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[Comparative study of two portable tonometers: Tono-Pen XL and Perkins]
M T Andrada Márquez1, I Fesser Oroz, A Antón López
1IOBA y Hospital General de Segovia, Universidad de Valladolid, España.
Purpose:
To evaluate the reproducibility of two portable tonometers and to compare the intraocular pressure (IOP) measurements obtained with both instruments taking into account the level of experience of the examiner with this technique.
Method:
Cross-sectional study. IOP was measured in 35 eyes of 35 normal subjects and 20 eyes of 20 ocular hypertensive patients with Perkins aplanation tonometer and Tono-Pen XL digital tonometer. Five measurements were made with Perkins (by an ophthalmologist) and 10 with Tono-Pen (5 by an ophthalmologist and 5 by a general practitioner).
Results:
Considering the sample as a whole there was no statistically significant difference, and there was a significant correlation between the mean measurements obtained with Perkins tonometer and Tono-Pen and between the mean obtained by doctors with and without previous tonometric experience (p<0.001, ANOVA). Variability of Tono-Pen measurements is greater than the Perkins measurements and it is considerable in both cases (coefficient of variation 7-9%). Tono-Pen measurements tend to show a greater variability in hypertensive subjects, and tend to underestimate high IOP when compared with Perkins measurements. Tono-Pen identified IOP > or =21 mmHg with a sensitivity of 40% and a specificity of 94-97%.
Conclusion:
Tono-Pen allows measurement of IOP to personal with no tonometric experience. There is a strong correlation between measurements obtained with both tonometers. Tono-Pen shows a tendency to underestimate high IOP and offers low sensitivity in detecting IOP greater than 21 mmHg.
