Corneal Inlays

Corneal inlays improve near vision by several different mechanisms: changing corneal curvature, increasing depth of field via a small central aperture, or changing the refractive index of the cornea (see Fig 4-1B). The KAMRA corneal inlay (AcuFocus Inc, Irvine, CA) has been used successfully and is commercially availability in 49 countries. It was FDA approved in 2015 and is the first inlay to be available in the United States. It is 5 μm thick with a 3.8-mm outer diameter and a 1.6-mm central aperture. It “corrects” presbyopia via a pinhole effect, providing near vision in the nondominant eye in which it is implanted. Another inlay is the Flexivue Microlens (Presbia, Dublin, Ireland), a small, hydrophilic acrylic clear inlay with an index of refraction different from that of the cornea. A small hole in the center allows for distance vision and nutritional circulation. The Raindrop Near Vision Inlay (Revision Optics, Lake Forest, CA) is a hydrogel inlay 2 mm in diameter and 32 μm thick centrally. As a hydrogel, it allows nutrients and oxygen to pass through and, when placed centrally, causes central corneal steepening, resulting in variable power from center of the cornea to the periphery.

All currently available inlays are implanted only in the nondominant eye, which should have a stable refractive spherical equivalent of –1.00 to 0.00 D at the time of surgery. This value either can be the baseline refractive error or can be achieved with laser refractive surgery, such as LASIK, performed at least 1 month prior to implantation of the inlay. The inlay is typically placed in a corneal pocket created by a femtosecond laser, allowing for better centration, lower risk of corneal striae, and minimal impact on the peripheral corneal nerve innervation. The inlay must be centered on the visual axis, as even a slightly decentered placement can significantly affect the visual outcome.

Neuroadaptation to these inlays may take months. Because the procedure is performed only in the nondominant eye, some adverse visual effects (night halos) may be less perceptible in binocular viewing conditions. One of the benefits of corneal inlays is that they can be removed with few to no long-term sequelae. See Chapter 4 for more details.

• Bouzoukis DI, Kymionis GD, Limnopoulou AN, Kounis GA, Pallikaris IG. Femtosecond laser–assisted corneal pocket creation using a mask for inlay implantation. J Refract Surg. 2011;27(11):818–820.

• Garza EB, Gomez S, Chayet A, Dishler J. One-year safety and efficacy results of a hydrogel inlay to improve near vision in patients with emmetropic presbyopia. J Refract Surg. 2013; 29(3):166–172.

• Limnopoulou AN, Bouzoukis DI, Kymionis GD, et al. Visual outcomes and safety of a refractive corneal inlay for presbyopia using femtosecond laser. J Refract Surg. 2013;29(1):12–18.

• Lindstrom RL, Macrae SM, Pepose JS, Hoopes PC Sr. Corneal inlays for presbyopia correction. Curr Opin Ophthalmol. 2013;24(4):281–287.

• Tomita M, Kanamori T, Waring GO IV, et al. Simultaneous corneal inlay implantation and laser in situ keratomileusis for presbyopia in patients with hyperopia, myopia, or emmetropia: six-month results. J Cataract Refract Surg. 2012;38(3):495–506.

• US Food and Drug Administration. KAMRA Inlay - P120023. Approval April 17, 2015. Available at https://goo.gl/xzJHzY. Accessed November 6, 2016.

• Waring GO IV. Correction of presbyopia with a small aperture corneal inlay. J Refract Surg. 2011;27(11):842–845.

Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.