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Abstract
Pentacam is a multipurpose instrument that is capable of external ocular photography, corneal pachymetry, corneal topography, densitometry and anterior chamber analysis.
The Pentacam imaging device has been operational in ophthalmic practice since it was approved for use in the United States in 2004. The Pentacam is considered as a multifunctional imaging device by the manufacturer. The reliability of Pentacam in measuring central corneal thickness (CCT) and anterior chamber depth (ACD) have been rigorously tested (Barakana et al, 2005). Several studies report that the Pentacam has excellent reliability in measuring CCT and ACD in normal and keratoconus populations. The repeatability of posterior corneal elevation was also reported in a recent publication (Chen and Lam, 2007).
The Pentacam allows fast, noncontact examination of the anterior eye segment while the patient is sitting in front of the camera, thus providing good patient comfort and preventing application of local anesthetics and corneal erosions. However, patients have to be able to fixate while the measurement is being made, which can be a problem for children, older patients or patients with nystagmus. (Rufer et al, 2005).
The Pentacam (Oculus, Inc., Lynnwood, Wash., USA) utilizes Scheimpflug imaging. It is a rotating Scheimpflug camera that provides 50 Scheimpflug images during one scan in less than 2 seconds with 500 true elevation points per image. The Pentacam has two integrated cameras. One is located in the center for the purposes of detection of the size and orientation of the pupil, and to control fixation. The second is mounted on the rotating wheel to capture images of the anterior segment. The Scheimpflug image is a complete picture from the anterior surface of the cornea to the posterior surface of the lens.
The slit images are photographed on an angle from 0 to 180 degrees to avoid shadows from the nose. It generates 25,000 true elevation points for each surface, including the center of the cornea. Possible eye movements are captured and corrected internally (Gerste, 2004).
The Pentacam rotating Scheimpflug camera is useful for screening patients because important parameters, especially chamber angle in different positions, ACD, pachymetry, corneal radii and diameter and lens position can be evaluated in examination within a very short period with good reliability (Devereux et al, 2000).