Comparison of intraocular tonometry using three different non-invasive tonometers in children.
BACKGROUND
In childhood glaucoma, the correct determination of intraocular pressure (IOP) is crucial in clinical decision-making. We therefore investigated how intraocular tonometry readings correlate with readings from commonly used tonometers.


METHODS
IOP was measured unilaterally in 20 children suffering from congenital (n = 7) or secondary glaucoma (n = 13), 10 minutes after the induction of general anaesthesia. The children were aged from 1 month to 17 years (mean age 4.3 years, median age 1.3 years). Non-invasive applanation (Tono-Pen XL, Perkins tonometer) and indentation tonometry (Schiötz tonometer) were performed in random order prior to intraocular tonometry with a 26-gauge needle connected to a pressure sensor. Linear regression analysis and the coefficients of variance (CV) were used to compare the data obtained from the various tonometers.


RESULTS
Compared with intraocular pressure, the CV was 10% for the Tono-Pen XL, 17% for the Schiötz, and 19% for the Perkins tonometer. The coefficient of determination (r(2)) was 0.74 for Tono-Pen XL, 0.60 for Schiötz and 0.78 for Perkins tonometry. The IOP values obtained with the Tono-Pen XL scattered homogeneously around the intraocular IOP, while the Perkins and Schiötz tonometers underestimated intraocular measured IOP.


CONCLUSIONS
Of the three tonometers evaluated in this series of paediatric glaucoma patients, the Tono-Pen XL most closely reflected true IOP.
University Eye Hospital Freiburg, Killianstrasse 5, 79106 Freiburg im Breisgau, Germany. julia.lasseck@uniklinik-freiburg.de
Julia
J
Lasseck
Thomas
T
Jehle
Nicolas
N
Feltgen
Wolf Alexander
WA
Lagrèze
D000293:Adolescent; D000768:Anesthesia, General; D002648:Child; D002675:Child, Preschool; D005901:Glaucoma / Q000151:congenital / Q000175:diagnosis* / Q000209:etiology; D006801:Humans; D007223:Infant; D007429:Intraocular Pressure; D011446:Prospective Studies; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation* / Q000592:standards*