Wiederhold C., Knorrn M., Gießler S., Duncker G.I.W., Wilhelm F.

Department of Ophthalmology of the Martin-Luther-University Halle- Wittenberg, Magdeburger Str. 8, 06097 Halle, Germany

Background: The aim of this study was a comparison between the results obtained from ultrasound pachymetry or optical pachymetry (Orbscan) and of the cutting depth performed during the operation with the Deutschmann trephine in penetrating keratoplasty. Material and methods: The corneal thickness was determined by means of ultrasound pachymetry (Corneo-Gage II) or optical pachymetry (Orbscan) respectively. Four measurements were taken from each of fifteen patients before penetrating keratoplasty. The measurement points were situated on the edge of an 8 mm zone for 3, 6, 9 and 12 o'clock. The cutting depth was selected as a function of the corneal thickness as determined by way of ultrasound or optical measurement.
Results: Pre-operative diagnosis included keratoconus, cornea guttata, pseudophakic bullous keratopathy, Fuchs' dystrophy, and herpes simplex keratitis. A difference was found between the results obtained with ultrasound, and with optical pachymetry. The results obtained with ultrasound pachymetry were found to be slightly higher. The scope of complete trephination was a function of the amount of difference between the prognostic cutting depth and depth adjustment.
Conclusion: When determining the cutting depth for keratoplasty the corneal thickness determined through ultrasound or optical pachymetry should be considered similar to lamellar refractive operations.

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