Description

Standard keratometry measures the radius of corneal curvature and then converts the radius into dioptric corneal power. Computerized corneal topography is performed using various methods, including Placido disc analysis and rasterstereography. These techniques project an image onto the cornea, most commonly a series of concentric rings, and analyze the reflection to determine corneal curvature. They can provide information on anterior corneal power and regularity. Simulated keratometry readings can be generated and the results can be represented in graphical formats, such as a variety of color maps.

Corneal tomography, the computerized reconstruction of multiple images of cornea, can give detailed information about the anterior and posterior corneal curvatures as well as corneal thickness. These techniques include scanning slit, rotating Scheimpflug photography, and anterior segment OCT-based systems. Scanning slit and rotating Scheimpflug imaging are particularly helpful in imaging posterior corneal elevation. Rotating Scheimpflug photography and anterior segment OCT can image corneal and anterior segment anatomy.

Uses in Ophthalmology

Detecting irregular astigmatism secondary to keratoconus, pellucid marginal degeneration, corneal surgery, corneal trauma, and contact lens warpage; evaluating depth of opacities in inherited corneal dystrophies and corneal scars from inflammatory or infectious etiologies. Has the ability to image normal and abnormal corneal and anterior segment structures. It may be helpful in identifying the cause of decreased vision in patients with no known cause. It is useful for refractive surgical screening and imaging the postkeratorefractive cornea. Serial imaging is critical in the evaluation of progression of corneal ectasias.