Clinical Update REFRACTIVE SURGERY The Kamra Corneal Inlay in the Clinic by leslie burling-phillips, contributing writer interviewing wayne crewe-brown, mb, chb, mmed, sheldon herzig, md, frcsc, and david g. kent, md, mbchb, franzco, fracs ommercially available in vantage of the inlay is that the distance Kamra in Place Europe, the Asia-Pacific vision compromise in the reading eye region, South America, and is significantly less than what is experi- the Middle East prior to FDA enced with monovision, where the pa- approval in April this year, tient must tolerate and accommodate Cthe Kamra corneal inlay (AcuFocus) for the distance vision blur created in now offers U.S. ophthalmologists an the reading eye,” said David G. Kent, alternative treatment for presbyopia. MD, MBChB, FRANZCO, FRACS, at According to the FDA, the device is the Fendalton Eye Clinic in Christ- indicated for phakic presbyopes be- church, New Zealand. tween the ages of 45 and 60 who do Studies. Long-term study results in- not require glasses or contact lenses for dicate that the inlay is a safe, effective, distance vision but have a near vision and reversible treatment for presby- correction need of +1.00 D to +2.50 D. opia. Patients in one study gained 2 or Three ophthalmologists—from New more lines of uncorrected near visual Zealand, Canada, and England—share acuity and did not show significant their experiences with the Kamra cor- loss in distance vision when evalu- neal inlay. ated 4 years after inlay implantation.1 The intrastromal pocket, created with Reading performance is also positively a pocket software–approved femtosec- How the Inlay Works affected. Significant improvements ond laser, should be between 200 and The Kamra is a disk, 3.8 mm in diam- were reported after 12 months, with 250 μm deep. eter, made of polyvinylidene fluoride improvement continuing for up to 24 and carbon with a small opening (1.6 months, though at a slower pace.2 tients are chosen carefully and they mm in diameter) in the center. The de- participate in a full informed consent sign is based on the principle of small- Candidates discussion, most of them will be satis- aperture optics: The inlay is positioned While presbyopes typically range in fied with their postoperative vision, over the central zone of the cornea— age between 40 and 60, said Dr. Kent, said Sheldon Herzig, MD, FRCSC, of directly in front of the pupil—in a pa- not all are ideal candidates for the Kam- The Herzig Eye Institute in Toronto, tient’s nondominant eye. The exterior ra corneal inlay. For example, “there Canada. He noted that he has achieved opaque ring blocks the unfocused pe- are certain circumstances when it is the best results in: 1) patients with a ripheral light rays, while letting in the more applicable to perform a refractive spherical refraction between –0.50 and focused central rays through the open- lens exchange with multifocal intra- –0.75 D, 2) patients who do not have ing, which increases depth of focus ocular lenses. This is more common significant dry eye, and 3) patients and improves near vision. This effect among patients at the upper end of the who are free of ocular surface disease. is well known to photographers, who presbyopic age range because it is likely Look for clues. “Pay close attention gain depth of focus by decreasing the that their lenses are aging, showing to tear film quality, the condition of size of the aperture on the camera lens. signs of cataract, and an inlay is not the cornea, and a patient’s eyelids dur- Theoretically, “the Kamra corneal the optimal solution,” he said. ing your assessment,” said Dr. Kent, inlay could be considered a modified Above all, patient selection and explaining that patients with meibo- 3 christopher rapuano, j. md form of monovision. The primary ad- counseling are important. When pa- mian gland dysfunction and blepha- eyenet 53 Refractive Surgery ritis do not do as well with the Kamra Surgical Tips corneal inlay because of poor-quality tear film. These patients are much Dr. Kent of New Zealand offered his tips for successful inlay placement. (Note more likely to develop postoperative that in the United States, the physician labeling specifically warns that safety and dry eye, he said. “Treat and resolve effectiveness of Kamra implantation in conjunction with or after LASIK or other these conditions to a satisfactory level refractive procedures is “unknown.”) prior to embarking on inlay use.” • If LASIK is needed, aim for a target refraction of –0.75 D. Wait 4 weeks Does pupil size matter? Pupil size after LASIK before placing the inlay. “Some surgeons try to do it all in one day— could be a factor in patient selection that’s a very advanced procedure—it’s highly technically difficult,” he said. (Dr. for