The small-aperture KAMRA inlay, a surgical option for the treatment of presbyopia
The KAMRA inlay (left) compared to a contact lens (right). The KAMRA inlay is 6 microns thick, 3.8mm in diameter, with a 1.6mm aperture.
Source (all): Daniel Durrie, MD
Strategies for predicting success
The two corneal inlays now available in the U.S. are making inroads at many practitioners’ offices. But these are not for everyone. Here are some testing strategies that will help practitioners best predict who is likely to thrive with the procedure.
Attaining success from the start is paramount, according to Daniel Durrie, MD, clinical professor of ophthalmology, Kansas Medical Center, and founder, Durrie Vision, Overland Park, Kansas. “When you’re introducing a new procedure into your practice, you want your first 10 to 20 cases to go extremely well because your staff is looking over your shoulder and your partners are saying, ‘Is it worthwhile getting involved in this?’” Dr. Durrie said. “You want to pick your patients with the best chance of success right from the beginning.”
Both the KAMRA (AcuFocus, Irvine, California) and the Raindrop (ReVision Optics, Lake Forest, California) have been through the U.S. Food and Drug Administration (FDA) approval process, Dr. Durrie said, adding that there was important information gleaned from the data. “We know from the clinical data that the people who are slightly hyperopic are the best candidates for the Raindrop inlay, and the people who are slightly myopic in their non-dominant eye are the best candidates for the KAMRA inlay,” Dr. Durrie said. “So we have a differentiation right from the beginning depending on where the patient’s refractive status is.” If patients have had previous LASIK or are planning on having LASIK in combination with an inlay, practitioners should carefully measure them and adjust the refractive error to make it ideal for the inlay, he said. If they’re going to undergo combination surgery, they need to be an excellent candidate for the procedures.
Likewise, Gary Foster, MD, medical director, Eye Laser Center of Northern Colorado, Fort Collins, Colorado, stressed the importance of testing patients and educating them to ensure that they are well-suited for an inlay. “I think proper patient selection and education is paramount with the inlay and similar to the education required with a multiple focus lens,” Dr. Foster said. With any of the available inlays, there are significant benefits but also certain compromises that must be accepted in order to receive those benefits, he pointed out, adding that it’s important that patients clearly understand the tradeoffs so they can make an informed decision. “That increases the chances that they’ll be happy with the result that they receive afterward,” Dr. Foster said.
One of the most important pieces of testing and education for the inlays, which are traditionally placed monocularly, is to find out whether the patient can read with one eye. “Some are wired in a fashion where they aren’t able to accept that,” Dr. Foster said, adding that if the inlay is placed in the non-dominant eye and patients can only accept reading with their dominant one, they may not feel like they have functional reading. “That’s something we can test for ahead of time by showing them reading with monovision,” he said. “With the inlay, they still have distance vision in both eyes so it’s easier for them to accept that kind of monovision, but they need to be able to read with just one eye.”
Dr. Foster stressed the importance of discussing with patients the potential night symptomatology with the inlay such as glare and halos. Physicians should also ensure that they don’t have an occupation that precludes any form of monovision. “I think the main issue is finding a way to demonstrate to them as closely as you can what their vision would be like,” Dr. Foster said. For example, the pinhole process makes reading very accessible and comfortable, but the letters aren’t in a perfect focus.
As part of the education process, Dr. Durrie recommends talking to patients about dysfunctional lens syndrome, which can be clearer to them than the term presbyopia. The term dysfunctional lens syndrome has become popular because it pegs the lens as the problem, he explained. “I’ve always found that it’s worthwhile to tell patients about the whole process: In their 40s the lens is going to be clear and colorless, but in stage 1 of dysfunctional lens syndrome, the lens loses its elasticity and the muscles can’t bend it anymore and they start picking up reading glasses,” Dr. Durrie said. “Stage 2 is in their 50s and 60s, and that’s when the lens starts turning yellow and a bit hazy, and at that point night vision is not as good and they need more light to read. When they reach stage 3, usually in their 70s and 80s, they must contend with a cataract.”
