New TonoPen XL: comparison with the Goldmann tonometer

Purpose To compare the intraocular pressure (IOP) values obtained using a G oldmann tonometer (Haag-Streit) with those obtained with the new Tonopen XL (Mentor), which has certain differences compared with first- and second-ge neration models. Methods The IOPs of 104 patients were assessed by Goldmann tonometer and To nopen XL tonometer. Goldmann measurements was done first in 145 eyes and To nopen measurements were done first in 53 eyes. Four observers measured the IOP. Observers A, B and C used the Goldmann tonometer first and then the To nopen XL, while observer D used the Tonopen XL first and then the Goldmann tonometer. The results were analysed by descriptive analysis and, when the distribution of the data was normal, paired t-test and Pearson's r coeffici ent were used to compare and correlate IOP measurements between Goldmann an d Tonopen measurements. When the distribution of the data was non-normal, t he Wilcoxon matched-pair test and Spearman coefficient were used. The agree ment between Goldmann and Tonopen values was also calculated. ANOVA test wa s used to compare the difference obtained by 'Goldmann minus Tonopen' measu rements among the three different observers. Results A statistically significant difference (p < 0.0001) was found betwe en the IOP readings obtained by Goldmann tonometer and the Tonopen XL and a significant correlation was found between the Goldmann values and Tonopen XL values (p < 0.001). When the Goldmann IOP was more than 20 mmHg the Tono pen XL measurements were lower than the Goldmann values. Also in this group this difference was statistically significant. No significant difference w as found between Goldmann values and Tonopen values among the three observe rs, even though a significant difference was found between Goldmann values and Tonopen values for observer B. When the values obtained by first the Go ldmann tonometer and then the Tonopen XL were compared with those obtained by first the Tonopen XL and then the Goldmann tonometer, no significant dif ference was found between the two groups. Conclusion The new Tonopen XL provides similar results to the Goldmann tomo meter in 62% of the cases and was slightly less accurate than the Goldmann tonometer for extreme values, just like the previous Tonopen. Nevertheless the precision is good enough for the purpose of adequate screening.