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Peer Review | Sept '13

Presbyopia Correction: The Corneal Approach

What is the Holy Grail? In ophthalmology, the ideal surgical treatment option to correct presbyopia may be just that. Ideally, the restoration of true accommodation would reverse this universally inevitable process, but this has proven to be very challenging. In the meantime, there are several promising corneal therapies that are on the horizon. Take a look below to learn about the various corneal inlays and a femtosecond laser procedure for presbyopic correction.

To start with, let’s remember that monovision is still a fantastic procedure that has an extremely high success and satisfaction rate. Hayashi and others demonstrated in a fairly recent publication that in pseudophakic monovision, 1.00 D of anisometropia does not affect stereoacuity. A 1.50-D difference provides very adequate distance-corrected binocular near vision of ~20/38, with a slight compromise to steroacuity.1 Take this information into consideration, as some of the corneal procedures discussed below are modified forms of monovision, providing greater near vision with less impact on uncorrected distance visual acuity.

Regarding corneal inlays, there are several that have been used abroad for quite a few years and some that are in FDA clinical trials. The overall results are very promising, and each inlay is different by design. The Kamra (AcuFocus, Inc.) is a small-aperture corneal inlay that serves as a functional corneal pinhole. It is ~ 5 µm thick and does not alter the corneal curvature. The Kamra can be placed within a LASIK flap or a corneal pocket. A study showed its impressive success results in a group of post-LASIK patients, placed in a pocket, deep to the prior corneal flap, in the nondominant eye. Six-month results show an average of 4 lines of improvement in near vision from J8 to J2.2

Watch a discussion of inlays

The Flexivue Microlens (Presbia) is a 3-mm bifocal implant made of a hydrophilic polymer. The central zone has no refractive power, while near add is in the periphery, functionally creating a variation to the multifocal cornea. Limnopoulou et al demonstrated results that this implant may serve in a functional monovision modality, improving uncorrected near vision to at least 20/32 in 75% of the 47 eyes, while compromising the uncorrected distance vision to ~20/50.3

See the surgery

Lastly, the Raindrop Near Vision Inlay (ReVision Optics, Inc.) is a 2-mm hydrogel implant, similar in feel to a contact lens that steepens the anterior curvature of the central cornea. Although shown in a smaller study of 19 eyes, these eyes also appear to gain a significant improvement in their near vision of at least 20/40, while maintaining decent distance acuity of ~20/25.4

See the procedure

The applications of the femtosecond laser are ever expanding, and there are a number of studies abroad demonstrating its utilization in presbyopia correction with a procedure known as Intracor (Technolas Perfect Vision GmbH). This intrastromal femtosecond laser surgery creates five concentric rings and shrinks the surrounding collagen to create a multifocal cornea. The corneal net power appears to increase by ~0.70 D to 1.10 D, and the near vision improves from ~20/100 to an average of 20/30, as demonstrated by Manessa et al.5

Check out the procedure

The surgical correction of presbyopia is an ever-evolving science. Of note, none of the procedures mentioned in this article are yet FDA approved, but these options appear safe and effective, and at least a few of them will likely be part of our practices in the not-too-distant future.

Abstract 1, Abstract 2, Abstract 3, Abstract 4, Abstract 5

Elizabeth Yeu, MD

Elizabeth Yeu, MD, is an Assistant Professor of Ophthalmology at Eastern Virginia Medical Schooland a Partner specializing in cornea, cataract, and refractive surgery at Virginia Eye Consultants in Norfolk, Virginia. She may be reached at eyeu@vec2020.com.