Reproducibility of the New Goldmann AT900D Digital Tonometer

Purpose: To examine the reproducibility of the new digital Goldmann applanation tonometer AT 900D (DGT) for measuring intraocular pressure and to compare its readings with those provided by the conventional analog Goldmann tonometer (AGT). Methods: In 3 different sessions (S1, S2, and S3), 3 intraocular pressure measurements were made in 15 eyes of 15 healthy subjects using both the DGT and AGT. The order of use of the tonometers was random and the data were collected by a different examiner to the one taking the measurements. Data were compared by determining coefficients of variation for each session and representing the differences detected as Bland-Altman plots. Results: The mean differences recorded (AGT-DGT) were 0.1, 0.3, and -0.1 for S1, S2, and S3, respectively. None of the differences were significant and none were >= 3 mm Hg. Coefficients of variation were lower in the 3 sessions for the DGT, the difference being significant for S2 and S3 (4.87% vs. 3.99%, P = 0.400; 4.84% vs. 3.55%, P = 0.028; and 5.04% vs. 3.50%, P = 0.025 in S1, S2, and S3 respectively). Conclusions: The new digital Goldmann tonometer shows a high reproducibility and excellent correlation of measures with those of the AGT.