title: Objective assessment of corneal staining using digital image analysis.
abstract: OBJECTIVE
  To validate a new objective digital image analysis technique to evaluate corneal staining.
  
  
  METHODS
  One hundred photographs of corneal staining from various ocular surface diseases in 100 patients were quantified by a new strategy: a combination of the difference of Gaussians (DoG) edge detection for morphologic properties of corneal erosions and the red-green-blue (RGB) systems and hue-saturation-value (HSV) color model for detection of color. To enhance the image, we adopted a median filter, Otsu thresholding, and contrast-limited adaptive histogram equalization (CLAHE). To validate the diagnostic value of this new strategy, the same photographs were also graded by two independent clinicians using the Oxford scheme and the National Eye Institute/Industry (NEI)-recommended guidelines. The correlation between the average subjective grade and objective image analysis measurement was evaluated using the Pearson's correlation coefficient.
  
  
  RESULTS
  The new algorithm showed a strong correlation with the clinical grading scale in the Oxford scheme and the NEI-recommended guidelines (R = 0.850 and 0.903, P < 0.001, respectively). The repeatability of the objective measurement was excellent (R = 0.994).
  
  
  CONCLUSIONS
  The new algorithm showed excellent correlation with the traditional subjective clinical grading scales. It may be useful for objective assessment of corneal staining, independent of disease conditions.
authors.affiliation: Department of Ophthalmology, Chung-Ang University College of Medicine, Chung-Ang University Hospital, Seoul, South Korea.
authors.forename: Yeoun Sook
authors.initials: YS
authors.lastname: Chun
authors.affiliation: Biomedical Engineering Branch, Division of Convergence Technology, National Cancer Center, Goyang, South Korea.
authors.forename: Woong Bae
authors.initials: WB
authors.lastname: Yoon
authors.affiliation: Biomedical Engineering Branch, Division of Convergence Technology, National Cancer Center, Goyang, South Korea.
authors.forename: Kwang Gi
authors.initials: KG
authors.lastname: Kim
authors.affiliation: Department of Ophthalmology, Kyung Hee University College of Medicine, Kyung Hee University Hospital, Seoul, South Korea.
authors.forename: In Ki
authors.initials: IK
authors.lastname: Park
mesh_terms: D000465:Algorithms; D004396:Coloring Agents; D003316:Corneal Diseases / Q000175:diagnosis*; D003941:Diagnostic Techniques, Ophthalmological; D019793:Fluorescein; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015203:Reproducibility of Results; D013194:Staining and Labeling
chemical_list: D004396:Coloring Agents; D019793:Fluorescein
keywords: clinical grading; corneal staining; correlation; objective measurement