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Intracorneal inlay improves near, intermediate vision, preserves distance
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A new intracorneal inlay, Kamra, developed by AcuFocus to reverse the effects of presbyopia and restore near and intermediate vision, is a presbyopia treatment that does not sacrifice distance vision, according to clinicians experienced with the device.
“The inlay design, being a fixed small aperture, is based on the principle behind an F-stop on a camera. When the lens aperture is very small, objects at various distances come into focus simultaneously,” Sondra Black, OD, director of clinical operations at Crystal Clear Vision in Canada, said in an interview with Primary Care Optometry News. “It allows the patient to not only be able to read but also improves their intermediate without sacrificing their distance vision. And although at near it is a monocular procedure, unlike monovision it still allows the patient to have binocularity at distance.”
The inlay is an opaque circular micro-disc with a 1.6-mm central opening and 8,400 high-precision laser-created micro-perforations along the surface that help maintain a healthy cornea, according to the AcuFocus website.
“It uses small-aperture optics to increase the patient’s depth of focus,” Black said. “Essentially, this is the pinhole effect.”
The inlay is made of polyvinylidene fluoride, which is resilient, strong and UV resistant, Eric T. Brooker, OD, medical director of the Advanced Vision Institute in Las Vegas, told attendees at the Optometric Council on Refractive Technology annual symposium. The symposium was held just prior to Academy 2012 in Phoenix.
“The 8,400 microperforations are [cut] in a pseudo-random pattern,” he said. “The engineers were able to find a pattern that would both provide for nutrient flow through the inlay and minimize night vision complaints.”
Clinical effects of this inlay on diagnostic examinations are minimal, he said. Gonioscopies, fundus photography and optical coherence tomography imaging are easily performed through the inlay.
This image shows the Kamra inlay implanted in the eye of Jeff Machat, MD.
Image: Black S
“And they’re removable,” Brooker added. “The removal rate globally is approximately 1.3%, which is lower than most LASIK enhancement rates.”
“This is important when considering the safety aspect,” Black said. “If the patient is truly unhappy, it can be removed, and the eye will go back to its original pre-implantation state.”
The inlay is approved in 46 countries and was approved in Canada in September 2012, according to Brooker.
“I haven’t seen so much excitement from ophthalmology since LASIK,” he said.
The Kamra inlay is not currently approved for use in the U.S.
Kamra surgery
The inlay is designed to treat emmetropic presbyopes; however, the patient can be corrected to emmetropia in various ways, Black said in the interview.
The inlay can be implanted in a variety of patients, including patients who are naturally emmetropic, in patients who have already had LASIK or PRK and in IOL patients who already have a monofocal implant. The Kamra inlay can also be implanted simultaneously with LASIK, Black said.
Different procedures are specific to each type of patient.
Pocket Emmetropic Kamra (PEK) is performed on naturally emmetropic patients and consists of creating a 200-micron pocket with a femtosecond laser in the nondominant eye where the inlay is implanted, according to Black.
“By the end of the healing process, patients should be J1 to J2,” she said. “I have some patients that are J1+.”
Combined LASIK Kamra (CLK) is performed the same way, except the inlay implantation is performed simultaneously with LASIK.
“A 200-micron flap is created on the nondominant eye, the LASIK is performed and then the inlay is placed under the flap,” Black said.
Post-LASIK Kamra (PLK) is for patients who have had previous LASIK and are now presbyopic.
“The femtosecond laser creates a pocket 100 microns below the existing flap on the nondominant eye, and the inlay is inserted,” she said.
The Planned LASIK Kamra (PLK2) option entails first creating a 100-micron flap and performing the LASIK procedure. One month later the patient returns, and a 200-micron pocket is created in the nondominant eye and the inlay is inserted, Black said.
“Counsel them that mild blur at distance and loss of reading will be temporary,” she said.
In cases where femtosecond lasers were used to create a pocket for the Kamra inlay, patient satisfaction was higher when they had a small amount of residual myopia, Brooker said during the symposium.
Postop protocol
“The postop exam schedule is similar to any other refractive procedure — 1 day, 1 week and then 1, 3, 6 and 12 months,” Steven H. Linn, OD, a researcher involved in the AcuFocus clinical trials, said during the symposium. “In postop testing, refraction is important. Slit lamp exams are important to look at eye health. Patients will be on steroids for a while, so always follow IOP. Watch out for dry eye, too, because that can also influence outcomes.”
The AcuFocus medical advisory board has recommended a postop regimen of a fluoroquinolone, artificial tears and a strong steroid for the first week. The switch is made to a weaker steroid for 3 months, tapering from four times a day to three times a day then twice a day in the third month, Linn said.
“Recovery was not like LASIK. We needed to do aggressive treatment because of the healing response. If there was poor management, it could result in an unwanted wound healing response,” he said.
Ocular surface management should be optimized with strong use of preservative-free artificial tears, punctal plugs in all patients, supplementation with omega-3 and possibly Restasis (cyclosporine A 0.05%, Allergan).
“In slit lamp exams, look for areas of irregularity, damage to the inlay, diffuse lamellar keratitis, epithelial ingrowth, stromal haze and striae and always assess refractive changes. Sometimes people can become hyperopic in the healing phase as part of the healing response,” Linn said.
Most patients can resume normal activities 1 day postop and are stable at 1 month, he said.
Results have generally been good, but expect that there may be a need for readers for tiny print, dim light situations or extended periods of near work, Linn said.
“It’s important that patients’ expectations are realistic,” Black said in the interview. “They must understand that this is a surgery and there is a healing process. Some patients will see a jump in their vision the day after surgery, but for others it may take a few weeks to a few months to get the desired effect.”
Determining candidates
“As a general rule, if the patient is not a candidate for LASIK due to medical or ocular reasons, then the patient is not a good candidate for Kamra,” Black said in the interview.
This means patients are not good candidates for the procedure if they have systemic conditions such as auto-immune conditions, keratoconus, uncontrolled dry eye, age-related macular degeneration, amblyopia or strabismus, among others, Black said.
“We are looking for patients that find the need for reading glasses a disability. They have to be motivated and willing to accept the recovery process,” she said.
“With global information being so readily available, patients will come into your offices asking about the procedure that is now being performed in Canada,” Black told PCON. “If ODs want additional information or guidance, they can certainly reach out to us.
“This is going to be as big as, if not bigger than, LASIK was in the early days, and it’s going to change the way optometrists talk to their presbyopes about surgical options,” she said. – by Daniel R. Morgan
For more information:
Eric T. Brooker, OD, can be reached at Advanced Vision Institute, Las Vegas; (702) 503-3591; drbrooker@advancedvisioninstitute.net.
Steven H. Linn, OD, can be reached at Hoopes Vision, Draper, Utah; (801) 568-0200; steve@hoopesvision.com.
Disclosures: Black and Linn have no relevant financial interests to disclose. Brooker is a consultant for AcuFocus Inc.