Corneal thickness measurements with contact and noncontact specular microscopic and ultrasonic pachymetry

Am J Ophthalmol. 2001 Oct;132(4):517-21. doi: 10.1016/s0002-9394(01)01109-6.


Purpose: To evaluate the central corneal thickness values in normal and postkeratoplasty corneas with the new Topcon SP-2000P noncontact specular microscopic, contact specular microscopic, and the "common standard" ultrasonic pachymetry.

Methods: Central corneal thickness was determined in 119 eyes of 81 patients (73 normal eyes of 44 patients and 46 eyes after penetrating keratoplasty) first with a noncontact specular microscopic (Topcon SP-2000P; Topcon Corporation, Tokyo, Japan), then an ultrasonic (AL-1000; Tomey, Erlangen, Germany), and finally with a contact specular microscopic (EM-1000; Tomey, Erlangen, Germany) pachymetry two times each by the same investigator.

Results: Reliability of the central corneal measurements was equally high both in normal and in postkeratoplasty corneas with all of the instruments (Cronbach alpha = 0.99). Noncontact specular microscopic corneal thickness determination correlated significantly both with ultrasonic (r =.86, P <.0001) and contact specular microscopic pachymetry (r =.62, P <.0001). The ultrasonic pachymetry correlated well with the Tomey pachymetry (r =.69, P <.0001). The Topcon normal mean central corneal thickness value (542 +/- 46 microm) was 28 +/- 4 microm lower (P <.0001) compared with the ultrasonic data (570 +/- 42 microm), which was 68 +/- 1 microm lower (P <.0001) compared with Tomey thickness (638 +/- 43 microm).

Conclusions: Central corneal thickness measurements with noncontact specular microscopic, contact specular microscopic, and ultrasonic pachymetry demonstrate that each of the instruments is reliable but cannot be simply used interchangeably.

Publication types

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

MeSH terms

  • Aged
  • Anthropometry
  • Cornea / anatomy & histology*
  • Cornea / diagnostic imaging
  • Diagnostic Techniques, Ophthalmological / standards*
  • Humans
  • Keratoplasty, Penetrating*
  • Microscopy / methods
  • Middle Aged
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Ultrasonography