the Kamra corneal inlay, albeit Crewe-Brown waits from a few days to a few weeks between procedures.) an uncommon factor, said Wayne • Measure the thickness of the flap with an anterior segment OCT to ensure Crewe-Brown, MB, ChB, MMed. He that the flap is sufficiently thin—and that there is enough distance between the noted that current protocol suggests a LASIK flap bed interface and the pocket, where the inlay is placed. “That’s im- maximum pupil size of 6 mm because portant because you don’t want to find that, when you create the pocket with the large pupils could affect the inlay’s femtosecond laser, gasses are escaping into the flap bed interface. You need roughly performance due to its fixed diameter 100 μm between the flap bed interface and where the inlay is going,” he said. of 3.8 mm. As the pupil increases to • When creating the pocket, it is essential that you use a femtosecond laser sizes of 4 mm or larger, light rays are with the proper pocket creation software. Target depth for the pocket is between able to pass around the inlay, decreas- 200 and 250 μm. ing reading performance. “Although • It is important to achieve a smooth interface in the pocket. Any roughness this is something to take into account, will increase the likelihood of haze around the inlay and hyperopic shifts. we see very few middle-aged patients • Centration of the inlay is important. Center the inlay in the pocket with one with large pupils, and this has not been smooth motion, using minimal manipulation. Optimal placement is approximately a hindrance.” Dr. Crewe-Brown is head halfway between the center of the pupil and the first Purkinje light reflexes. of Crewe-Brown Vision in London. • Use the lowest energy setting that will create a pocket that allows for easy Set reasonable expectations. opening. Too much energy will create an irregular pocket, which can negatively “Patients with very high near-vision affect a patient’s response to the inlay. demands—a watchmaker or contract attorney who reads copious amounts of documents, for example—may not Although the procedure is relatively rate of approximately 5%, found that be the ideal patient for this procedure. simple, these patients will require con- was not always the case. “Some pa- Unless these patients recognize that siderably more postoperative follow-up tients had blurred distance vision with they may still need reading glasses than PRK or LASIK patients, said Dr. occasional night vision issues, and on certain occasions, they may not Crewe-Brown. Follow-up is typically their best-corrected vision was reduced be happy with the outcome,” said Dr. scheduled at week 1 and months 1, 3, in the treated eye.” Crewe-Brown, who also described 6, and 12; but patients with complica- Although hyperopic shift was a another challenging group of patients: tions should be monitored even more more frequent problem among patients “We are dealing with a population, closely, he said. who underwent earlier forms of the particularly females, who inherently Most patients begin to have im- procedure (which used a thick flap as have dry eyes. This condition can be proved near vision within days or opposed to an intrastromal pocket) exacerbated postoperatively. It gener- weeks of inlay placement, said Dr. and now occurs only occasionally, it ally resolves with treatment and time Kent. Corneal haze associated with remains a complication associated but should be carefully managed.” inlay implantation generally subsides with inlay use, said Dr. Crewe-Brown. spontaneously with time, but other In the more than 800 inlays that he The Procedure complications such as dry eye and hy- has implanted, 3 or 4 required removal The Kamra corneal inlay is a good op- peropic shift require additional patient due to hyperopic shifts. “Sometimes a tion when treating the right subpopu- management, he noted. patient does well for several months. lation of presbyopic patients, and it of- Suddenly their vision drops off, and re- fers a number of surgical benefits, said Removal Scenarios fraction reveals the change. In general, Dr. Crewe-Brown. He noted that the Despite comprehensive preoperative this is resolved with a short course of inlay portion of the procedure takes screening, the inlay is just not a good steroid drops,” he said. However, he 15 minutes, is minimally invasive, and “fit” for 5% to 10% of patients, said noted that if a steroid regimen is not can be performed in the surgical suite Dr. Herzig. Although AcuFocus states successful after 3 attempts, removal with a femtosecond laser; it requires that quality of distance vision is not af- should be considered. the acquisition of a few devices and fected significantly by the Kamra inlay, Cataract surgery. When it comes pocket-creating software. Dr.