Anterior Segment Imaging and Corneal Topography

Anterior segment imaging is a rapidly advancing field of ophthalmology. New imaging modalities, such as rotating Scheimpflug imaging (Pentacam-Scheimpflug) and anterior segment optical coherence tomography (Visante OCT and Slit-Lamp OCT), have become commercially available. These new modalities supplement the more established imaging devices of Orbscan scanning slit topography and ultrasound biomicroscopy (UBM). All devices provide software that allows quantitative information, as well as, qualitative imaging of the cornea and anterior chamber. They provide quantitative angle estimation by calculating the angle between the iris surface and the posterior corneal surface. Direct angle visualization is also possible with the OCT devices and UBM; they provide images of the scleral spur, ciliary body, ciliary sulcus and even canal of Schlemm in some eyes. Pentacam- Scheimpflug can measure net corneal power, a feature particularly useful for cataract patients having undergone previous corneal surgery. Anterior segment OCT can also measure corneal dimensions and anterior chamber width prior to phakic intraocular lens implantation. Latest findings show it to be useful in the presence of corneal opacities. The arrival of the new imaging devices may herald the dawn of a new era for ophthalmic diagnosis, particularly in view of the ease and non-contact nature of many of the examination modalities.

Keywords: Cornea, Anterior Chamber, Angel Measurements, Anterior Segment OCT, Scanning Slit Tomography, Corneal Topography, Scheimpflug Imaging, Ultrasound Biomicroscopy, Keratometry, Magnetic Resonance Imaging, Computerised Tomography, Placido Ring Topography, Purkinje-Sanson Images, Fourier Domain, Time Domain, pachymetry, Optical Coherence Tomography, Keratoconus, Keratoplasty