"Presbyopia" is a naturally-occurring condition that usually appears as people enter their forties and makes reading materials blurry without the use of reading glasses or multifocal lenses. In presbyopia, the crystalline lens inside the eye becomes thicker and more difficult to change shape to keep small print, computers or hobby materials clear. This is not a disease or an abnormality, but is a normal change associated with aging. There is no “cure” for presbyopia, but modern technology can make it easier to live with.
Some people who enter presbyopia never having had the need for either eyeglasses or contact lenses to correct their distance or near vision find this new need for single-vision reading glasses or multifocal lenses irritating and annoying.
The KAMRA Inlay, a device that is implanted into the cornea to provide clear reading vision, is meant specifically for those patients who have no significant refractive error for distance but who are now presbyopic and need either reading glasses or multifocals.
Specifically, candidates for the procedure should be between ages 45 to 60, have a low refractive error between +0.50 and -0.75 sphere, less than 0.75 D of astigmatism, and who do need a reading lens power of +1.00 to +2.50, according to information available on the manufacturer’s web site.
The manufacturer, AcuFocus, has been developing and perfecting the KAMRA, which is implanted into the cornea using a laser to form a pocket that holds it in place. As shown in the illustration on the left, the inlay has a ring shape and is much smaller than a typical contact lens, shown on the right. The size (about 4 millimeters in diameter) and fenestrations in the design allow nutrients to flow almost unimpeded into the cornea and reduce post-surgical complications. Placed in the non-dominant eye, it apparently does not interfere in any significant way from normal vision. The implantation is much less invasive than other types of refractive surgery.
The inlay has been available previously in Canada, Europe, Asia and Latin America, providing extensive postmarket data for the FDA approval process. More than 20,000 inlays have been implanted; more than 80% of participants gained near visual acuity of at least 20/40 twelve months post-procedure, which is the level of vision needed to read most magazines and newspapers.
The KAMRA device has no refractive power, but works in a similar way as a camera with a small aperture; this gives the individual eye a much greater depth of focus and allows clear vision at all distances.
Because of the changes to the optics of the cornea and ocular tissues, patients will need to allow for some adaptation time. Most patients experience improved vision from one to four weeks after the inlay is placed.
Some patients, unfortunately, are not be good candidates for the inlay, including those who have had cataract surgery or have severe dry eye symptoms, ongoing eye infections or inflammations, corneal degenerations that are associated with decreased thickness or irregular shape of the ocular surface. Those with recent or recurring herpes eye infections or ongoing complications resulting from one, uncontrolled glaucoma, diabetes or active autoimmune or connective tissue disease should not undergo the procedure. Product labeling warns that the KAMRA Inlay’s safety and effectiveness is not known in those who have had LASIK or other refractive procedures.
As with any surgical intervention, there is the chance of adverse events or complications, including glare, halos, night vision problems or blurred vision. While the device can be easily removed if necessary, this does not always allow a complete return to prior vision. Possible corneal complications include swelling, clouding, thinning and potential corneal perforation; in addition, it can make evaluating and treating other eye problems more difficult.
It does appear that the KAMRA Inlay will allow eye surgeons and their patients another option in the treatment of presbyopia, thanks to new manufacturing technology and biocompatible materials.
