More than 1.2 million cases of LASIK surgery have been performed at the Shinagawa LASIK Center since it opened in Japan in 2004, with approximately 15% of these patients seeking some form of presbyopia correction. From among the variety of surgical treatments currently available, my current preference for patients between 40 and 60 years old, without cataract, is implantation of a corneal inlay; for patients more than 60 years old or between 40 and 60 years old with cataract, it is lens-based presbyopia correction.
Since 2009, our clinic has been implanting the Kamra small-aperture corneal inlay (AcuFocus, Inc.; Figure 1) for most presbyopic patients who do not have a cataract. The Kamra inlay is commercially available in 49 countries, and nearly 20,000 inlays have been implanted worldwide to date. It allows only central collinear light to reach the retina through its central 1.6-mm aperture. As a result, patients’ depth of focus is expanded, improving near and intermediate vision with minimal impact on distance vision (Figure 2). The inlay is implanted into the patient’s nondominant eye, and, if necessary, the dominant eye is treated with LASIK for distance vision.
LASIK PLUS KAMRA: CLK AND PLK
Because our clinic is widely known for providing LASIK surgery, approximately 90% of the presbyopic patients we see have some degree of refractive error requiring treatment. For patients without cataract, combined LASIK and Kamra implantation (CLK) allows correction of both refractive error and presbyopia simultaneously. In a CLK procedure, a 200-μm flap is created in the implanted eye using a femtosecond laser, refractive correction is performed, the flap is replaced, and the stromal bed is irrigated. With the inlay loaded into forceps, the LASIK flap is lifted again, and the inlay is placed on the corneal bed. The surgery is rather easy for refractive surgeons and does not take more than 10 minutes. For a video demonstration of the CLK procedure, visit eyetube.net?v=gohom.
Based on more than 3,000 cases of CLK performed in our clinic, postoperatively patients may rarely experience slight dry eye and a slight refractive shift, and this may occasionally affect visual acuity. One of the reasons for this is the 200-μm flap dissection, which severs corneal nerve-fiber bundles. This can affect tear-film stability, corneal sensitivity and sensation, and the blink reflex, all of which can influence outcomes and result in dry eye. 1-3
Although the effects of dry eye are mitigated with time, a punctal plug can be implanted and dry eye therapy initiated postoperatively to relieve symptoms.
Our clinic also sees patients who have previously had LASIK and are now seeking treatment for presbyopia. Post-LASIK Kamra (PLK) is an excellent treatment option to consider for these patients. In this procedure, a corneal pocket is created with a femtosecond laser in the nondominant eye at least 200 μm deep in the cornea and with 100 μm between the inlay pocket and the LASIK interface (Figure 3). For a video demonstration of the PLK procedure, visit eyetube.net?v=rizoh.
We have learned that, after PLK, patients experience fewer dry eye symptoms than after CLK procedures, which may be due to fewer peripheral corneal nerves being altered during pocket creation. We have also found that PLK patients have better quality of vision postoperatively than CLK patients, as demonstrated by improved Optical Scatter Index (OSI) scores. Although the reason for the difference in OSI is not fully understood, it is most likely due to the LASIK portion of the procedure being performed more shallowly in the cornea, where the collagen fibers are more densely packed and femtosecond and excimer lasers have been optimized to perform. For these reasons, our clinic has moved almost exclusively to PLK procedures for our inlay patients. 4,5
ACHIEVING BEST RESULTS
To achieve the best results and fastest visual recovery, surgeons should minimize surgical manipulation to minimize postoperative edema. I recommend entering the pocket interface a maximum of two times. Postoperatively, antibiotics, steroids, and aggressive dry eye therapy should be used to help modulate the healing response. It is also important to remember that all new techniques have a learning curve. Excellent results are possible from the beginning, but agility with the procedure improves with practice.
Overall, we have experienced excellent outcomes with the Kamra inlay. On average, patients achieve J2 near UCVA and maintain a mean distance UCVA of 20/20. 4,5 Additionally, contrast sensitivity remains within normal limits, and more than 90% of patients are functionally independent from glasses. The Kamra inlay has fewer risks than other presbyopic procedures, and because it has no refractive power there is no need to replace the inlay as patients age. Repositioning the inlay is possible, and if necessary it can be easily removed to allow other treatment options.
In the future, there is a potential for presbyopic correction with photo-phaco-modulation—radial femtosecond laser cuts intended to increase the elasticity of the crystalline lens and restore its ability to change shape as the eye focuses at different distances. Until then, the small-aperture corneal inlay will remain my preferred method for providing long-term maximum visual acuity with reduced spectacle dependence for my presbyopic patients.
Minoru Tomita, PhD, MD, is Executive Medical Director at the Shinagawa LASIK Center in Tokyo. Dr. Tomita states that he is a consultant to AcuFocus, Inc. He may be reached at e-mail: tomita@shinagawa-LASIK.com.
- Ambrósio R Jr, Tervo T, Wilson SE. LASIK-associated dry eye and neurotrophic epitheliopathy: pathophysiology and strategies for prevention and treatment. J Refract Surg. 2008;24:396-407.
- Salomão MQ, Ambrósio R Jr, Wilson SE. Dry eye associated with laser in situ keratomileusis: mechanical microkeratome versus femtosecond laser. J Cataract Refract Surg. 2009;35:1756-1760.
- Mian SI, Li AY, Dutta S, Musch DC, Shtein RM. Dry eyes and corneal sensation after laser in situ keratomileusis with femtosecond laser flap creation; effect of hinge position, hinge angle, and flap thickness. J Cataract Refract Surg. 2009;35:2092-2098.
- Tomita M, Kanamori T, Waring GO 4th, et al. Simultaneous corneal inlay implantation and laser in situ keratomileusis for presbyopia in patients with hyperopia, myopia, or emmetropia: six-month results. J Cataract Refract Surg. 2012;38:495-506.
- Tomita M, Kanamori T, Waring GO 4th, Nakamura T, Yukawa S. Small-aperture corneal inlay implantation to treat presbyopia after laser in situ keratomileusis. J Cataract Refract Surg. 2013;39:898-905.