Placido topography is based on analyzing reflections of concentric Placido rings on the eye’s tear film, and therefore depends on a stable tear film for accurate results. Due to the need for a central camera, Placido systems cannot project rings onto the central cornea—meaning the most clinically important area is extrapolated rather than directly measured. Additionally, Placido topography provides data only on the anterior corneal surface.
In contrast, Scheimpflug imaging, as used in the Pentacam®, captures true cross-sectional images of the anterior eye segment, providing accurate, tear film–independent measurements. This technology delivers direct measurements of the central cornea and calculates data from both the anterior and posterior corneal surfaces. The integration of Placido technology is unnecessary for enhancing Pentacam® results—an assertion supported by extensive clinical research.
