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Intra-corneal Inlays

An intracorneal inlay is a very thin round disc that works on the principle of a pinhole camera.  It is implanted into the substance of the corneaThe cornea is the clear, transparent 'front window' of the eye through which light enters the eye. It handles about two-thirds of the focusing power of the eye and is critical for good vision. See Info on Eyes – Anatomy., under a flap that is similar to a LasikLasik is one of several types of laser treatments to permanently correct refractive errors of the eye. See Laser Vision – Introduction to Laser Treatment. flap, or into a pocket created by a femtosecond laserA femtosecond laser is the latest high-tech laser device used to make extremely accurate corneal incisions. See About Us – Our Technology – femtosecond laser..  By placing the disc inside the cornea, a smaller aperture is created where light may enter the eye, which gives patients an increased depth of field, which leads to a near focus with minimal impact on distance vision.  Unlike Lasik and PRKPRK is one of the laser treatment options to restore vision by permanently reshaping the cornea with an Excimer Laser. See Laser Vision – PRK., these inlays do not require the removal of corneal tissue but, similar to Lasik surgery, changes in vision are almost immediately apparent.

Patients with a spectacle script between +1.5 D and +2.5 D fare best with this inlay.  Since the procedure is reversible, it can be easily removed if the patient doesn’t like it or has difficulty adapting to it.

As at May 2013, 12 sites in the USA are investigating this technology.  The inlay is approved for use in Singapore and is about to receive the CE Mark in Europe.  A 24-patient study at the Singapore National Eye Centre found that after 3 months, patients could read words 1 mm high (better than they could with reading glasses).

Since the inlay is not a lensThe lens fulfils the same role as the lens in a camera. It handles about one-third of the focusing power of the eye and is critical for good vision.See Info on Eyes – Anatomy., it has no refractive power and patients will not have to replace it as they get older.  Moreover, it can be combined with cataractA cataract forms when the natural lens in the eye is, or is starting to become, opaque. If not treated, it can lead to blindness, which in most cases can be treated. See Cataract Centre – Understanding Cataracts. surgery, refractive surgery and monofocal lens implantation to provide better reading vision.

Kamravision

The KAMRA inlay, shown on the left, is manufactured by Focus in the USA and is currently the most widely used, with more than 15,000 implants globally.  It is only 3.8 mm in diameter, much smaller than a contact lens, lighter than a grain of salt and virtually invisible.  The inlay enables the patient to have better near visionNear vision is the ability to clearly focus on close-up opjects and fine print. See Other Options – Options for Refractive Correction. for reading menus, text messages and good intermediate vision for many real-life situations such as conversations and computer monitors.

This inlay went through several improvements – it is today being manufactured from highly biocompatible materials and the optimal depth in the cornea is well-defined.

Note the microscopic holes around the 1.6 mm central hole, which helps to maintain the physiological supply of nutrients in the whole cornea. 

Surgeons at the Shinagawa Lasik Centers have implanted nearly 10,000 Kamra corneal inlays since 2009.  Of those patients, 94% were happy with the results and 93% do not require spectacles for reading.

The inlay promises to be one of the best means to correct presbyopiaPresbyopia is an age-related condition. As we age, the natural lenses in our eyes gradually become inelastic and lose their ability to focus on nearby objects and fine print. From the age of 40 it becomes increasingly noticeable and people often jokingly complain that their 'arms are getting too short'. See Info on Eyes – Optics and Refractive Errors - Presbyopia. that is currently available.

How it works

The inlay is implanted in the non-dominant eye and employs the pinhole effect to increase the depth of field of an eye.  The small aperture in the center of the implant allows only focused light to reach the retinaThe retina is the receptor of light at the back of the eye. It fulfils the same function as the film in a film camera or the image sensor in a digital camera. The retina translates the images into electrical signals that are sent via the optic nerve to the visual cortex in the brain, where it is interpreted as the images we see. See Info on Eyes – Anatomy., improving near and intermediate vision with minimal impact on distance vision.

A femtosecond laser is used to create a flap or pocket at a depth of 200 microns (0.2 mm) in the cornea, into which the inlay is inserted.

Results so far have shown that the inlay can be implanted quickly and easily and that the procedure is reversible.  However, only 1.6% of patients asked for the inlays to be removed, usually because they had difficulty adapting to the new visual system.

According to the surgeons that routinely perform the implants, these inlays present fewer risks than other procedures for presbyopia, such as Lasik or refractive lens exchangeA refractive lens exchange is when the natural lens in the eye is replaced by one of several types of artificial lenses. See Other Options – Refractive Lens Exchange..  It is also not dependent on age-related refractive changes and is, therefore, theoretically a permanent procedure.