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Kenneth Yau, Wai H. Chan, I Chris Lloyd, Jane Ashworth, Susmito Biswas; The Accuracy Of Intraocular Pressure Measurement With The iCARE Tonometer. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5072.
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To evaluate the difference between intraocular pressure (IOP) measurements in children using the iCARE tonometer (iT) and either applanation (AT), pneumatic (PT) or digital tonometers (TT).
We carried out a randomised prospective trial of children under 16 years attending the paediatric ophthalmology department of Manchester Royal Eye Hospital. Children had IOP measured twice, once with an iT and again with either a TT, a PT or by AT during the same clinic appointment. Patients with known anatomical distortion of the corneas precluding AT measurement were excluded.
46 children were studied, mean age was 53 months (Range: 2-144). 92 eyes were included. 10 eyes had anterior segment pathology (ASP), defined as either aniridia, congenital glaucoma or Peters’ anomaly. 2 eyes were seen for post operative checks having had a lensectomy and 1 eye had chronic uveitis.Regardless of presence or absence of ASP, total Mean difference (MD), Range (R), Positive Bias (PB) and Limits of Agreement (LOA) between iT and other instruments were as follows: AT: MD=3.2, R=0-8), PB=2.9, LOA=-1.0 to 6.9; TT: MD=2.6, R=0-6), PB=0.9, LOA=-1.8 to 3.5; AT: MD=1.4, R=-3-5), PB=1.6, LOA=-4.2 to 7.3. In eyes with ASP, iT comparisons with PT was as follows: MD=3.9, R=0-8), PB=3.9, LOA=-0.9 to 8.8.
In children with ASP, IOP measured with iT is higher than expected when compared to other tonometers, in some cases by up to 8mmHg. We found an overestimation of IOP in children using the iT with a positive bias of 4mmHg. We propose that IOP measurements taken with the iT overestimates the IOP in children compared with other standard tonometers. Further work should be carried out on a much larger cohort to establish a suitable correction factor for such children.
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