Goldmann tonometry versus the Tono‐Pen XL for intraocular pressure measurement: an evaluation of the potential impact on clinical decision making in glaucoma

Abstract

To assess the validity of the Tono-Pen XL as an alternative to the Goldmann applanation tonometer (GAT) for the measurement of intraocular pressure (IOP) in patients with ocular hypertension (OHT) and glaucoma. Over a 3 month period, patients with OHT or glaucoma attending a general clinic had IOP measurements taken using the Tono-Pen XL and the GAT. Tono-Pen measurements were taken by suitably trained nursing staff, while Goldmann tonometry was performed by the examining ophthalmologist. There were 124 eyes of 62 patients in this study. Overall, mean IOP was 18.3 +/- 4.8 mmHg using GAT and 18.8 +/- 5.5 mmHg using the Tono-Pen. Using the Bland-Altman method, the upper and lower limits of agreement between the two devices were +10.6 mmHg and -9.6 mmHg, respectively. Significant over- and under-estimates of IOP were noted in 10 (16%) patients. Our findings suggest that the Tono-Pen XL cannot be used as a substitute for GAT in the management of patients with glaucoma or OHT.