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Abstract
Imaging techniques of the cornea are developing rapidly, mainly because of recent advances in refractive surgery. To understand the significance of new imaging techniques, the relevant principles of corneal optics are reviewed. The discussion of the most common clinical method of Placido-based corneal topography emphasizes important concepts of its clinical interpretation. The principles and clinical significance of several emerging technologies are reviewed in this essay.
The Pentacam actually has 2 cameras. One is for detection and measurement of pupil, which helps with orientation and fixation. The second camera is used for visualization of the anterior segment. The Pentacam is able to image the cornea such that it can visualize anterior and posterior surface topography, including curvature, tangential, and axial maps.
Advantages of the Pentacam include the following: (1) high resolution of the entire cornea, including the center of the cornea; (2) ability to measure corneas with severe irregularities, such as keratoconus, that may not be amenable to Placido imaging; and (3) ability to calculate pachymetry from limbus to limbus. The Pentacam can also provide corneal wavefront analysis to detect higher-order aberrations.