Hydrogel Inlays May Replace Reading Glasses

Hydrogel corneal inlays could make reading glasses a thing of the past.Presbyopia is the technical name for the farsightedness that begins to afflict many people as they reach middle age. The change usually becomes apparent at about the age of 40, when books have to be held farther and farther away in order to focus on them. When performing close-up tasks, the individual may have trouble focusing and may get headaches related to eyestrain or fatigue. Even those who have corrective lenses for myopia (nearsightedness) may notice a change in their near vision.

It’s believed that over time the natural lens of the eye thickens and loses elasticity. The muscles around the eye cannot work efficiently due to the lack of flexibility of the lens, making it more difficult for the muscles to help the eye focus. Current treatments for presbyopia include prescription eyeglasses or bifocals, multifocal contact lenses, or LASIK surgery.

Hydrogel Inlay

Hydrogels have long been used to correct nearsightedness or myopia. However, a more recent discovery may also help those with age-related presbyopia.

A device called a corneal inlay is available now for treating this common issue. A hydrogel lens is surgically placed over the cornea of one eye. During the surgery a small, thin flap is created at the center of the cornea and the lens is placed inside. The flap is replaced over the lens, holding it in place. The whole procedure takes approximately 15 minutes and can be performed in a doctor’s office. The implantation of the hydrogel lens has proven more effective and has fewer complications than LASIK surgery since no tissue is removed. The biocompatible hydrogel is made up of 80% water, allowing for oxygen and nutrients to pass quickly and easily through to nourish the eye.

Types of Inlays

There are three types of corneal inlays on the market now, each offering different results:

  • A small-aperture inlay is a ring-shaped device with pinholes for light to pass through. The pinholes allow depth of focus, while the ring controls the amount of reflective light passing through, permitting better focus. The inlay of the type currently in use is 3.8mm in diameter and 5µm thick, with an aperture diameter of 1.6mm.
  • A corneal reshaping inlays lens improves vision at various distances. After implantation, the inlay modifies the curvature of the cornea, causing the front of the eye to work like a multifocal contact lens. The market version of this inlay uses a 2mm hydrogel lens similar to soft contact lenses.
  • The third corneal inlay, the refractive optic inlay, typically is implanted in the nondominant eye. The doughnut-shaped disk changes the refractive index of the cornea. The hole in the center of the lens allows nutrients to reach the cornea. The implant of this type currently in use measures 3mm and is 20µm thick and is made of the biocompatible hydrophilic polymers hydroxyethyl methacrylate and methyl methacrylate. The result of the implant is similar to wearing a multifocal lens. The device is permanent but can be replaced if a change in prescription is required.

Convenience Factor

Presbyopia is a bothersome condition. A corneal inlay could well mean you won’t ever waste time again searching for your reading glasses (you know, the ones that are on top of your head).

Image by ivonnewierink/123RF.
Source: “Replace Your Reading Glasses With Tiny “Raindrop” Implant,” by Andreea, www.sciencedump.com, September 2, 2014.
Source: “Corneal Inlays and Corneal Onlays,” by Vance Thompson, M.D., www.allaboutvision.com, March 2014.
Source: “Inlays and Presbyopia: The Next Frontier: A Look at Three Leading Approaches Using Inlays to Expand Presbyopic Patients’ Range of Vision,” by Christopher Kent, senior editor, www.reviewofophthalmology.com, February 10, 2014.
Source: “Intracorneal Inlays for Presbyopia,” by Roger F. Steinert, M.D., Disclosures, www.medscape.com, February 18, 2014.
Source: “Raindrop Near Vision Inlay,” by John Olkowski M.D. and Keith Holliday Ph.D., www.presbyopia-international.com.
Source: “Corneal Inlays for Presbyopia Correction,” by Richard L. Lindstrom, et al., Current Opinion in Opthalmology, July 2013, doi: 10.1097/ICU.0b013e328362293e.