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October 2004


Applanation tonometry in silicone hydrogel contact lens wearers

R.J. Allen1, D.De Wit12, G.Saleh3, 4
1Essex County Hospital, Colchester, United Kingdom; 2Institute Of Ophthalmology, London, United Kingdom; 3Institute of Ophthalmology, London, United Kingdom; 4Princess Royal University Hospital, London, United Kingdom.


To investigate the accuracy of intraocular pressure (IOP) measurements through a therapeutic silicone hydrogel contact lens using applanation tonometry.

In a cohort study the IOP was measured with a Goldmann applanation tonometer without a contact lens and then repeated with a –0.50DS Bausch and Lomb Purevision silicone hydrogel contact lens in situ, this lens power is commonly used as a bandage contact lens.
Goldmann tonometry, proxymetacaine and fluorescein mixed single use vials, utilising the same tonometer, slit lamp and operator on every occasion to standardize testing.

The IOP of twenty eyes of ten volunteers with no ocular pathology was measured (age range 21-48). The mean difference (±SD) found between IOP measurement with (mean 15.55 ±1.70mmHg) and without (mean 16.05 ± 1.90mmHg) contact lens was found to be –0.5 ± 0.89mmHg. Analysis was performed which revealed a correlation coefficient of 0.89. No significant statistical difference was found between the two groups with paired t-test (p=0.19).

Accurate measurement of IOP by applanation tonometry can be achieved through a silicone hydrogel contact lens.

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