Corneal topography, often referred to as photokeratoscopy or videokeratography, is a technology frequently relied upon by optometrists in the eye care health field. It uses computerized equipment and analytic software to measure the natural curvature of the human cornea. Using a unique system of concentric rings projected onto a person’s cornea, a virtual image is created from which calculations are made to determine cornea curvature. These measurements are then mapped out in the form of a color-coded, multi-dimensional printout that resembles a topography map one might encounter in a geography textbook.
In the past, keratometers measured just four points across a small central portion of the cornea. Today’s corneal topography equipment can evaluate as many as 10,000 specific points across the entire surface of the cornea. This allows for a much more precise and accurate measurement.
Corneal topography is instrumental in diagnosing and monitoring the progression of two particular eye conditions: keratoconus and pellucid marginal degeneration. Both of these conditions can impair vision once the cornea begins to steepen or change shape. It is also invaluable when it comes to evaluating Laser-Assisted in Situ Keratomileusis (LASIK) or radial keratotomy patients both before and after surgery. In addition, it can also be used in pre- and post-surgical penetrating keratoplasty cases.
Prior to surgery, optometrists can use corneal mapping to identify any potential problems that may exist, including scarring and irregular stigmatism. After surgery, corneal topography can monitor the success of the surgery and determine if the eye is healing properly. When it comes to contact lenses, cornea topography is useful during both the design and fitting stages. Photokeratoscopy software is such that lens details, including material, size, and design, can be determined on a case-by-case basis.
Although the price tag for the equipment can be very high, there is little doubt that this technology has become a standard in eye care. To encourage equipment purchase, many manufacturers offer leasing packages to offset initial investment costs. In addition, many are of the opinion that the technology has led to shorter office visits for patients as well as increased and invaluable patient satisfaction.
From the patient’s perspective, having a corneal topography procedure is quick and painless. The patient simply presses his or her face up against the machine’s round, lit bowl while a technician takes a series of pictures. The computer will quickly generate an image using different colors to indicate different grades of steepness, just like a topographical map of a landscape uses different colors to show changes in altitude.