm about because I’m a big proponent of it,” he noted. “Dean is someone I look up to as a mentor and with whom I communicate regularly.”

Because the procedure has been used for less than 2 years, it can be difficult to determine just how much visual acuity patients will regain, but in the short-term Riaz is seeing visual improvement in patients, who undergo the surgery as a preventive measure, a therapeutic option, or a first step toward a corneal transplant.

“I have a full spectrum of patients where we were able to just completely destroy a blood vessel where it was not visually significant at all,” he said. “So we were able to just maintain them at 20/20 before they lost vision. I’ve had other patients where we’ve improved vision and avoided surgery, and I’ve had patients where we were able to kind of clear the playing field to set it up for successful surgery.”

Ouano concluded that, although technically challenging, MICE can be a vision-saving option for patients and that larger comparative studies with extended follow-up periods would help assess its safety and efficacy.

“Given the appropriate circumstances, MICE can spare a patient the need for corneal transplantation,” he said.

Kamran M. Riaz, MD
E: Kamran-Riaz@dmei.org

Riaz is a clinical associate professor and the director of Medical Student Research at the Dean McGee Institute at the University of Oklahoma. He has no financial disclosures to make related to this content.