Combining LASIK, corneal inlays hits refractive ‘sweet spot’ for many patients
Refractive lens exchange is a viable and very reasonable option to offer patients across the various ranges. Corneal inlays, when implanted at an appropriately deep corneal location, provide good near vision, minimizing the impact on uncorrected distance vision.
Reviewed by William F. Wiley, MD
Numerous advances have been made in refractive surgery technology that provide patients with numerous options from which to choose.
“Among the options, corneal inlays are one of the newest advances that we have seen,” according to William F. Wiley, MD, medical director, Cleveland Eye Clinic, Brecksville, OH.
The most recent developments in this market include the approval of the Kamra corneal inlay technology (AcuFocus) in mid-2015; the Raindrop Near Vision Inlay (ReVision Optics), which was approved in 2016 and recently pulled from the market; and the Flexivue Microlens (Presbia), for which approval is pending.
Developing market base
One of the biggest problems with corneal inlays in a refractive practice is developing the patient base for the technology. In a typical refractive surgery practice, Dr. Wiley pointed out, most patients who seek out a refractive procedure are those with myopia and hyperopia who represent the smaller part of the bell-shaped curve of possible refractive clients.
“The traditional market audience for corneal inlays lies in the meat of that bell-shaped curve and represents over 100 million patients with presbyopia,” he said. “The reality is that it is hard to get those patients into the office.”
The target market for corneal inlays includes patients between 45 and 60 years old with a prescription ranging from +0.5 to –0.75 D who have had an eye examination within the previous year, he said.
“The issue with the presbyopic patient base is that the bulk of the target audience is not coming into our offices,” Dr. Wiley said. “They are solving their presbyopic problem with over-the-counter readers.”
The patients who are seeking refractive surgery can now be offered a combination approach to meet their visual needs. The typical patient considering a refractive procedure is a 50-year-old with a bilateral refractive error of –4 D.
“This is the group that is motivated to become spectacle independent for distance and near vision,” he commented.
Dr. Wiley can now satisfy that patient’s goal for distance and near vision by combining inlays with a refractive surgery. Typically, he explained, the distance eye is targeted for plano and the non-dominant eye is left with about –0.75 D of myopia. During the same surgery for LASIK, the corneal inlay is implanted into a pocket that is under the LASIK flap.
“The excimer laser is the perfect tool to prepare the eye for the ultimate refraction,” he said.
Following surgery patients have 20/20 distance vision and functional near vision that continues to improve over time.
“These results let us increase the ‘wow’ effect on the first postoperative day,” Dr. Wiley said.
The key to building the corneal inlay patient base is the recognition that almost every presbyopic patient is a candidate for corneal inlays. LASIK is the perfect tool to bring those patients to the refractive sweet spot, he pointed out. When implanting the aperture inlay, that refractive sweet spot is –0.75 to –1 D. Dr. Wiley explained that functionally the intermediate vision interacts with the aperture optic to extend the focus to both distance and near vision.
Making the adjustment to that proper target is important. Dr. Wiley offered the analogy that implanting a corneal inlay without adjusting to the appropriate target is comparable to implanting a premium cataract surgery without addressing the astigmatism.
The first is that implanting inlays is not the same as monovision. Dr. Wiley demonstrated that monovision has a very narrow depth of focus, while the Kamra inlay provides a wide depth of focus and sharper vision. Another consideration is that monovision is a static solution for a dynamic problem, he noted, in that presbyopia continues to progress over time. In contrast, inlays are a dynamic solution to presbyopia progression. Another fallacy is that inlays are intended to serve a niche market.
However, analysis of his practice showed that the corneal inlay is the choice of patients seeking to correct their presbyopia. Another myth is that all inlays cause haze. This concern arose because of problems that developed specifically with the Raindrop Near Vision Inlay; by 5 years postoperatively about 75% of patients developed haze at some point with about 20% of patients having the inlay removed. The FDA issued a warning letter recommending close follow-up of patients who received this implant as well as close follow-up after the device is removed.
Even though the risks are low with aperture inlays, because of the potential risks, it is important to have proper informed consent with all corneal inlays and care should be taken to use the most up to date techniques and technologies. Location is everything. Dr. Wiley explained that haze may develop because of shallow implantation of shape changing inlays. In contrast, the aperture inlay is implanted deeper, which results in a much lower incidence of haze. In his hands, less than 1% of 353 Karma implants were removed because of haze, compared with 40% of 15 Raindrop inlays.
The keys to success
Besides the target of –0.75 D of myopia in the inlay eye, preoperatively, the ocular surface should be optimized preoperatively. The depth of the inlay is clearly the paramount factor. The pocket for the inlay should be at a depth of 250 to 300 microns, with 4 x 4 or less spot/line separation settings on the femtosecond laser. Dr. Wiley advised using balanced saline solution when dissecting the pocket.
Data provided by Clearsight LASIK indicated that patients achieve three lines of uncorrected near vision with the Kamra implant with no effect on the uncorrected distance vision.
“Inlays have a place in the surgical correction of presbyopia and in refractive surgery practices,” Dr. Wiley said. “Significant improvements have been made in the surgical techniques, patient selection and perioperative patient management that have resulted into successful integration of inlays into our practice, which can be translated to other refractive surgery practices.”
William F. Wiley, MD
Dr. Wiley is a consultant to CorneaGen and an investigator for Presbia.