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

https://doi.org/10.1016/S0002-9394(01)01109-6Get rights and content

Abstract

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 μm) was 28 ± 4 μm lower (P < .0001) compared with the ultrasonic data (570 ± 42 μm), which was 68 ± 1 μm lower (P < .0001) compared with Tomey thickness (638 ± 43 μm).

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.

Section snippets

Methods

Central corneal thickness was determined in 119 eyes of 81 patients (73 normal eyes of 44 patients, mean age 66 ± 18 years and 46 penetrating corneal grafts of 37 patients, mean age 52 ± 18 years) as a part of routine clinical examination at the Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany. In the following sequence noncontact specular microscopic (Topcon SP-2000P; Topcon Corporation, Tokyo, Japan), ultrasonic (AL-1000; Tomey, Erlangen, Germany), and contact

Results

Reliability of central corneal thickness measurements was comparable in normal and in postkeratoplasty corneas with all of the tested instruments (alpha = 0.99).

Noncontact specular microscopic corneal thickness determination correlated significantly both with ultrasonic (r = .86, P < .0001; Figure 1) and contact specular microscopic pachymetry (r = .62, P < .0001; Figure 2). Likewise, the ultrasonic pachymetry correlated well with the Tomey pachymetry (r = .69, P < .0001; Figure 3).

The mean

Discussion

Earlier studies proved that slit-lamp mounted optical thickness determination compared with specular microscopic and ultrasonic pachymetry disclosed higher interobserver variations, less reproducibility, and provided subjective measurements in healthy subjects.16, 17, 18

Recently, a wide range of new and sophisticated instruments has been developed for the determination of corneal thickness, such as the different optical laser interferometers,19, 20, 21 confocal microscope,22, 23 ultrasonic

References (30)

  • J.J Pole et al.

    Central corneal thickness of patients with dry eyes

    J Am Optom Assoc

    (1985)
  • Z Liu et al.

    Corneal thickness is reduced in dry eye

    Cornea

    (1999)
  • L.I Larsson et al.

    Structure and function of the corneal endothelium in diabetes mellitus type I and type II

    Arch Ophthalmol

    (1996)
  • J.S Saini et al.

    In vivo assessment of corneal endothelial function in diabetes mellitus

    Arch Ophthalmol

    (1996)
  • J Nissen et al.

    A clinical comparison of optical and ultrasonic pachometry

    Acta Ophthalmol Scand

    (1991)
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    This study was supported by the Hungarian Eötvös Fellowship, Ministry of Education, Budapest, Hungary, and the Gertrude Küsen-Stiftung, Hamburg, Germany.

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