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Detection of postlaser vision correction ectasia with a new combined biomechanical index
Riccardo Vinciguerra1, Renato Ambrósio, Ahmed Elsheikh
1From the Humanitas San Pio X Hospital, Milan, Italy (Vinciguerra, Rosetta); The School of Engineering, University of Liverpool, Liverpool, United Kingdom (Vinciguerra, Elsheikh, Eliasy, Lopes); Department of Ophthalmology, the Federal University of the State of Rio de Janeiro (UNIRIO), Rio de Janeiro, Brazil (Ambrósio); Department of Ophthalmology, the Federal University of São Paulo (UNIFESP), São Paulo, Brazil (Ambrósio, Torres-Netto); Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China (Elsheikh); NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, United Kingdom (Elsheikh); ELZA Institute, Dietikon/Zurich, Switzerland (Hafezi, Torres-Netto); Faculty of Medicine, University of Geneva, Geneva, Switzerland (Hafezi); USC Roski Eye Institute, Miller School of Medicine, Los Angeles, CA (Hafezi); School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, China (Hafezi, Lu); Eyereum Eye Clinic, Seoul, Korea (Yong Kang); Augenklinik am Neumarkt, Cologne, Germany (Kermani); Department of Ophthalmology, Osaka University Graduate School of Medicine, Osaka, Japan (Koh); School of Medicine and Health Sciences, University of Antwerp, Wilrijk, Belgium (Lu); Emmetropia Mediterranean Eye Institute, Heraklion, Greece (Lu); Department of Cornea & Refractive Surgery, Medical Research Foundation, Chennai, India (Padmanabhan); Department of Ophthalmology & Visual Science, Department of Biomedical Engineering, The Ohio State University, Columbus, OH (Roberts); Center for Refractive Surgery Muenster, Muenster, Germany (Taneri, Rost); University Eye-Clinic, Ruhr-University, Bochum, Germany (Taneri); Eye Care, Miami, FL (Trattler); Humanitas University, Department of Biomedical Sciences, Milan, Italy (Vinciguerra); Humanitas Clinical and Research Center-IRCCS, Rozzano (Mi) Italy (Vinciguerra); The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea (Jum); Medical Research Foundation, Chennai, India (Padmanaban); University of Zurich, CABMM, Ocular Cell Biology Group, Zurich, Switzerland (Torres-Netto).
Purpose:
To validate and evaluate the use of a new biomechanical index known as the Corvis biomechanical index-laser vision correction (CBI-LVC) as a method for separating stable post-LVC eyes from post-LVC eyes with ectasia.
Setting:
10 clinics from 9 countries.
Design:
Retrospective, multicenter, clinical study.
Methods:
The study was designed with 2 purposes: to develop the CBI-LVC, which combines dynamic corneal response (DCR) parameters provided by a high-speed dynamic Scheimpflug camera (CorVis ST; OCULUS Optikgeräte GmbH) and then to evaluate its ability to detect post-LVC ectasia. The CBI-LVC includes integrated inverse radius, applanation 1 (A1) velocity, A1 deflection amplitude, highest concavity and arclength, deformation amplitude ratio of 2 mm, and A1 arclength in millimeters. Logistic regression with Wald forward stepwise approach was used to identify the optimal combination of DCRs to create the CBI-LVC and then separate stable from LVC-induced ectasia. Eighty percentage of the database was used for training the software and 20% for validation.
Results:
736 eyes of 736 patients were included (685 stable LVC and 51 post-LVC ectasia). The receiver operating characteristic curve analysis showed an area under the curve of 0.991 when applying CBI-LVC in the validation dataset and 0.998 in the training dataset. A cutoff of 0.2 was able to separate stable LVC from ectasia with a sensitivity of 93.3% and a specificity of 97.8%.
Conclusions:
The CBI-LVC was highly sensitive and specific in distinguishing stable from ectatic post-LVC eyes. Using CBI-LVC in routine practice, along with topography and tomography, can aid the early diagnosis of post-LVC ectasia and allow intervention prior to visually compromising progression.
