Intraocular pressure and photorefractive keratectomy - A comparison of three different tonometers

Purpose. To evaluate the intraocular pressure (IOP) with three different in struments, Goldmann applanation tonometer (GAT), noncontact tonometer, and Tone-Pen after photorefractive keratectomy (PRK) for myopia. Methods. A pro spective case series study to evaluate preoperative and postoperative IOP m easurements of 149 eyes at 12 months. We performed GAT, noncontact tonometr y, Tone-Pen central, and Tone-Pen temporal periphery measurements. We also performed measurements of the central corneal thickness (CCT) by ultrasonic pachymetry and keratometry. Preoperative IOP reading served as control for all studies. Results. After PRK, IOP reading was significantly reduced in the treated eyes when compared with the control measurements (11.87 +/- 1.7 3 vs. 13.37 +/- 1.52 mmHg, p < 0.0001 with GAT; 12.07 +/- 1.6 vs. 13.51 +/- 1.59 mmHg, p < 0.0001 with noncontact tonometer; 12.18 +/- 1.6 vs. 13.48 /- 1.55 mmHg, p < 0.0001 with Tone-Pen central; 13.48 +/- 1.65 vs. 13.71 +/ - 1.56 Hg, p < 0.0104 with Tono-Pen temporal periphery). There was also a s ignificant correlation between IOP reading changes measured by GAT, noncont act tonometer, Tone-Pen central, and change of CCT and between reduction of IOP reading and keratometry (r(2) > 0.39, p < 0.0001 for each). The correl ation between IOP reading change by Tone-Pen temporal periphery and CCT was also significant but r(2) value was only 0.034. Tone-Pen temporal peripher y postoperative IOP measurements had the best correlation with preoperative GAT IOP (r(2) = 0.57, p < 0.0001). Conclusions, PRK reduced IOP reading as measured by GAT, noncontact tonometer, and Tone-Pen central; less so when measured by Tone-Pen temporal periphery. Early detection of glaucoma and IO P follow-up in glaucoma patients may be done best by peripheral Tone-Pen me asurements over the nonablated cornea.