Dr. Foster concurs that dysfunctional lens syndrome is important. This, he said, comes into play in deciding the best way to solve patients’ problems. “I use the HD Analyzer [Visiometrics, Barcelona, Spain] to help me differentiate which stage of dysfunctional lens syndrome they’re in,” Dr. Foster said. “In young patients who have a fully functioning lens, we usually will use LASIK to help them solve their visual issues,” he said. “Once they move into the age where presbyopia is an issue, we will often use a combination of LASIK with the KAMRA inlay to give them both distance vision and reading.” However, as they start having more advanced amounts of lens dysfunction, it makes sense to solve their issues with a lens-based surgery, he has found.
Likewise, Dr. Durrie said that the inlays work best in stage 1 when the lens is still clear. “As soon as you get to stage 2, when they’re starting to get some scatter of light, they’re starting to get loss of contrast sensitivity, and the corneal inlays don’t work as well,” he said, adding that while you can still do them, you should alert patients that they’re probably going to need lens replacement surgery.
He also tests patients with the HD Analyzer, which shows how much light scatter there is. “We find that we use it on every patient,” Dr. Durrie said, adding that even younger patients who should have perfect results occasionally have scatter, which may point to keratoconus, dry eye, or some type of corneal lens opacity.
Dr. Durrie also examines inlay patients’ OCT to make sure that the retina is intact. He begins the workup with the OCT and then moves to the HD analyzer. “If there is scatter on the HD Analyzer, then you need to look and see where that is coming from,” he said. “Is it coming from the tear film, cornea, or the lens?” Asteroid hyalosis or bad floaters can cause such scatter, he continued. If there is scatter, then he looks further at the slit lamp and also may examine the patient with the Pentacam (Oculus, Arlington, Washington) or Galilei (Ziemer Ophthalmic Systems, Port, Switzerland) and pinpoint whether this is coming from the lens.
In addition to the HD Analyzer, physicians can get information from other devices such as the Nidek OPD (Nidek, Gamagori, Japan), iTrace (Tracey Technologies, Houston), the Pentacam, and the Galilei, as well as from slit lamp photographs, Dr. Durrie noted.
Dr. Durrie recommended evaluating the tear film. “Corneal inlays require a good ocular surface, so we’ve recently started using the LipiView/LipiScan [TearScience, Morrisville, North Carolina] on all of our patients to look at their meibomian gland structure very early in the exam,” he said. “We would not put an inlay in someone who had poor meibomian gland structure or function because with both of the inlays we’re expecting the very center of the visual axis not to have light scatter.” He finds that for those with dry eyes in general and evaporative dry eyes in particular, the inlay doesn’t work as well. “We would rather identify that and treat it ahead of time to the point where it’s more functional before they go on to any type of surgery,” he said.
Likewise, Dr. Foster thinks that the health of the tear film has a significant impact on the outcome for corneal inlay patients, so analysis of the tear film is essential preoperatively. “If it’s less than ideal, we would postpone surgery until medical therapy restores a great tear film, then we would make the decision about whether they’re a good candidate for the inlay based on how difficult it was to achieve and sustain that.” He relies on a good history and a slit lamp examination is essential to help determine that. “The HD Analyzer is helpful as it measures changes in light scatter during sustained non-blink periods. If the light scatter escalates in between blinks, it demonstrates a poor quality tear film,” Dr. Foster said, adding that the LipiView can also be helpful if the meibomian glands are in question.
It’s important to test for ideal inlay placement. For that, Dr. Durrie relies on software built into the HD Analyzer known as the AcuTarget HD. “It gives us the inlay centration and tells us that ahead of time,” he said. “Postoperatively it’s very helpful because you can measure whether the inlay is in the correct place.” If patients have had a corneal inlay and after surgery are still not functioning at their best, determining if the inlay is in the right place can help, Dr. Durrie said.
Overall, Dr. Foster advised using the same wisdom and judgment as you would in selecting a multifocus lens patient. “Most patients are happy rather quickly, and there are a few that aren’t, but as you help them with their tear film management and ongoing healing, they achieve happiness.” Then there is a small percentage that don’t get the reading they desired, and these patients are going to require extra care to get them through that process, he concluded.
Editors’ note: Dr. Foster has financial interests with AcuFocus. Dr. Durrie has financial interests with AcuFocus, Alcon (Fort Worth, Texas), Abbott Medical Optics (Abbott Park, Illinois), and Visiometrics.