Intracorneal Ring Segments Workup

Updated: Mar 15, 2016
  • Author: Manolette R Roque, MD, MBA, FPAO; Chief Editor: Michael Taravella, MD  more...
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Imaging Studies

Corneal topography

Corneal topography development provides surgeons with effortlessly understood color-coded maps of corneal curvature in addition to quantitative indexes of irregular astigmatism that correlate with potential visual acuity.

Modern instrumentation produces a videokeratograph, which generally is in the form of a color-coded contour map.

Different manufacturers use different methods (eg, Placido, 40 scanned slits, combination Placido and 40 scanned slits, phase modified laser holography, raster stereography).

The use of video keratography in the preoperative and postoperative evaluation of all patients undergoing refractive surgery is valuable.

Dual Scheimpflug analyzer

This is a high-precision optical system for corneal topography and 3-dimensional analysis of the anterior eye segment, based on a Revolving Dual Channel Scheimpflug Camera and a Placido Disk.

Placido imaging furnishes high accuracy curvature data.

Scheimpflug imaging is optimal for precise elevation data.


Other Tests


The pachymeter (optical, ultrasonic) is used to measure corneal thickness.

Accurate determination of corneal thickness preoperatively allows the surgeon to set the depth of incision to two thirds of the measured result.

Orbscan II by Orbtek uses both 40 scanned slits and Placido methods to provide anterior and posterior corneal curvature in addition to data on corneal thickness.



A manual corneal trephination set to create a corneal tunnel for intrastromal corneal ring segments has been available since the introduction of ICRS. Currently, most femtosecond laser units are able to create similar tunnels using a specific program. The femtosecond laser–created tunnels are more precise and result in less morbidity than the manual approach.