Central and peripheral pressure measurements with the Goldmann tonometer and Tono-Pen after photorefractive keratectomy for myopia

Purpose: To compare the accuracy of Goldmann tonometry with that of the Ton o-Pen((R)) in measuring intraocular pressure (IOP) after photorefractive ke ratectomy (PRK). Setting: Eye Clinic, Cantonal Hospital, Lucerne, Switzerland. Methods: Thirty-five eyes (25 patients) had PRK for a mean myopia of -6.2 d iopters +/- 2.6 (SD). Intraocular pressure (IOP) measurements were performe d first with the Goldmann tonometer and then with the Tone-Pen in 2 corneal locations: centrally in the usual manner and temporally. For the temporal measurements, the patient was directed to gaze nasally as the tonometer was placed perpendicular to the temporal portion of the cornea and with the ri m of the tonometer positioned just inside the limbus of the cornea. Subsequ ently, similar measurements were made with the Tone-Pen. Measurements were performed before and 1 and 3 months after PRK. Results: Preoperative IOPs measured centrally and temporally were similar. After PRK, the central pressure readings with the Goldmann tonometer and th e Tone-Pen were between 1.8 and 2.3 mm Hg lower than those measured tempora lly. The differences were statistically significant (P < .0001). Conclusion: Central corneal pressure readings obtained with either the Gold mann tonometer or the Tone-Pen after myopic PRK are inaccurate. Measurement s over the temporal part of the cornea are likely more reliable. (C) 2000 A SCRS and ESCRS.