Intraocular pressure measurement after penetrating keratoplasty: minified Goldmann applanation tonometer, pneumatonometer, and Tono-Pen versus manometry

Abstract

The accuracy of intraocular pressure measurement with the minified Goldmann applanation tonometer, the pneumatonometer, and the Tono-Pen tonometer were compared in post-mortem human eyes which had undergone penetrating keratoplasty. Enucleated post-mortem human eyes underwent same sized (7.75 mm) or 0.5 mm oversized (8.25 mm) autologous penetrating keratoplasty. Intraocular pressure was then set and measured manometrically while being determined successively with each tonometer over the range of 0-65 mm Hg. Linear regression analysis comparing tonometric and manometric readings showed: (1) minified Goldmann applanation tonometer-slope 0.985 and 0.944, intercept 1.64 and 2.55 mm Hg, correlation coefficient 0.99 and 0.99 in same sized and oversized grafted eyes respectively; (2) pneumatonometer-slope 1.008 and 0.990, intercept 3.37 and 3.69 mm Hg, correlation coefficient 0.99 and 0.98; (3) Tono-Pen-slope 1.061 and 1.002, intercept 5.01 and 4.06 mm Hg, correlation coefficient 0.97 and 0.98. We concluded that the minified Goldmann applanation tonometer is as accurate or more accurate than the pneumatonometer and the Tono-Pen in post-mortem post-keratoplasty human eyes, and may be an economical, convenient alternative to the latter two instruments in clinical practice.