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Selecting and using a videokeratoscope for mapping of corneal topography (continuing education credit).

1. Modern videokeratography (VK) projects circular Placido rings onto the specular cornea where they are captured by a single or dual camera. The computer within the system employs electronic edge detection to analyze the reflected image(s), and a reconstruction algorithm transforms the two-dimensional circular pattern into a representation of the three-dimensional shape of the cornea. 2. The most familiar product of a videokeratoscope is a color-coded contour map of corneal surface power, in which cool colors represent low corneal powers and warm colors suggest high corneal powers. These maps provide both an accurate and highly intuitive method of determining the shape of the cornea. 3. The primary applications of VK are in determination of corneal curvature and astigmatism prior to and following refractive surgery, both photorefractive keratectomy (PRK) and radial keratotomy (RK), and in the diagnosis of keratoconus. Corneal mapping also is useful in the determination of other disease states. It is likely that within 5 years corneal topographical mapping will be mandatory measurement for all pre- and post-refractive surgery. 4. Consequently, every hospital and surgeon's office will soon have access to one or more videokeratoscopes. As systems become less expensive and more application-specific, the instruments will most likely become standard equipment for clinicians in the fitting of contact lenses. At that point, interaction with these systems will fall into the job description of virtually every nurse/technician. Many technicians will be called on to give quick selection criteria and advice to surgeons and physicians regarding videokeratography.