title: A simple and effective video keratometric system.
abstract: We tested a personal computer-based video keratometric system used to analyze projected placido disk rings. The system consists of a Maloney surgical keratometer that projects the rings and a video camera attached to an operating microscope. Images of the rings were transmitted to a video image processing board and analyzed on a personal computer using an analysis program we developed. System precision was evaluated in 18 eyes. The values were compared with those obtained using a commercial photokeratometer (control). In all eyes, the principal meridian values differed from the controls by < 0.04 mm. In 15 eyes (83%), the measurements were within 0.03 mm of the controls. The corneal astigmatism values and cylindrical axes were within 0.12 diopters in 17 eyes (94%) and within 5 degrees in all cases, respectively. Our system, which can analyze placido disc rings projected from other systems, is sufficiently precise to measure the corneal radius of curvature and astigmatism.
authors.affiliation: Howe Laboratory of Ophthalmology, Massachusetts Eye & Ear Infirmary, Harvard Medical School, Boston, USA.
authors.forename: H
authors.initials: H
authors.lastname: Igarashi
authors.forename: M
authors.initials: M
authors.lastname: Kojima
authors.forename: S
authors.initials: S
authors.lastname: Igarashi
authors.forename: A
authors.initials: A
authors.lastname: Yoshida
authors.forename: H M
authors.initials: HM
authors.lastname: Cheng
mesh_terms: D002138:Calibration; D003315:Cornea / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D012044:Regression Analysis; D012984:Software; D013690:Television