Corneal Inlay Under a LASIK flap — A Future Option for Treating Presbyopia (Reading Glasses)?

Blended vision or monovision LASIK is an excellent option for 80 percent of patients with presbyopia. This blog looks at future corneal inlay options for correcting presbyopia.

In my last blog entry, I talked about presbyopia — the age related loss of the ability to see up close. We looked at various LASIK strategies to address patients who are over age 40 and therefore are developing presbyopia. LASIK for stereo vision uses the laser to set both eyes for distance, which allows the best possible distance vision, the best possible depth perception, and the best possible night vision using LASIK — but leaves the patient requiring reading glasses at an age appropriate level. Full, or classical, monovision LASIK sets the dominant for distance vision and the non-dominant eye for close, reading vision. Monovision LASIK patients can see both near and far without glasses regardless of age. There is an inherent trade-off with monovision, however, in that the distance vision is not as good as with stereo vision LASIK. A third option we discussed was blended vision LASIK, also known as mini-monovison LASIK. With blended vision LASIK, the dominant eye is set for far and the non-dominant eye is set for the mid range. While this arrangement does not provide complete independence from reading glasses, it significantly decreases dependency on reading glasses for all but very small objects or print. The benefit is that it provides better quality distance vision than full monovision LASIK does.

In this blog, I want to take a look into the future and talk about non-laser corneal inlay technologies that are being developed to add to our set of options for patients with presbyopia. Interestingly, each of these technologies I’ll be discussing could still be performed in the future on someone who has LASIK today — and in fact they would require that patients first have excellent distance vision, whether by birth or by having LASIK. All three of these technologies work by placing a corneal inlay — a carefully machined bio-compatible material — under a LASIK flap to correct presbyopia in the non-dominant eye.

The first of these future corneal inlay technologies we’ll look at is the PresbyLens. The PresbyLens works by placing an inlay under a LASIK flap in the very center of the cornea. This will create a bulge in the overlying corneal surface of the flap. This central bulge helps focus some of the incoming light rays like a mini-magnifying glass. In this way, some light rays (those entering through the center of the cornea) allow the patient to see up close while other light rays (those entering through the surrounding, unbluged cornea) continue to allow the patient to see well in the distance.

The second inlay technology is called the Flexivue Microlens. This inlay also is placed under a LASIK flap. This inlay, however, works in an opposite strategy to that of the PresbyLens. Central light rays remain unaffected and still allow good distance vision while surrounding light rays enter through the magnifying portion of the donut like inlay.

The third inlay technology, the Kamra Corneal Inlay, works by yet a different strategy. Perhaps you have seen a pair of pinhole glasses at a State fair. Pinhole glasses create a focusing effect by selecting for already focused light rays and blocking others. The Kamra works by an analagous, but not identical, mechanism. It is best thought of as having a mini-pinhole placed under a LASIK flap to focus the near vision. The surrounding body of the inlay is fenestrated with thousands of micro-holes to allow nutrients to pass through the substance of the inlay.

All three of these corneal inlays are reversible. The PresbyLens and the Flexivue Microlens are cosmetically invisible to an observer, but some people feel the Kamra Corneal Inlay is, in fact, visible to an observer.

With all three of these inlays, the biggest remaining concern, however, is about the long term bio-compatability of the inlay material. Previous inlay technologies have caused problems by blocking nutrients, resulting in damage to the corneal tissue. Other older corneal inlays have shifted in position over time, causing optical problems. These current three technologies are very promising at this point, but more data is needed before they can be considered safe and ready for widespread use. It is also not clear whether these corneal inlay technologies will actually outperform blended vision LASIK or monovision LASIK for presbyopia. Currently, approximately 80% of patients are highly satisfied with blended vision or monovision as a solution to presbyopia.

Corneal Inlay Under a LASIK flap — A Future Option for Treating Presbyopia (Reading Glasses)?

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