title: The disc damage likelihood scale (DDLS): interobserver agreement of a new grading system to assess glaucomatous optic disc damage.
abstract: BACKGROUND
  The disc damage likelihood scale (DDLS) is a new grading system to estimate the amount of optic disc damage in glaucoma patients. The objective of this study was to assess the interobserver agreement of the DDLS and the cup/disc ratio.
  
  
  METHODS
  The reproducibility of the DDLS and the cup/disc ratio was measured by two masked observers (one glaucoma specialist and one of two resident physicians in their first 6 months of training) staging 42 eyes of 25 patients with glaucoma or ocular hypertension. Disc size, cup/disc ratio and DDLS were documented and the Cohen's kappa was calculated as a measure for interobserver agreement.
  
  
  RESULTS
  The interobserver agreement for the cup/disc ratio was good (Cohen's kappa 0.803). For the DDLS, the interobserver agreement was even better (Cohen's kappa 0.902).
  
  
  CONCLUSIONS
  Unlike the cup/disc ratio, which focuses on the excavation, the DDLS is based directly on the thickness of the neuroretinal rim and takes into account the optic disc size. Therefore, the DDLS estimates the glaucomatous damage of the optic disc more precisely than the currently used method. Although this new grading system is more complicated to use in clinical practice, the interobserver agreement for the DDLS in our study setting was very good.
authors.affiliation: Department of Ophthalmology, Cantonal Hospital of Lucerne, Lucerne, Switzerland. frank.bochmann@ksl.ch
authors.forename: F
authors.initials: F
authors.lastname: Bochmann
authors.forename: J P
authors.initials: JP
authors.lastname: Howell
authors.forename: C
authors.initials: C
authors.lastname: Meier
authors.forename: C
authors.initials: C
authors.lastname: Becht
authors.forename: M A
authors.initials: MA
authors.lastname: Thiel
mesh_terms: D005260:Female; D005901:Glaucoma / Q000150:complications* / Q000473:pathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D015588:Observer Variation; D009901:Optic Nerve Diseases / Q000209:etiology* / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity