International Journal of Keratoconus and Ectatic Corneal Diseases

Register      Login

VOLUME 1 , ISSUE 3 ( September-December, 2012 ) > List of Articles

RESEARCH ARTICLE

Comparison of Topographic Technologies in Anterior Surface Mapping of Keratoconus using Two Display Algorithms and Six Corneal Topography Devices

Cynthia J Roberts, Richard G Lembach, George A Markakis, James W Harris

Citation Information : Roberts CJ, Lembach RG, Markakis GA, Harris JW. Comparison of Topographic Technologies in Anterior Surface Mapping of Keratoconus using Two Display Algorithms and Six Corneal Topography Devices. Int J Kerat Ect Cor Dis 2012; 1 (3):153-157.

DOI: 10.5005/jp-journals-10025-1030

Published Online: 01-12-2014

Copyright Statement:  Copyright © 2012; The Author(s).


Abstract

Purpose

To evaluate anterior surface topographic technologies and display algorithms in mapping keratoconus.

Materials and methods

A total of 27 eyes of 17 subjects clinically diagnosed with keratoconus were imaged on six topographers: EyeSys, Alcon EyeMap, Keratron, TMS-1, Orbscan and PAR corneal topography system. Axial distance (AD) and instantaneous radius of curvature (IROC) algorithms were generated, and the cone apex was determined manually using a cursor. Intermachine comparisons for cone magnitude (steepest curvature), as well as cone location in radius and meridian were performed for each display algorithm using both AD and IROC. Significance (p < 0.05) was determined using repeated measures analysis of variance (ANOVA) on successive mean values. Maps were also evaluated for processability, defined by the ability to reconstruct a reasonable map for each subject, not map quality.

Results

There were no significant differences between successive means for cone location in either radial or meridional directions. For AD, Orbscan was greater than both small mire Placido devices (Keratron and TMS-1), which were not different from each other. The small mire devices had significantly greater curvature magnitude than the large mire placido devices (EyeSys, Alcon EyeMap) which were not different from each other. Finally, PAR was significantly lower than the large mire Placido devices. For IROC, the pattern was the same with the exception that the Orbscan was not different than the small mire Placido devices in curvature magnitude. For processing success, the PAR had 100% processability, and all other devices were between 73 and 77%.

Conclusion

In monitoring keratoconus, evaluation of change over time is fundamental to treatment decisions, making understanding of topographic technology differences in mapping keratoconic corneas extremely important.

How to cite this article

Markakis GA, Roberts CJ, Harris JW, Lembach RG. Comparison of Topographic Technologies in Anterior Surface Mapping of Keratoconus using Two Display Algorithms and Six Corneal Topography Devices. Int J Kerat Ect Cor Dis 2012;1(3):153-157.


PDF Share
  1. Tangential vs sagittal videokeratographs in the ‘early’ detection of keratoconus. Am J Ophthalmol 1996; 122:887-89.
  2. Keratoconus. Surv Ophthalmol 1998 Jan-Feb;42(4):297-319.
  3. Review of past and present techniques of measuring corneal topography. Opthal Phys Opt 1994 Jan;14:49-58.
  4. Enigma of the corneal contour. CLAO J 1992 Oct;18:267-73.
  5. Characterization of the inherent error in a spherically- biased corneal topography system in mapping a radial aspheric surface. J Refrac Corneal Surg 1994 Mar-Apr;10:103-16.
  6. Analysis of the inherent error of the TMS-1 topographic modeling system in mapping a radially aspheric surface. Cornea 1995;14(3):258-65.
  7. PAR corneal topography system (PAR CTS): The clinical application of close-range photogrammetry. Opt Vis Sci 1995;72(11):828-37.
  8. Corneal topography using computer analyzed rasterstereographic images. Appl Opt 1988;27(6):1135-40.
  9. Corneal topography: The state of the art. New Jersey (Thorofare): Slack Incorporated 1995;89-120.
  10. Accuracy of corneal elevation with four corneal topography systems. J Ref Surg 1998;14(2):100-04.
  11. Corneal topography: A review of terms and concepts. J Cat Refr Surg 1996 Jun;22:624-29.
  12. Axial and instantaneous power conversion in corneal topography. Invest Ophthalmol Vis Sci 1995;36:2155-59.
  13. Comparison of Placido, Scheimpflug, and combined dual Scheimpflug-Placido technologies in evaluating anterior and posterior CLMI, SimK's, as well as Kmax, in keratoconic and post refractive surgery ectasia. Int J Kerat Ectat Corn Dis 2012;1(1):44-52.
PDF Share
PDF Share

© Jaypee Brothers Medical Publishers (P) LTD.