title: Correction on the distortion of Scheimpflug imaging for dynamic central corneal thickness.
abstract: The measurement of central corneal thickness (CCT) is important in ophthalmology. Most studies concerned the value at normal status, while rare ones focused on its dynamic changing. The commercial Corvis ST is the only commercial device currently available to visualize the two-dimensional image of dynamic corneal profiles during an air puff indentation. However, the directly observed CCT involves the Scheimpflug distortion, thus misleading the clinical diagnosis. This study aimed to correct the distortion for better measuring the dynamic CCTs. The optical path was first derived to consider the influence of factors on the use of Covis ST. A correction method was then proposed to estimate the CCT at any time during air puff indentation. Simulation results demonstrated the feasibility of the intuitive-feasible calibration for measuring the stationary CCT and indicated the necessity of correction when air puffed. Experiments on three contact lenses and four human corneas verified the prediction that the CCT would be underestimated when the improper calibration was conducted for air and overestimated when it was conducted on contact lenses made of polymethylmethacrylate. Using the proposed method, the CCT was finally observed to increase by 66 ± 34 μm at highest concavity in 48 normal human corneas.
authors.affiliation: Hong Kong Polytechnic University, Interdisciplinary Division of Biomedical Engineering, 11 Yuk Choi Road, Kowloon, Hong Kong SAR 999077, China.
authors.forename: Tianjie
authors.initials: T
authors.lastname: Li
authors.affiliation: Hong Kong Polytechnic University, Interdisciplinary Division of Biomedical Engineering, 11 Yuk Choi Road, Kowloon, Hong Kong SAR 999077, ChinabChinese PLA General Hospital, Department of Ophthalmology, Beijing 100039, ChinacCapital Medical University, Bei.
authors.forename: Lei
authors.initials: L
authors.lastname: Tian
authors.affiliation: Hong Kong Polytechnic University, Interdisciplinary Division of Biomedical Engineering, 11 Yuk Choi Road, Kowloon, Hong Kong SAR 999077, China.
authors.forename: Like
authors.initials: L
authors.lastname: Wang
authors.affiliation: Hong Kong Polytechnic University, School of Optometry, Hong Kong SAR 999077, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Hon
authors.affiliation: Hong Kong Polytechnic University, School of Optometry, Hong Kong SAR 999077, China.
authors.forename: Andrew K C
authors.initials: AK
authors.lastname: Lam
authors.affiliation: Chinese PLA General Hospital, Department of Ophthalmology, Beijing 100039, China.
authors.forename: Yifei
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Fudan University, Department of Electronic Engineering, Shanghai 200433, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Hong Kong Polytechnic University, Interdisciplinary Division of Biomedical Engineering, 11 Yuk Choi Road, Kowloon, Hong Kong SAR 999077, China.
authors.forename: Yongping
authors.initials: Y
authors.lastname: Zheng
mesh_terms: D000465:Algorithms; D016477:Artifacts; D003315:Cornea / Q000033:anatomy & histology* / Q000502:physiology*; D063171:Corneal Pachymetry / Q000379:methods*; D019781:Corneal Topography / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D010781:Photography / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity