Pentacam – The CSO Sirius Topographer and Scheimpflug Camera is a combined device consisting of placido’s disc and a slit illumination system with a Scheimpflug camera which rotates around the eye to give an automatic measurement of an over-all view of the anterior segment of the eye. It provides topographic data on elevation and curvature of the entire anterior and posterior corneal surface,as well as the thickness of the cornea and depth of anterior chamber of the eye ,its used before refractive surgeries and cases of kerataconus detection and monitoring, and glaucoma screening.
HOW DOES IT WORK?
Pentacam works by illuminating a thin layer within the eye through its slit illumination system. The cells in the eye are not entirely transparent and scatter in the slit light, in doing so they create a sectional image which is then photographed in side view by a camera. The Scheimpflug camera captures an image of the illuminated plane from the anterior surface of the cornea right up to the posterior surface of the crystalline lens. While swiveling around the eye, the slit-camera device generates a series of radially oriented images of the anterior eye chamber. In the subsequent analysis of the sectional images, tissue boundaries are detected and point clouds are assigned to the various tissue layers (anterior and posterior corneal surfaces, iris and crystalline lens).
The sectional images are saved, corrected in relation to a common reference point and then put together to create a three-dimensional model of the entire anterior eye chamber. This makes it possible to generate reproducible tomographic images of the anterior eye chamber in any desired plane.
After correction for Scheimpflug distortion and light refraction, a tissue interfaces the exact location of image edge points in the eye by means of raytracing. Eye movements during image acquisition are captured by a second camera (pupil camera) and are also taken into account in the mathematical evaluation. This produces a set of three-dimensional measurement data which gives a precise geometric description of the anterior eye segment. This data in turn can be used to generate data on elevation, curvature, pachymetry, depth of the anterior eye chamber etc., in the well-known form of colour maps.