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    Effect of corneal allogenic intrastromal ring segment (cairs) implantation surgery in patients with keratoconus according to prior corneal cross-linking status
    (2024) Yücekul, Burcu; Tanrıverdi, Cafer; Taneri, Suphi; Keskin Perk, Fatma Feyza Nur; Karaca, Yiğit; Kılıç, Aylin
    PURPOSE: To compare the effects of corneal allogenic intrastromal ring segment (CAIRS) implantation on topographical measurements and visual outcomes of patients with keratoconus with and without corneal cross-linking (CXL) prior to the time of implantation. METHODS: Sixty-seven eyes with corneal allograft intrastromal ring segment implantation (KeraNatural; Lions VisionGift) due to advanced keratoconus were included in the study. Thirty-seven eyes had no CXL and 30 eyes had had CXL before being referred to the authors. The changes in spherical equivalent (SE), uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), steep keratometry (K1), flat keratometry (K2), mean keratometry (Kmean), maximum keratometry (Kmax), and thinnest pachymetry were retrospectively analyzed 6 months after the implantation. RESULTS: The median age was 29 years in the CXL group and 24.0 years in the non-CXL group (P > .05), respectively. All topographical and visual parameters before implantation were similar in both groups (P > .05 for all parameters). At 6 months, CDVA, K1, and Kmean showed higher improvement in the non-CXL group than the CXL group (P = .030, .018, and .039, respectively). CONCLUSIONS: CAIRS surgery has a flattening effect on both the corneas with and without CXL. The cornea with prior CXL treatment had less flattening effect due to the stiffening effect of prior CXL.
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    Efficacy and safety of intracorneal allogenic ring segment implantation in keratoconus: 1-year results
    (Springer Nature, 2023) Aşık Nacaroğlu, Şenay; Yeşilkaya, Elif Ceren; Keskin Perk, Fatma Feyza Nur; Tanrıverdi, Cafer; Taneri, Suphi; Kılıç, Aylin
    BackgroundTo evaluate the safety and efficacy of corneal allogenic intrastromal ring segments in the management of keratoconus patients.MethodsThe retrospective, nonrandomized, interventional case series consisted of 65 keratoconic eyes of 49 consecutive patients who had ring segment-shaped corneal allografts (KeraNatural (R)) implanted in intrastromal tunnels created using a femtosecond laser. The main outcome measures were uncorrected visual acuity (UCVA), corrected distant visual acuity (CDVA), refraction, keratometry, and pachymetry. Computed tomography scans of the corneal surfaces were also performed preoperatively as well as 3, 6 and 12 months postoperatively.ResultsMean age was 29.5 +/- 7.3 years (median 29, range: 20-52 years). The mean UCVA improved from 0.91 +/- 0.50 logMAR preoperatively to 0.40 +/- 0.24 logMAR postoperatively at 6 month follow-up (p < 0.01) and the mean CDVA improved from 0.87 +/- 0.20 logMAR preoperatively to 0.27 +/- 0.06 logMAR postoperatively (p < 0.01). The mean spherical equivalent improved from -8.82 +/- 4.57 to -3.45 +/- 4.81D (p < 0.01). Average Keratometry decreased from 49.23 +/- 5.22 preoperatively to 45.63 +/- 4.89 D postoperatively (p < 0.01). Mean anterior and posterior maximum elevation were also decreased significantly (p < 0.01). In one patient, dislocation of the graft towards the tunnel incision site and dehiscense at the tunnel entrance were observed in the first week of the operation. Yellow-white deposits were observed in the segment tunnels in five cases after 6 months.ConclusionThis study demonstrated that implantation of corneal allograft ring segments is a viable alternative treatment for keratoconus with safety and good visual results.
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    Increasing depth of focus with allogeneic presbyopic inlays: 3-year results
    (NLM (Medline), 2023) Keskin Perk, Fatma Feyza Nur; Taneri, Suphi; Tanrıverdi, Cafer; Hacıağaoğlu, Sezer; Karaca, Zeki Yiğit; Kılıç, Aylin
    PURPOSE: To demonstrate the safety and efficacy of allogenic corneal inlays designed to increase the depth of focus (DoF) in treated eyes. SETTINGS: Medipol University Hospital, Istanbul, Turkey. DESIGN: Prospective case series. METHODS: This study includes 50 eyes of 25 patients with a follow-up of 3 years. Emmetropic patients with presbyopia had implantation of allogenic corneal inlays in the nondominant eye. The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and uncorrected near visual acuity (UNVA) were evaluated in all eyes. A subjective visual acuity test system (Multifocal Lens Analyzer 3.0 application) was used to analyze the DoF by measuring the defocus curves. RESULTS: No significant difference between the treated and fellow eyes in UDVA and CDVA was found, whereas UNVA was significantly better in the treated eyes ( P = .20, P = .07, P < .01, respectively). Comparing to the preoperative CDVA, there was a 1-line decrease in CDVA in 6 (%24) patients. The mean defocus curves reveal a DoF of 1.1 diopters (D) for the untreated eye at the logMAR = 0.2 threshold. By contrast, the mean DoF of the treated eye and binocularly was 2.8 D. The areas under the curve were significantly better in the near, intermediate, and total distances in the treated eyes, whereas it was better for the far distances in the untreated eyes. All values were significant ( P = .023 total, P < .01 others). CONCLUSIONS: Allogenic presbyopic inlay implantation may be safe and provided a clinically and statistically significant increase in the DoF leading to good far, intermediate, and near-visual acuity in emmetropic presbyopic patients.
