Researchers at the Polytechnic University of Valencia, University of Valencia, the Medical Research Institute Hospital La Fe, and the companies AJL Ophthalmic SA and Aiken-Tecnología Ocular Preventiva SL (all in Valencia, Spain) have designed a new type of intracorneal inlay to correct presbyopia and farsightedness.
The inlay's design is based on a diffractive lens with micro-holes that permit the flow of nutrients in the corneal stroma. Also, this new type of prosthesis allows doctors to customize the treatment of presbyopia and farsightedness. Because of its high efficiency, the prosthesis can be implanted in both eyes without producing binocular vision. The design is easily adaptable to the shape of the intraocular lens and contact lens.
Current treatments for farsightedness include glasses, bifocal and progressive contact lenses, and multifocal intraocular lenses, as well as intracorneal inlays. However, "these prostheses are limited because of the reduction of the retinal image quality produced by the diffractive light passing through the micro-holes necessary for the proper flow of nutrients,” says Juan A. Monsoriu, a researcher at the Center for Physics Technologies at the Polytechnic University of Valencia.
To reduce those undesired effects of light diffraction, the researchers redistributed the lens micro-holes, which turns the diffraction produced by the holes into a beneficial factor. In addition, it is possible to implant it in both eyes without producing binocular vision problems, which is not feasible with inlays currently used.
"In our invention, the distribution of the micro-holes is concentrated in rings distributed inside a zone plate made for a specific area," says Waler D. Furlan, coordinator of the DiOG (Diffractive Optics Group) Research Group of the University of Valencia. "In addition, this new lens presents a new versatile design, as it permits a variable density of holes in each area, depending on the relative intensity wanted between the different focuses generated by the lens for correcting ocular aberrations."
For intracorneal inlays in emmetropic eyes, this is safer than laser-assisted in situ keratomileusis (LASIK) surgery, as the removal of the corneal tissue is not necessary. However, this technique is suitable for patients who have presbyopia with some refractive error.
The main advantages of this technique are that it allows patients with presbyopia to clearly see close objects and that can be customized depending on the visual needs of the patient (working distance, pupillary diameter, focus relative intensity, etc.). It offers the possibility of being used in both eyes without creating binocular vision problems, and it provides an extension of the depth of far focus of the eye and the near focus while guaranteeing an optimized range of clear vision for near and far objects.
Full details of the work appear in the Journal of Biophotonics.