Pentacam

Overview: A prerequisite to performing safe and precise laser refractive surgery is the ability to accurately measure the shape, thickness and contour of the cornea both pre and postoperatively. Will Vision & Laser Centers continues to lead the way by introducing state-of-the-art micro-imaging technology to the Pacific Northwest in the form of the Pentacam.   As the regional leader in laser vision correction, Will Vision is the one of the few centers in SW Washington and Oregon that provide patients with the advantages of the advanced Pentacam system.

Orbscan No Longer the Standard: In recent past, the primary technology used to provide refractive surgeons with detail on the shape of the cornea was the Orbscan II from Bausch and Lomb. Although this device has historically been the method used by most surgeons, the scanning slit technology upon which it is based is unable to provide sufficient accuracy to precisely image the anterior surface of the cornea and it demonstrates particularly poor accuracy when attempting to image the posterior surface of the cornea, especially in cases of thin cornea or those that are postop refractive surgery.   In many cases, these are the very corneas where it is imperative to obtain accurate information. As a consequence, the Orbscan II technology is no longer the gold standard for refractive surgery.

Why Pentacam is Superior: The Pentacam images the anterior segment of the eye by a rotating Scheimpflug camera measurement. This rotating process supplies pictures in three dimensions. The center of the cornea, which is most critical for refractive surgery planning, is measured very precisely because of this rotational imaging process. The measurement process lasts less than two seconds and minute eye movements are captured and corrected simultaneously. As a result of the short imaging time and 3-D image stitching it is possible to measure 25,000 true elevation points precisely and reproducibly.

Complete 3-D Analysis of Cornea and Lens: The Scheimpflug camera also provides a complete 3-D image of the entire anterior portion of the eye. This is not possible with the Orbscan II.

Corneal Topographic Analysis: Topography involves making a map that describes the elevations and depressions on the surfaces of the cornea similar to the way that a topographic map illustrates the mountains and valleys on a geographic terrain. With the Pentacam, topographic analysis of the corneal front and back surfaces is based on the true elevation measurement from one side of the cornea to the other (limbus to limbus). In addition to the larger area, the Pentacam provides significantly more accurate elevation measurements than the Orbscan II. In addition, other Placido disc based topographic devices must infer elevation from curvature data. Such inferences can lead to improper medical conclusions.

Corneal Thickness or Pachymetry:One of the most important measurements about the cornea besides its shape is the true thickness. Because the Pentacam provides highly accurate information about both the front and back surfaces of the cornea, it is possible to generate 25,000 data points that describe the true thickness of the cornea across its entire breadth and width. This is the ideal as even manual ultrasound pachymetry can only image one single data point making it nearly impossible to provide the amount of thickness detail that can be obtained with the Pentacam. Also, due to the inaccuracy of the Orbscan’s data on the posterior corneal surface, it is well recognized amongst eye surgeons that the pachymetric data that it provides is frequently incorrect.

Cataract Analysis: Clouding or opacification of the natural lens can be quantitatively imaged and analyzed using the Pentacam. The high quality of the Scheimpflug image allows pre-operative screening to help identify patients that would be better suited to intraocular lens implantation than laser vision correction. This provides the surgeon with a superior tool for preoperative assessment of a patient’s candidacy for vision corrective surgery.

Comparison Screens: To obtain the optimal impression of any general changes of the cornea or after refractive surgery, the Pentacam provides the surgeon with accurate comparison and difference maps.
 The specific effect of contact lens wear or surgical effect can be accurately quantified. Comparison of pre-op and post-op topographies is easy. Both front and back corneal surfaces can be selected for analysis in axial, tangential or elevation representation modes providing form maximum accuracy and flexibility.   The rapid imaging and eye tracking

Tomography: The Tomography calculates a virtual model of the anterior segment of the eye. It is possible to move, zoom and rotate it to detect e.g. iris defects, cornea incisions e.g. RK (Radial Keratotomy) or size, location and shape of cloudy areas or ‘opacifications’ in the crystalline lens. The slicing function in the three dimensions offers a detailed view of the different layers of the eye. The Tomopgraphy is a particularly helpful tool to explain to the patient the individual conditions of his eye.

Improved IOL Calculations:  Patients that have previously undergone corneal surgery and subsequently develop cataracts have frequently posed a significant problem, as the calculations for the power of the lens to implant have frequently been inaccurate. This problem is well known and several methods have been tried to get proper k-readings for the calculation of the IOL but no method has been precise enough.   In fact, all the methods which have been in use so far are based entirely upon assumptions and approximations. The Pentacam system provides the surgeon with an accurate program, developed in conjunction with Dr. Jack T. Holladay, to improve the calculation of IOLs for patients which have undergone corneal surgery. The Pentacam is the first and only machine that delivers the required values.