Effect of the silicone hydrogel contact lenses on iop measurement

Resumo

Purpose: Silicone hydrogel contact lenses (SHCL) have been used as therapeutic contact lenses (TCL) that have to remain on the eye during long time. Those patients may request an intraocular pressure (IOP) measurement, but it is not desirable to remove the CL. Although there are many reports that evaluate IOP measurements through conventional hydrogel CL, few reports have been published according SHCL. So, the purpose of this study was to evaluate the accuracy of IOP measurements through SHCL lotrafilcon A. Material and methods: 20 healthy subjects (10 men and 10 female) of age between 22 and 34 years were enrolled in the study. Right eye (RE) of each patient was measured by the Perkins aplanation tonometer and the Tono-Pen XL® without CL and then with SHCL lotrafilcon A. Conventional procedure was performed when IOP was determined without CL (fluorescein and anaesthesia for Perkins, and anaesthesia for Tono-Pen XL®), whereas when IOP was measured with CL anaesthesia was avoided for both tonometers, together with fluorescein for Perkins measuremts. Zero hypothesis was evaluated by paired-t test, and 95% limits of agreement (95% LoA) were calculated. Results: No statistical significant differences were found between IOP measurements obtained with CL and without CL for both tonometers (paired-t test; Perkins p = 0.23, Tono-Pen p = 0,17). 95%LoA for Perkins (without CL – with CL) ranged from -3.33 mmHg to +4,43 mmHg, whereas Tono-Pen 95%LoA (without CL – with CL) were from -4.26 mmHg to +3.06 mmHg. 85% of differences were within ± 3 mmHg for Perkins, whereas 95% Tono-Pen differences were within ± 3 mmHg. Conclusions: IOP measurements trough lotrafilcon A CL are accurate and offer an useful alternative to those users who are not allowed to remove the CL for therapeutic treatments and a measurement of IOP is necessary. However, future studies are necessary in order to check theses hypotheses on a population with ocular hypertension.