“Painting” on Presbyopia Correction

Figure 1. Location of intracorneal channels filled with a biocompatible, opaque ink used in corneal tattooing.

One method of surgically correcting presbyopia is to insert a small aperture opaque inlay into the corneal stroma of the non-dominant eye; the pinhole optics it produces improve near vision by increasing the implanted eye’s depth of focus, and these days, the procedure involves creating a flap in the cornea by femtosecond laser, and placing the inlay underneath. But what if you could just “paint” a presbyopia-correcting ring on the cornea with the laser instead?

Abbott Medical Optics’ (AMO) Vladimir Lemberg, Jim Hill and Hong Fu believe they’ve found a way to do it… using femtosecond laser-assisted keratopigmentation – or corneal tattooing (1). Simply put, they used an AMO iFS femtosecond laser to create a 200 µm deep intracorneal ring, cut at a range of aperture sizes, in 12 freshly harvested porcine corneas. They then manipulated the corneal incision with a spatula to open the anterior side of it, and filled the channels with a biocompatible opaque ink (Figure 1). They conducted theoretical analyses of the blur and image quality as a function of defocus and pupil size.

What they found was that in all cases, the laser produced complete, precisely centered ring cuts on the corneas; that the injected dye spread to cover the annulus of the ring cut and formed an aperture; and that the dye spreading resulted in a tendril-type pattern at the inner and outer edges of the cuts (Figure 2). The theoretical analyses showed that up to 3 diopters’ depth of focus can be achieved with reasonable aperture sizes.

Figure 2. Pig corneas with the presbyopia-correcting corneal tattoo.

Could the results of this study signal the introduction of a new, unique approach to presbyopia correction? Not just yet. While the authors believe that this technique should have “several advantages over a ring-like inlay, such as the absence of foreign body sensation, elimination of displacement danger, and improved nutrient flow” they confirm that “further research is required to confirm the findings from this preliminary study.”