May 2004
Volume 45, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2004
Corneal pachymetry by opitcal coherence tomography and by ultrasound. A comparison.
Author Affiliations & Notes
  • R.P. Stodtmeister
    St. Elisabeth Krankenhaus Rodalben, Private Practice, Pirmasens, Germany
  • Footnotes
    Commercial Relationships  R.P. Stodtmeister, 4optics, Luebeck (Germany C, R.
  • Footnotes
    Support  none
Investigative Ophthalmology & Visual Science May 2004, Vol.45, 4494. doi:
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      R.P. Stodtmeister; Corneal pachymetry by opitcal coherence tomography and by ultrasound. A comparison. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4494.

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Abstract

Abstract: : Purpose: Central corneal thickness is a risk factor for glaucoma damage of the optic nerve head according to the results of the Ocular Hypertension Treatment Study. The most widely used method of measurement is ultrasound pachymetry. Its mean values in healthy caucasian subjects vary in published studies from 537µm to 578 µm. This variation may be attributed to differences in the examination techniques in spite built in algorithms of error detection. In this study we compare the results of ultrasound pachymetry with the results of pachymetry by optical coherence tomography. Methods: Ultrasound pachymetry was done by Pachette 500 (DGH Technology). The speed of sound was adjusted at 1640 m/sec. The probe was applied perpendicularly to the center of the cornea. One measurement was taken from each eye. All measurements were done by only one physician. Pachymetry by optical coherence tomography was done by the instrument of the 4optics company (Luebeck, Germany). The instrument allowed a measurement only when the measurement was done in the center of the cornea. One measurement was taken from each eye. The measurements were done by different staff members. The optical coherence measurement was done first. Results: The arithmetic means and the standard deviation and median (minimum; maximum) for optical coherence pachymetry (OCP) and for ultrasound (US) are given in the table. 

Conclusions: The ultrasound method gives higher values of central corneal thickness which are comparable with those of a previous study done with the same instrument. The standard deviation is smaller by 6 µm in the right eyes and by 4 µm in the left eyes. This observation indicates that the measurement by optical coherence tomography is more precise than by ultrasound. The reason is seen in the integrated aiming and fixation control device of the optical coherence instrument. The fact that the ultrasound probe is handheld may add some uncertainty to the results even if the measurements are done by only one examiner. The task of pachymetry may be delegated by applying optical coherence tomography without loss of accuracy.

Keywords: clinical (human) or epidemiologic studies: systems/equipment/techniques • intraocular pressure • cornea: clinical science 
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