In keratophakia, a plus-powered lens is placed intrastromally to increase the curvature of the anterior cornea to correct hyperopia and presbyopia. After a central lamellar keratectomy is performed with a microkeratome or femtosecond laser, the flap is lifted, the lenticule is placed onto the host bed, and the flap is replaced and adheres without sutures. Lenticules can be prepared from either donor cornea or synthetic material; these types are referred to as homoplastic and alloplastic lenticules, respectively.
Homoplastic Corneal Inlays
A homoplastic inlay is created from a donor cornea by a lamellar keratectomy after removal of the epithelium and Bowman layer. The lenticule (fresh or frozen) is then shaped into a lens using an automated lathe. The lens can be preserved fresh in refrigerated tissue-culture medium, frozen at subzero temperatures, or freeze-dried.
Keratophakia has been used to correct aphakia and hyperopia of up to 20.00 D, but few studies on this procedure have been published. Troutman and colleagues reported on 32 eyes treated with homoplastic keratophakia, 29 of which also underwent cataract extraction. Even for procedures done by experienced surgeons, refractive predictability was still low: the eyes of 25% of patients were more than 3.00 D from the intended correction. Complications included irregular lamellar resection, wound dehiscence, and postoperative corneal edema. Although the procedure was originally intended to be used in conjunction with cataract extraction for the correction of aphakia, the complexity of the procedure and the unpredictable refractive results could not compete—in the early 1980s—with aphakic contact lenses or the improved technology of intraocular lens (IOL) implantation. Homoplastic keratophakia using tissue from stromal lenticule extraction has been suggested, however, for treating hyperopia, presbyopia, and ectatic corneal diseases.
Ganesh S, Brar S, Rao PA. Cryopreservation of extracted corneal lenticules after small incision lenticule extraction for potential use in human subjects. Cornea. 2014;33(12): 1355–1362.
Lim CH, Riau AK, Lwin NC, Chaurasia SS, Tan DT, Mehta JS. LASIK following small incision lenticule extraction (SMILE) lenticule re-implantation: a feasibility study of a novel method for treatment of presbyopia. PLoS One. 2013;8(12):e83046. www.ncbi.nlm.nih.gov/pmc/articles/PMC3859649/. Accessed November 6, 2016.
Sun L, Yao P, Li M, Shen Y, Zhao J, Zhou X. The safety and predictability of implanting autologous lenticule obtained by SMILE for hyperopia. J Refract Surg. 2015;31(6):374–379.
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.