CLINICAL SCIENCE Intrastromal Corneal Ring Segment Implantation by Femtosecond Laser for the Correction of Residual Astigmatism After Penetrating Keratoplasty Tatiana Moura Bastos Prazeres, MD,* Allan Cezar da Luz Souza, MD,* Nicolas Cesa ´rio Pereira, MD,* Fa ´bio Ursulino, MD,† Leon Grupenmacher, MD,* and Luciene Barbosa de Souza, MD* Purpose: To evaluate the safety and efficacy of intracorneal ring segments (ICRSs) aided by femtosecond (FS) laser for the correction of residual astigmatism after penetrating keratoplasty (PKP). Methods: This retrospective noncomparative study comprised 14 eyes of 14 patients with high astigmatism after PKP who had ICRS implantation by femtosecond laser. The study evaluated uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive astigmatism, and corneal maximum curvature. Results: The CDVA postoperatively improved after 3 months (P , 0.001) and 6 months (P , 0.001) compared with CDVA preoperatively. The CDVA at 3 months was similar to that at 6 months (P . 0.999) as well as the UDVA (P = 0.276). The preoperative astigmatism was higher than that after surgery (P = 0.001). The preoperative maximum curvature was higher than that of the post- operative maximum curvature (P , 0.001). Conclusions: The implantation of ICRSs using the femtosecond laser for residual astigmatism post-PKP was safe and showed satisfactory results. It reduced refractive astigmatism and maximum corneal curvature and improved UDVA and CDVA. Key Words: intracorneal ring segment, penetrating keratoplasty, femtosecond laser, keratoconus (Cornea 2011;30:1293–1297) R efractive errors, such as residual astigmatism after penetrating keratoplasty (PKP), are frequent and remain a challenge for surgeons of the anterior segment. The occurrence of a high degree of astigmatism in patients after PKP surgery has different causes. These include eccentric and irregular trephination of host cornea, intrinsic astigmatism or irregular-shaped cut of the donor tissue, donor diameter, suture tension, host peripheral thinning or ectasia, bad positioning of tissues, and the depth and type of suture. 1,2 Residual astigmatism may be corrected with glasses or rigid contact lenses for irregular astigmatisms. When optical methods fail to achieve satisfactory visual rehabilitation, surgical procedures may be necessary, such as selective removal of suture, relaxing incisions, transepithelial photo- refractive keratectomy (PRK), 3 astigmatic keratotomy, 4,5 wedge resection, 1,6–8 PRK, 9 and laser in situ keratomileusis (LASIK). 10,11 Besides the difficulty these techniques present, they do not always produce predictable results. 1,3–12 Implants of intracorneal segments are being used to correct corneal ectasia with a clear cornea, and the results are reported to be good. It is a safe procedure that does not affect the central visual axis of the cornea and has been used to treat keratoconus, pellucid marginal degeneration, post-LASIK ectasia, and post-PRK ectasia. 13–15 In this study, we evaluated the safety and efficacy of the intracorneal ring segment (ICRS) implantation for correcting residual astigmatism post-PKP using femtosecond (FS) laser. To our knowledge, this is the first study to evaluate ICRS implantation in a group of patients post-PKP using FS laser. MATERIALS AND METHODS This retrospective noncomparative study comprised 14 eyes of 14 patients with the diagnosis of keratoconus who were submitted to PKP and followed up in the postoperatory with a high degree of astigmatism after suture removal. All patients were informed appropriately about the procedure and signed informed consent statements. This study was approved by the department’s ethics committee. The patients had contact lens intolerance and had ICRS (Kerarings) implantation by FS laser (IntraLase, 60 kHz). The patients were submitted to slit-lamp examina- tion, manifest refraction, and corneal tomography with the Orbscan II (Bausch & Lomb). The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive astigmatism, maximum corneal curvature, and pachymetry were evaluated before surgery and 1, 3, and 6 months after surgery. Visual acuity was evaluated with a Snellen chart and converted to logarithm of the minimal angle of resolution (logMAR) values. Received for publication October 17, 2010; revision received February 17, 2011; accepted February 27, 2011. From the *Department of Ophthalmology, Sorocaba Eye Bank, Sorocaba, Sa ˜o Paulo, Brazil; and †School of Medicine, Federal University of Sergipe, Aracaju ´ , Sergipe, Brazil. The authors state that they have no proprietary interest in the products named in this article. Reprints: Tatiana M.B. Prazeres, Rua Conselheiro Correa de Menezes, n266, apt 701, Horto Florestal, Salvador, Bahia, CEP 40295-030, Brazil (e-mail: tatianaprazeres@hotmail.com). Copyright Ó 2011 by Lippincott Williams & Wilkins Cornea  Volume 30, Number 12, December 2011 www.corneajrnl.com | 1293