Clinical experience suggests that a corneal inlay (Kamra, AcuFocus) produces better visual and clinical results when implanted deeper than recommended by the product labeling. While the inlay’s instructions for use indicate the creation of a stromal pocket with a minimum depth of 200 μm for placement, implanting the device at 250 μm or deeper produces more stable refraction and improved visual acuity. (The target-depth for the intrastromal pocket should be between 200 and 250 μm.)
“Don’t be afraid to place [this inlay] deeper than the labeling,” said Phillip C. Hoopes Jr., MD, Hoopes Vision Center, Salt Lake City. “Our experience shows that your patients will reap a very clear clinical reward.”
Dr. Hoopes highlighted 12-month outcomes for the first 2 years of corneal inlay implantations performed at the Hoopes Vision Center. The retrospective case analysis study compared visual results for 75 inlays implanted less than 250 μm deep and 58 inlays implanted between 250 and 300 μm.
Patients in the two groups were similar. The average preoperative spherical equivalent for the shallow-implantation group was -0.45 D compared with -0.49 D for the deep-implantation group. Average patient age was 53 years.
“We began by seeing clinical results that were similar to the FDA study,” Dr. Hoopes said. “Some patients were having a hyperopic shift in their prescriptions, usually 3 to 6 months after surgery.
“During the first Kamra inlay user group meeting in 2015, surgeons began sharing their experience with implanting the inlay deeper,” he added. “The take-home message for us was that we began implanting the inlays at 250 μm or deeper.”
Deeper implantation was not a complete surprise, he continued.
The inlay was initially placed under a standard LASIK flap, but the shallow implantation tended to produce dryness and other problems. Surgeons began implanting the inlay deeper, eventually moving to a pocket procedure by the time the pivotal FDA study was designed and approved. At least one other inlay is routinely implanted at 300 μm.
“When we started to look at the comparative data, it is very clear that patients with deeper implantation of the Kamra had better clinical results,” Dr. Hoopes said.