title: A comparison of two semi-quantitative surgical keratometers: the modified Hyde ruler and the Barrett keratoscope with "astigmatic dial".
abstract: The Hyde astigmatic ruler is an inexpensive, semiquantitative, hand-held, surgical keratometer that we modified by geometrically calculating the correct shape of its ellipses. The Barrett keratoscope is a cheap, disposable, qualitative keratometer that, unlike the Hyde ruler, produces a bright corneal image. We designed a transparent overlay, or "astigmatic dial," to use with the keratoscope. This overlay determines the magnitude of astigmatism and sets the distance the keratoscope is held from the cornea by direct comparison with the corneal image. Using a model cornea, we compared our modified Hyde ruler with the Barrett keratoscope and astigmatic dial to determine the accuracy of measurement provided by each. Both instruments had good predictive values for the true astigmatism; however, the Barrett keratoscope/astigmatic dial provided more consistent measurements of the astigmatism. We believe the keratoscope and dial provide a cheap, convenient, and accurate alternative to the more expensive microscope-mounted keratometers.
authors.affiliation: Department of Ophthalmology, University of New South Wales, Australia.
authors.forename: N
authors.initials: N
authors.lastname: Morlet
authors.forename: P
authors.initials: P
authors.lastname: Lindsay
authors.forename: P
authors.initials: P
authors.lastname: Cooke
mesh_terms: D001251:Astigmatism / Q000175:diagnosis* / Q000209:etiology / Q000517:prevention & control; D002138:Calibration; D002387:Cataract Extraction / Q000009:adverse effects / Q000295:instrumentation; D003315:Cornea / Q000473:pathology*; D006801:Humans; D008954:Models, Biological; D009885:Ophthalmology / Q000295:instrumentation*; D015203:Reproducibility of Results; D013536:Suture Techniques / Q000009:adverse effects