Corneal Shape Evaluation by Using Laser Keratopography

Corneal topography assessment plays a fundamental role in the detection of keratoconus and the evaluation of the refractive surgery patient. The main drawbacks of the methods based on the use of Placido's disk (the most commonly used technique) have been pointed out recently, and new techniques are being sought that allow clinicians to be more confident about the measurement. Some years ago, we proposed a new technique based on a scan of the corneal surface with a low power HeNe laser beam; by measuring the deflection of the reflected beam, it is possible to compute the shape of the scanned cornea. In this paper, we explain the basic theory behind the method and present numerical simulations which show that errors in the surface heights of less than 1 µxm may be obtained. In this work, we do not consider the effect of experimental errors. We discuss some possible extensions and improvements to the theory.