Byunghoon Chung1, Hun Lee2, Cynthia J Roberts3, David Sung Yong Kang4, Dan Z Reinstein5, Seung Ki Jean4, Eung Kweon Kim1, Kyoung Yul Seo1, Tae-Im Kim6. 1. Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea. 2. Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea; Department of Ophthalmology, International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, South Korea. 3. Department of Ophthalmology and Visual Science and Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA. 4. Eyereum Eye Clinic, Seoul, South Korea. 5. Department of Ophthalmology, Columbia University Medical Center, New York, New York, USA; London Vision Clinic, London, England; Centre Hospitalier National d'Ophtalmologie, Paris, France. 6. Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, South Korea. Electronic address: tikim@yuhs.ac.
Abstract
PURPOSE: To assess the agreement of decentration measurements between tangential curvature topography and tomography pachymetry difference maps after a small-incision lenticule extraction (SMILE) procedure. SETTING: Yonsei University College of Medicine and Eyereum Eye Clinic, Seoul, South Korea. DESIGN: Retrospective case series. METHODS: Decentrations and pupillary offset (angle κ) were analyzed and compared using two different methods. A difference map of the tangential curvature was generated with a Placido corneal topographer (Keratron Scout) and a pachymetry difference map was generated with a Scheimpflug tomographer (Pentacam) for each eye, using preoperative and 3-month postoperative scans. Decentrations were also compared using a vector difference plot for the two maps. RESULTS: The study comprised 155 eyes (155 patients). The magnitude of decentration was 0.27 mm ± 0.17 (SD) (range 0.02 to 0.88 mm) with the tangential curvature difference maps and 0.26 ± 0.20 mm (range 0.00 to 0.91 mm) with the pachymetry difference maps, showing no significant difference in the arithmetic values of decentration (P = .124). However, the vector difference in pupillary offset between preoperative and postoperative measurements from the pachymetry difference map significantly correlated with the magnitude of vector differences of decentration between the two maps (P = .007). The vector difference plot also showed a wide distribution spread to all 4 quadrants, demonstrating a lack of agreement. CONCLUSIONS: Although there was no significant difference between the scalar magnitude of decentration with the tangential topography difference maps and tomography pachymetry difference maps, the vector differences did not agree and increasing error was present with increasing differences in pupillary offset in the pachymetry difference maps.
PURPOSE: To assess the agreement of decentration measurements between tangential curvature topography and tomography pachymetry difference maps after a small-incision lenticule extraction (SMILE) procedure. SETTING: Yonsei University College of Medicine and Eyereum Eye Clinic, Seoul, South Korea. DESIGN: Retrospective case series. METHODS: Decentrations and pupillary offset (angle κ) were analyzed and compared using two different methods. A difference map of the tangential curvature was generated with a Placido corneal topographer (Keratron Scout) and a pachymetry difference map was generated with a Scheimpflug tomographer (Pentacam) for each eye, using preoperative and 3-month postoperative scans. Decentrations were also compared using a vector difference plot for the two maps. RESULTS: The study comprised 155 eyes (155 patients). The magnitude of decentration was 0.27 mm ± 0.17 (SD) (range 0.02 to 0.88 mm) with the tangential curvature difference maps and 0.26 ± 0.20 mm (range 0.00 to 0.91 mm) with the pachymetry difference maps, showing no significant difference in the arithmetic values of decentration (P = .124). However, the vector difference in pupillary offset between preoperative and postoperative measurements from the pachymetry difference map significantly correlated with the magnitude of vector differences of decentration between the two maps (P = .007). The vector difference plot also showed a wide distribution spread to all 4 quadrants, demonstrating a lack of agreement. CONCLUSIONS: Although there was no significant difference between the scalar magnitude of decentration with the tangential topography difference maps and tomography pachymetry difference maps, the vector differences did not agree and increasing error was present with increasing differences in pupillary offset in the pachymetry difference maps.