The researchers found, on average, the participants gained 2.9 lines on a reading chart, and the results remained steady over the follow-up.
Currently, there are three designs of corneal inlays, each varying in size, material and mechanism of action. While some of them are in clinical trials in the US, none has yet been approved for commercial use by the Food and Drug Administration (FDA).
Generally, corneal inlays have complications such as haziness that can be treated with steroids, but newer designs are managing to minimize these. If necessary, corneal inlays can be removed, making the treatment reversible, unlike other procedures such as LASIK laser eye surgery for presbyopia.
John Vukich, a clinical adjunct professor in ophthalmology and vision sciences at the University of Wisconsin, Madison, presented the results of a study on the efficacy of the KAMRA corneal inlay at AAO 2014, the 118th annual meeting of the American Academy of Ophthalmology, that is running from October 17th to 21st in Chicago, IL.
Prof. Vukich says corneal inlays are "a great opportunity to improve vision with a safety net of removability," and the study results show the KAMRA inlay is "a solution that truly delivers near vision that transitions smoothly to far distance vision."
The KAMRA inlay is a thin, flexible ring with a diameter of 3.8 mm and a hole measuring 1.6 mm in the middle. Once implanted in the cornea - the clear tissue covering the front of the eye - it acts like a camera aperture, adjusting the depth of field to enable near and far vision.
It takes about 10 minutes to implant the inlay, and the patient only needs a local anesthetic to numb the surface of the eye.
Prof. Vukich and colleagues carried out a prospective non-randomized study of the KAMRA inlay in 507 non-nearsighted patients with presbyopia aged between 45 and 60 who attended clinics in different parts of the US, Europe and Asia. After implanting the devices, they followed the patients for 3 years.
Corneal inlays gave 83% of presbyopic patients 20/40 vision
They found that in 83% of the presbyopic patients, the corneal implant allowed them to see with 20/40 vision or better over the follow-up period. This is considered the standard for being able to read newsprint or drive a vehicle without requiring glasses.
The researchers found that, on average, the participants gained 2.9 lines on a reading chart, and the results remained steady over the follow-up.
The KAMRA inlay is already available for commercial use in Asia, Europe and South America. In the US, it is classed as an investigational device, not yet approved by the FDA so not available for sale.
Two other types of corneal inlays - the Raindrop Near Vision Inlay that works by changing the shape of the cornea and the Presbia Flexivue Microlens that changes the refractive index of the cornea - are also in development for the US market.
In July 2014, Medical News Today learned how a team of scientists grew human corneal tissue in mice from stem cells. They hope the breakthrough will one day help people whose eyesight is lost or damaged due to burns and other injuries to the cornea.