Keratographer
The keratograph (also called video keratometer ) is an instrument for recording and evaluating the topography of the cornea . A Placido disk (ring system with concentrically alternating black and white rings) is projected onto the front surface of the cornea, the ring-shaped reflex images are recorded with a video camera and evaluated by a computer system with a Fourier analysis.
A major advantage compared to ophthalmic measurement is the number of measuring points. With an ophthalmometer measurement, only a few measuring points are recorded (two central, four peripheral). With the keratograph, depending on the device, 10,000 to 30,000 measuring points are recorded, the result is a detailed profile of the cornea. Different forms of representation can be selected. The corneal topography can be represented numerically, color-coded or as a three-dimensional area.
The keratograph was originally developed for corneal surgery . In the meantime, it is also widely used in contact lens fitting.
literature
- Harry Paul (Ed.): Lexicon of Optics Volume 1: A to L. Spectrum, Akademischer Verlag, Berlin et al. 1999, ISBN 3-8274-0382-0 .
- P. Keller, P. van Saarloos: Perspectives on corneal topography: a review of videokeratoscopy , Clinical and Experimental Optometry, 1997, Volume 80, Issue 1, pp. 18-30, doi : 10.1111 / j.1444-0938.1997.tb04843. x
- Josef F. Bille, Wolfgang C. Schlegel: Medical Physics 3: Medical Laser Physics . Springer, 2005, ISBN 978-3-540-26630-3 , pp. 16–18 ( limited preview in Google Book search).