Novel diffractive intracorneal inlay improves presbyopia correction

Researchers have designed a new type of intracorneal inlay to correct presbyopia and other farsightedness.

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 other farsightedness. The inlay’s design is based on a diffractive lens with microholes that permit the flow of nutrients in the corneal stroma. This new type of prosthesis allows doctors to customize the treatment of presbyopia. 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 microholes necessary for the proper flow of nutrients, according to Juan A. Monsoriu, a researcher at the Polytechnic University of Valencia.

To reduce these undesired effects of light diffraction, the researchers redistributed the lens microholes in rings within a zone plate made for a specific area, permitting 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. It is possible to implant the device in both eyes without producing binocular vision problems, which is not feasible with inlays currently used. 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. The technique is also suitable for patients who have presbyopia with some refractive error. The inlay 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. Reference: W. D. Furlan et al., J. Biophotonics (2017); doi:10.1002/jbio.201600320.

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