title: Comparison of the accuracy and reproducibility of the keratometer and the EyeSys Corneal Analysis System Model I.
abstract: The EyeSys Corneal Analysis System Model I measures corneal topography using digital image analysis of placido rings reflected off the cornea. With three observers, we compared the accuracy and reproducibility (precision) of the Marco Keratometer Model 1 and EyeSys Corneal Analysis System Model I using four poly(methyl methacrylate) spheres (37.50, 42.51, 47.54, and 55.06 diopters [D]), three steel spheres (40.50, 42.50, and 44.75 D), and 20 normal human eyes (41.50 to 46.00 D). For the spheres, the standard deviations of intra-observer and overall reproducibility for both devices were less than 0.12 D; the absolute mean differences between the measurements of the seven spheres and the known values were 0.25 D or more for two spheres as measured by the keratometer and none as measured by the EyeSys. For the normal corneas, the standard deviations of intra-observer and overall reproducibility for dioptric measurements were 0.07 D and 0.14 D for the keratometer and 0.13 D and 0.19 D for the EyeSys. The EyeSys Corneal Analysis System Model I exceeds keratometer accuracy in reading calibrated spheres and approaches keratometer reproducibility in measuring the 3-mm zone of normal human corneas.
authors.forename: D D
authors.initials: DD
authors.lastname: Koch
authors.forename: J S
authors.initials: JS
authors.lastname: Wakil
authors.forename: S W
authors.initials: SW
authors.lastname: Samuelson
authors.forename: E A
authors.initials: EA
authors.lastname: Haft
mesh_terms: D003315:Cornea / Q000033:anatomy & histology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008768:Methylmethacrylates; D015588:Observer Variation; D009885:Ophthalmology / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013232:Steel
chemical_list: D008768:Methylmethacrylates; D013232:Steel