Placido topography is a technology based on the reflection of Placido discs on the tear film of the eye. By definition it therefore requires a stable tear film. Furthermore Placido topography requires a central camera which automatically eliminates central Placido discs to be projected on the cornea, resulting in the central (most important area for measurement) to be extrapolated and not actually measured. Placido topography can only give information about the anterior cornea.
Scheimpflug technology is essentially: Scheimpflug photography – accurately taking images of the anterior section of the eye. This is not being influenced by the tear film, central data is measured and not extrapolated, and data from anterior and posterior cornea calculated. The inclusion of Placido technology is not needed to enhance the Pentacam® measurement. Clinical studies have proven this concept.