If you have undergone PRK or LASIK Surgery and now require cataract surgery, very critical data must be obtained to determine the power of the intraocular lens that will be implanted in your eye. Mathematical formulae have been developed, IOL Nomograms, that require information about the curvature of the cornea in addition to other data about the pre-surgical eye. However, these Nomograms assume that the cornea has not been altered by refractive surgery. The BESSt Formula has been devised to account for the different relationship between the anterior and posterior curvatures of the post-excimer laser cornea. To assure that correct corneal curvature measurements are made, the Pentacam corneal measuring device is used.

For cataract patients who have not had prior excimer laser surgery, the IOL Nomogram that we use has achieved universal approval for its accuracy. Developed by Dr. Haigis of Germany,  the Nomogram uses the Pentacam's Anterior Chamber Depth Measurement (ACD). The ACD is the distance between the cornea and the anterior surface of the cataract. Requiring this information is intuitively desirable since this distance is approximately where the implanted IOL will be ultimately located. The final measurement introduced into the Haigis Nomogram is the axial length of the eye, measured extremely accurately by the Zeiss IOL Master.    

 

The Pentacam is used to analyze the curvature of the front and back of the corneal curvature and the distance between the cornea and the front surface of the lens, the Anterior Chamber Depth (ACD)