Measurements of intraocular pressure by Goldmann tonometry, Tonopen XL, and the transpalpebral tonometer, TGDc-01, after penetrating keratoplasty: a comparativye study.

The aim of this study was to compare intraocular pressure (IOP) measurements obtained by Goldmann tonometry (GT), the Tonopen XL, and a new transpalpebral tonometer, TGDc-01, in eyes that had undergone penetrating keratoplasty (PKP). IOP was measured in post-PKP eyes by means of GT, Tonopen XL, and TGDc-01. Central corneal thickness measurements were also obtained for all eyes. Forty-five eyes of 43 patients were enrolled in the study. The mean IOP difference (+/-SD) was -0.42 +/- 5.83 mm Hg between GT and Tonopen and 3.20 +/- 7.55 mm Hg between GT and TGDc-01. The correlation coefficient was 0.84 between GT and Tonopen XL (P < 0.001) and 0.71 between GT and TGDc-01 (P < 0.001). Overall 2-way analysis of variance between the means showed no significant differences between the 3 devices (P = 0.077). A closer agreement was found between GT and Tonopen XL in post-PKP eyes. TGDc-01 yielded lower IOP readings than the other 2 devices. It remains uncertain whether this new transpalpebral tonometer is simply 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 transcorneal techniques.