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D. C. Pye, T. Chan, S. Kim, L. Li, R. Lin; The Effect of Contact Lens Induced Oedema on the Accuracy of Goldmann Tonometry in a Mature Population. Invest. Ophthalmol. Vis. Sci. 2008;49(13):690.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the effect of contact lens induced corneal oedema on the accuracy of Goldmann tonometry measurements of intraocular pressure in mature subjects.
Sixteen healthy subjects aged between 50 and 60 years of age were recruited. Corneal curvature, IOP and central corneal thickness (CCT) were measured before and after one hour of monocular closed eye wear of a thick hydroxyethylmethacrylate (HEMA) contact lens. Measurements were then repeated at 20 minute intervals for one hour after lens removal.
Both CCT (+35.0 ± 8.8 microns) and IOP (+2.4 ± 1.2 mmHg) increased significantly after lens wear (p<0.001, paired t test). There was no correlation between the IOP increase and the increase in CCT on lens removal. Whilst the IOP results had returned to the pre lens wear values at 40 minutes after lens removal, the CCT was still significantly thicker than baseline 60 minutes after lens removal (+24.1 ± 9.3 microns, p<0.001, paired t test).
A relatively small increase in CCT from contact lens induced corneal oedema caused an overestimation error in Goldmann tonometry measurements of IOP in healthy mature subjects. The results also seem to suggest that in mature subjects, during corneal deswelling, Goldmann tonometry results can return to baseline values although the cornea is still significantly swollen.
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