Study questions accuracy of post-PKP IOP measurements with new transpalpebral tonometer

The authors of this study compared IOP measurements taken with Goldmann tonometry (GT, Haag-Streit, Koeniz, Switzerland), the Tonopen XL (Reichert, Inc., Depew, N.Y.) and the new transpalpebral tonometer, TGDc-01 (Ryazan State Instrument-Making Enterprise, Ryazan, Russia), in 43 patients (45 eyes) that had undergone penetrating keratoplasty (PK). They found closer agreement between GT and Tonopen (correlation coefficient 0.84) than between GT and TGDc-01 (correlation coefficient 0.71). The TGDc-01 yielded lower IOP reading than the other two devices.

Mean IOP was 19.22 mm HG with GT, 19.64 mm HG with Tonopen and 16.02 mm HG with TGDc-01. Two-way analysis of variance between the means showed no significant differences between measurements taken with the three devices. IOP measured higher with all tonometers in eyes with greater central corneal thickness.

The authors said it was unclear whether the TGDc-01 was inaccurate or whether avoiding contact with the corneal graft by measuring IOP through the eyelid enables it to provide more accurate IOP readings than those obtained by other methods. The study's results support the view that Tonopen is a helpful tool for measuring IOP when GT is not available.