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    Long-term results of sterile corneal allograft ring segments implantation in keratoconus treatment
    (2024) Keskin Perk, Fatma Feyza Nur; Tanrıverdi, Cafer; Karaca, Zeki Yiğit; Tran, Khoa D.; Kılıç, Aylin
    Purpose: To evaluate the efficacy and safety of sterile corneal allograft ring segments implantation for the treatment of keratoconus by analyzing long-term visual, refractive, and tomographic clinical outcomes. Methods: This prospective study included 62 eyes of 49 patients with keratoconus who underwent corneal allograft ring segments implantation at Istanbul Medipol University Faculty of Medicine between February 2020 and August 2022. Surgical outcomes using the Istanbul nomogram were evaluated in patients preoperatively and postoperatively at 1 month, 6 months, 1 year, and 3 years. Outcomes measured were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SE), spherical refraction (SR), cylindrical refraction (CR), topographic keratometric values, and corneal thickness at the thinnest point. Results: Preoperative mean UDVA and CDVA (LogMAR) were 0.96 ± 0.50 and 0.72 ± 0.47, respectively, and increased to 0.41 ± 0.34 and 0.22 ± 0.19 at the last visit (P < 0.001). There was a significant decrease in SE, SR, and keratometric values postoperatively (P < 0.001). There was no difference in CR and thinnest corneal thickness values (P = 0.333 and 0.154, respectively). The stromal and epithelial thicknesses measured by anterior segment optical coherence tomography were stabilized at 6 months and 1 year, respectively. No major complications or side effects were observed intraoperatively or postoperatively. Conclusions: This study demonstrated that sterile corneal allograft ring segments implantation is a safe and feasible treatment for keratoconus, yielding notable long-term visual outcomes with minimal implant-related complications.
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    Postoperative corneal remodeling after corneal allograft intrastromal ring segment (cairs) implantation for keratoconus: an oct study
    (2025) Yakut, Burcu; Tanrıverdi, Cafer; Keskin Perk, Fatma Feyza Nur; Aşık Nacaroğlu, Şenay; Altınbaş, Munise; Kılıç, Aylin
    Objectives: To demonstrate corneal remodeling after corneal allograft intrastromal ring segment (CAIRS) with an anterior-segment optical coherence tomography (AS-OCT). Design: A prospective observational single-center study. Methods: This observational study included keratoconus patients who underwent CAIRS implantation into a stromal tunnel. Topographical, refractive, and visual changes were obtained from the patient records. Epithelial thickness (ET), anterior stromal thickness (AST), allograft corneal ring thickness (ACRT), and posterior stromal thickness (PST) were measured on the first day and 1, 3, 6, and 12 months postoperatively using AS-OCT. Results: The study included 35 eyes of 27 patients with advanced keratoconus. The mean keratometry decreased from 48.26 ± 4.78 D to 44.50 ± 4.42 D at 1-year postoperatively (P = 0.004), mean corrected distance visual acuity increased from 0.29 ± 0.18 to 0.70 ± 0.24 (P < 0.001), and spherical equivalent (SE) decreased from -6.94 ± 4.32 D to -1.44 ± 4.44 D (P < 0.001). The mean AST decreased by 17.39 ± 5.78 μm in the postoperative 1 st month compared to 1 st day after surgery (P = 0.040). No statistically significant variations were observed in AST after the first month. There was no statistically significant difference in the mean ET, ACRT, and PST measurements between follow-up times. Significant negative correlations were found between SE change and ET (r = -0.543, P = 0.023) and between K1 change and ACRT (r = -0.548, P = 0.008). Conclusion: CAIRS is an effective treatment method to improve visual acuity and keratometry measurements and does not cause significant changes in graft thickness or recipient corneal epithelial and stromal thicknesses during the 1-year follow-up period. The observed correlations between SE, keratometry, and corneal thickness suggest that epithelial and stromal remodeling play crucial roles in postoperative outcomes of CAIRS.