Side view of an inlay as a diamond blade corneal incision is created
Microscope view of KAMRA inlay in an eye with a posterior subcapsular cataract
Cataract removed with phaco under the inlay
View of posterior subcapsular cataract shows how it interferes with patient vision.
Source (all): Kevin Waltz, MD
Surgeons’ experience with corneal inlays have shown which patients can benefit and how the devices interact with other treatments
The emerging presbyopia treatment of corneal inlays expands surgeons’ options, but the technology can affect other vision treatments.
Corneal inlays are one of a growing number of surgical options to address the deteriorating function of the crystalline lens over time, known as dysfunctional lens syndrome (DLS).
LASIK monovision is the traditional treatment for many patients with stage 1 DLS, which for many patients is not only presbyopia but an uncoupling of the offset of spherical aberration between their lens and cornea. Jay Pepose, MD, PhD, director, Pepose Vision Institute, and professor of clinical ophthalmology, Washington University School of Medicine, St. Louis, considers LASIK with blended vision for suitable candidates after assessing corneal topography, pachymetry, and the ocular surface.
Stage 1 patients also can now be treated with the KAMRA inlay (AcuFocus, Irvine, California), which is a small aperture implant placed in a lamellar pocket. The device works best implanted monocularly in –0.75 D eyes, whether with natural vision or after LASIK, Dr. Pepose said.
In comparison, the Raindrop inlay (ReVision Optics, Lake Forest, California), which is placed directly under a LASIK-type flap, can help patients with good distance vision and up to 1 D of hyperopia.
Among stage 1 patients considering corneal inlays, William Wiley, MD, medical director, Cleveland Eye Clinic, Ohio, may try a multifocal or monovision contact lens, which provides similar optics to a Raindrop inlay.
“That simulates nicely what Raindrop vision is,” Dr. Wiley said. “Alternatively, we can demonstrate an aperture optic with a pinhole occluder in the office to simulate the optics of a KAMRA corneal inlay.”
Dr. Wiley discusses advantages and disadvantages of each option for patients, some of which depends on their baseline prescription. More myopic patients—in the range of –0.5 D or –0.75 D—tend to do well with a KAMRA inlay, Dr. Wiley said.
“It seems that the KAMRA with aperture vision optics, takes good intermediate vision and extends the depth of focus to both distance and near,” Dr. Wiley said. “So patients starting with mild myopia do well with the KAMRA inlay.”
If the patient is a low hyperope, he or she tends to set up better for a Raindrop. The “sweet spot” is somewhere between +0.5 D and +0.75 D, Dr. Wiley said. The inlay works by steepening the cornea centrally, which not only treats some of the hyperopia but also brings in the near vision.
“So often we lean toward the Raindrop in the low hyperopes,” Dr. Wiley said.
As discussed, the prime base range of corneal inlays is between -.75 (KAMRA) and +.75 (Raindrop). Presbyopic patients with baseline prescriptions beyond these sweet spots may benefit from combined LASIK and corneal inlay. As such, LASIK can be used to bring the baseline position into the ideal range of performance for corneal inlays, Dr. Wiley said.
Kevin Waltz, MD, president, Ophthalmic Research Consultants, said it’s important to recognize inlay patients are usually between 45 and 55 and have some residual accommodation—just not enough.
“We’re augmenting it, and the augmentation will last for a period of time, just like when you do monovision,” Dr. Waltz said. “If you get monovision at 50, often you’ll get about 1 D of myopia to help with the loss of accommodation. It’s something that works for a period of time and works pretty well but ultimately you will need something else.”
Dr. Waltz noted that the greater the patient’s presbyopia, the less well corneal inlays work.
Dr. Wiley leans toward a clear lens exchange in patients in their 40s with higher prescriptions, such as +4 D or +5 D. In such patients he uses an extended depth of focus lens, often in the dominant eye. After assessing the visual function in the first eye, he matches it with either a Symfony lens (Abbott Medical Optics, Abbott Park, Illinois) or a traditional multifocal in the second eye.
“We find that the extended depth of focus lens gives great intermediate and distance vision but sometimes does not deliver the near vision that patients are looking for,” Dr. Wiley said. “So in the second eye we consider doing more of a traditional multifocal to bring in better near vision.”
Dr. Waltz said some surgeons follow the “rule of eight,” in which they consider clear lens removal reasonable in patients who score eight or more in a grading system, which includes one point for every decade of life and one point for every diopter of hyperopia.
“That gives an upper border for when it is time to think about lens surgery instead of an inlay,” Dr. Waltz said.
Stages 2 and 3
Corneal inlays drop off Dr. Pepose’s algorithm among eyes in stage 2 DLS, which are those with moderate scatter.
“I consider monovision or blended vision LASIK, with an explanation that this will not end the aging process and eventually cataract surgery will be required,” Dr. Pepose said.
Additionally, stage 2 patients could consider cataract IOLs options and possibly benefit from a premium IOL, he said.
For stage 3 DLS, which includes significant scatter, cataract surgery is indicated, and Dr. Pepose assesses the patient’s vocation and avocation, biometry, angle kappa, corneal wavefront, macular function, and ocular surface. Additionally, Dr. Pepose discusses the best IOL option or combination for each patient.
The older the patient (and thus, the increased likelihood of cataract formation), the more Dr. Wiley leans toward a lens procedure instead of a corneal procedure.
“If their lens is showing scatter, like an AcuTarget [AcuFocus] showing that they already having optical quality decrease in addition to the presbyopia demonstrated by the objective measure of the device, then we will lean more toward a lens procedure,” Dr. Wiley said. “But usually it is dictated by age. So the older they are, the more we will lean toward lens replacement, rather than corneal surgery.”
Dr. Waltz noted that when the natural lens is replaced, it improves the function of the KAMRA, and he anticipates the same result with the Raindrop.
“One of the nice things about treating [DLS] with this is that you pay for it once, you get it inserted once, and one day when you have cataracts you get a reinvigoration of your benefit, which is a nice treat,” Dr. Waltz said.
Dr. Waltz said he has performed several cataract surgeries with an inlay in position.
“You have to get over your concern that you cannot see the entire field,” Dr. Waltz said. “It turns out that you are stroking with your phaco handpiece through these blacked out zones, but it doesn’t harm anything, it doesn’t slow down your surgery, and it’s very doable.”
Visualizations with an inlay can come from rotating the globe to look at different parts around the inlay, Dr. Waltz said.
An important note is that femtosecond cataract surgery should not be performed through an inlay, the surgeons said. The black KAMRA inlay is highly absorbent of infrared energy, heats up, and harms the cornea with the heat. Similarly, a Raindrop will distort the layer of the cornea the laser will cut.
“For those two reasons you cannot use femtosecond lasers with either of the current corneal inlays in place,” Dr. Waltz said.
Another important note is that although corneal surgery can make cataract surgery calculations more difficult and the outcome less predictable, inlays do not complicate calculations, Dr. Waltz said.
Dr. Waltz said calculations with the KAMRA inlay should use the center point on the topographer—not manual keratometry or simulating tables—to account for changes in the keratometry.
Editors’ note: Dr. Wiley has financial interests with AcuFocus, ReVision Optics, and Abbott Medical Optics. Dr. Pepose has financial interests with AcuFocus. Dr. Waltz has financial interests with AcuFocus and Abbott Medical Optics.