Comparison of anterior segment measurements by 3 Scheimpflug tomographers and 1 Placido corneal topographer

J Cataract Refract Surg. 2011 Sep;37(9):1679-85. doi: 10.1016/j.jcrs.2011.03.055.


Purpose: To compare the anterior segment measurements provided by 3 Scheimpflug tomographers and a Placido corneal topographer.

Setting: Private clinical ophthalmology practice.

Design: Evaluation of diagnostic test or technology.

Methods: In a sample of 25 consecutive patients having either refractive or cataract surgery, the anterior eye segment was analyzed by means of a rotating Scheimpflug camera (Pentacam), 2 devices with a Scheimpflug camera combined with a Placido disk (Sirius and TMS-5), and a Placido disk corneal topographer (Keratron). Measurement results were compared using analysis of variance. Agreement was assessed using Bland-Altman plots.

Results: The mean simulated keratometry (K) was different between the 4 instruments (P<.0001), with Keratron providing the highest value (44.43 diopters [D] ± 1.28 [SD]). The Pentacam and Sirius provided the lowest values (44.05 ± 1.21 D and 44.05 ± 1.27 D, respectively), without statistical difference (posttest). The mean posterior corneal power and minimum corneal thickness were statistically different between the 3 Scheimpflug cameras (P<.0001 and P=.0210, respectively); 95% limits of agreement, however, were narrow for posterior corneal power and large for corneal thickness. The only 2 devices measuring the distance between the corneal endothelium and the anterior lens surface showed a statistically but not clinically significant difference (2.90 ± 0.48 mm and 2.94 ± 0.47 mm, respectively). There were no statistically significant differences in anterior corneal asphericity between the 4 instruments.

Conclusion: Although the measurements of some parameters by different instruments were similar, caution is warranted before using them interchangeably.

Publication types

  • Comparative Study

MeSH terms

  • Anterior Eye Segment / pathology*
  • Biometry / instrumentation
  • Cataract Extraction
  • Corneal Surgery, Laser
  • Corneal Topography / instrumentation*
  • Corneal Topography / standards
  • Endothelium, Corneal / pathology
  • Humans
  • Lens, Crystalline / pathology
  • Middle Aged
  • Photography / instrumentation*
  • Photography / standards
  • Prospective Studies
  • Reproducibility of Results
  • Tomography / instrumentation