The impact of silicone hydrogel contact lenses on the measurement of intraocular pressure using non-contact tonometry

Aim. To evaluate the effect of spherical silicone hydrogel soft contact lens designs and their power on the measurement value of intraocular pressure (IOP) using non-contact tonometry methods. Methods. We measured the IOP with and without spherical silicone hydrogel soft contact lenses on 143 eyes of 80 subjects who did not have any ocular or systemic diseases. Results. The Wilcoxon statistical analysis test for ranking the average values of IOP (15.81 ± 3,46 mm Hg) measured on n = 143 eyes over a spherical silicone hydrogel soft contact lens showed significantly higher values than with no contact lens (14.54 ± 3.19 mm Hg), Z = -5.224, p = 0.001. Refractive power analysis of the contact lens of -9.00D to +6.00 D showed a significant difference of IOP in the range from 0.00D to -6.00D. Conclusion. Non-contact tonometry is not an accurate method of measuring IOP over spherical silicone hydrogel soft contact lenses which belong to therapeutic contact lenses.