Farhad Hafezi1, Sabine Kling2, Francesca Gilardoni3, Nikki Hafezi4, Mark Hillen4, Reyhaneh Abrishamchi3, Jose Alvaro P Gomes5, Cosimo Mazzotta6, J Bradley Randleman7, Emilio A Torres-Netto8. 1. Laboratory for Ocular Cell Biology, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland; Department of Ophthalmology, ELZA Institute, Dietikon, Switzerland; Department of Ophthalmology, USC Roski Eye Institute, University of Southern California, Los Angeles, California, USA; Faculty of Medicine, University of Geneva, Geneva, Switzerland; Department of Ophthalmology, University of Wenzhou, Wenzhou, China. Electronic address: farhad@hafezi.ch. 2. Department of Information Technology and Electrical Engineering, Swiss Federal Institute of Technology Zurich, Zürich, Switzerland. 3. Laboratory for Ocular Cell Biology, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland; Department of Ophthalmology, ELZA Institute, Dietikon, Switzerland. 4. Department of Ophthalmology, ELZA Institute, Dietikon, Switzerland. 5. Laboratory for Ocular Cell Biology, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland; Department of Ophthalmology, Paulista School of Medicine, Federal University of Sao Paulo, Sao Paulo, Brazil. 6. Department of Medicine, Surgery and Neurosciences, University of Siena, Siena, Italy; Department of Ophthalmology, Siena Crosslinking Center, Siena, Italy. 7. Department of Ophthalmology, The Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA. 8. Laboratory for Ocular Cell Biology, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland; Department of Ophthalmology, ELZA Institute, Dietikon, Switzerland; Department of Ophthalmology, Paulista School of Medicine, Federal University of Sao Paulo, Sao Paulo, Brazil; Faculty of Medicine, University of Geneva, Geneva, Switzerland.
Abstract
PURPOSE: To determine whether corneal cross-linking (CXL) with individualized fluence ("sub400 protocol") is able to stop keratoconus (KC) progression in ultrathin corneas with 12-month follow-up. DESIGN: Retrospective, interventional case series. METHODS: Thirty-nine eyes with progressive KC and corneal stromal thicknesses from 214 to 398 μm at the time of ultraviolet irradiation were enrolled. After epithelium removal, ultraviolet irradiation was performed at 3 mW/cm2 with irradiation times individually adapted to stromal thickness. Pre- and postoperative examinations included corrected distance visual acuity (CDVA), refraction, Scheimpflug, and anterior segment optical coherence tomography imaging up to 12 months after CXL. Outcome measures were arrest of KC progression at 12 months postoperatively and stromal demarcation line (DL) depth. RESULTS: Thirty-five eyes (90%) showed tomographical stability at 12 months after surgery. No eyes showed signs of endothelial decompensation. A significant correlation was found between DL depth and irradiation time (r = +0.448, P = .004) but not between DL depth and change in Kmax (r = -0.215, P = .189). On average, there was a significant change (P < .05) in thinnest stromal thickness (-14.5 ± 21.7 μm), Kmax (-2.06 ± 3.66 D) and densitometry (+2.00 ± 2.07 GSU). No significant changes were found in CDVA (P = .611), sphere (P = .077), or cylinder (P = .915). CONCLUSIONS: The "sub400" individualized fluence CXL protocol standardizes the treatment in ultrathin corneas and halted KC progression with a success rate of 90% at 12 months. The sub400 protocol allows for the treatment of corneas as thin as 214 μm of corneal stroma, markedly extending the treatment range. The DL depth did not predict treatment outcome. Hence, the depth is unlikely related to the extent of CXL-induced corneal stiffening but rather to the extent of CXL-induced microstructural changes and wound healing.
PURPOSE: To determine whether corneal cross-linking (CXL) with individualized fluence ("sub400 protocol") is able to stop keratoconus (KC) progression in ultrathin corneas with 12-month follow-up. DESIGN: Retrospective, interventional case series. METHODS: Thirty-nine eyes with progressive KC and corneal stromal thicknesses from 214 to 398 μm at the time of ultraviolet irradiation were enrolled. After epithelium removal, ultraviolet irradiation was performed at 3 mW/cm2 with irradiation times individually adapted to stromal thickness. Pre- and postoperative examinations included corrected distance visual acuity (CDVA), refraction, Scheimpflug, and anterior segment optical coherence tomography imaging up to 12 months after CXL. Outcome measures were arrest of KC progression at 12 months postoperatively and stromal demarcation line (DL) depth. RESULTS: Thirty-five eyes (90%) showed tomographical stability at 12 months after surgery. No eyes showed signs of endothelial decompensation. A significant correlation was found between DL depth and irradiation time (r = +0.448, P = .004) but not between DL depth and change in Kmax (r = -0.215, P = .189). On average, there was a significant change (P < .05) in thinnest stromal thickness (-14.5 ± 21.7 μm), Kmax (-2.06 ± 3.66 D) and densitometry (+2.00 ± 2.07 GSU). No significant changes were found in CDVA (P = .611), sphere (P = .077), or cylinder (P = .915). CONCLUSIONS: The "sub400" individualized fluence CXL protocol standardizes the treatment in ultrathin corneas and halted KC progression with a success rate of 90% at 12 months. The sub400 protocol allows for the treatment of corneas as thin as 214 μm of corneal stroma, markedly extending the treatment range. The DL depth did not predict treatment outcome. Hence, the depth is unlikely related to the extent of CXL-induced corneal stiffening but rather to the extent of CXL-induced microstructural changes and wound healing.
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