Scanning-slit and specular microscopic pachymetry in comparison with ultrasonic determination of corneal thickness

Cornea. 2001 Oct;20(7):711-4. doi: 10.1097/00003226-200110000-00008.


Purpose: To determine the central corneal thickness values in healthy eyes with the recently developed Orbscan scanning-slit system, contact and noncontact specular microscopic pachymetry and compare the results to conventional ultrasonic pachymetry.

Methods: In the following sequence, Orbscan, Topcon SP-2000P noncontact specular microscope, AL-1000 ultrasound, and Tomey contact specular microscope were used to record thickness values. Thirty-four healthy right corneas of 34 healthy subjects were investigated.

Results: Orbscan pachymetry correlated significantly with ultrasound (r = 0.64, p < 0.001), contact (r = 0.45, p < 0.001), and noncontact specular microscopy (r = 0.72, p < 0.001). Likewise, the Topcon SP-2000P noncontact specular microscopy pachymetry disclosed similar statistical results compared with ultrasound (r = 0.88, p < 0.001), and contact specular microscopy pachymetry (r = 0.76, p < 0.001). The mean central corneal thickness results were significantly higher ( p < or = 0.01) than ultrasonic values (580 +/- 43 microm) using the contact specular microscope (640 +/- 43 microm) or Orbscan system (602 +/- 59 microm) but were significantly lower ( p < 0.001) using the noncontact specular microscope (547 +/- 49 microm).

Conclusions: The results indicate that the devices tested cannot be simply used interchangeably. For long-term patient follow-up, one specific instrument is recommended. Recently developed pachymetry machines are especially helpful when additional corneal data such as thickness profile, elevation maps, anterior chamber depth, and endothelial morphology are required.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cornea / anatomy & histology*
  • Cornea / diagnostic imaging
  • Diagnostic Techniques, Ophthalmological*
  • Female
  • Humans
  • Male
  • Microscopy
  • Ultrasonography