The measurement of intraocular pressure over positive soft contact lenses by rebound tonometry

Accuracy of Intraocular Pressure Measurements of Eyes with Therapeutic Contact Lenses after Vitrectomy

Purpose: To evaluate the accuracy of intraocular pressure (IOP) measurements obtained by a rebound and non-contact tonometer in eyes with a therapeutic contact lens (CL) after vitrectomy.Methods: In 60 eyes of 60 patients who underwent vitrectomy for vitreoretinal disease, IOP was measured using a rebound tonometer (iCare ic200®; IOPRT) and non-contact computerized air puff tonometer (CT-80, IOPNCT), before and after wearing a CL (Purevision2®, +0.0 diopter). The mean IOP of three consecutive measurements were analyzed, and a comparative analysis with IOP measured by a Goldman applanation tonometer (IOPGAT) was performed.Results: The mean IOPRT without and with the CL was 12.55 ± 5.43 and 13.12 ± 5.13 mmHg, respectively, showing a statistically significant difference (p = 0.02) and strong positive correlation (r = 0.90, p < 0.001). The mean IOPNCT with and without the CL was 12.18 ± 3.24 and 12.17 ± 3.14 mmHg, showing no statistically significant difference (p = 0.17). The consistency with IOPGAT (12.57 ± 5.22 mmHg) was highest in IOPRT without the CL, followed by IOPRT with the CL, IOPNCT without the CL, and IOPNCT with the CL (intraclass correlation coefficients = 0.955, 0.945, 0.856, and 0.850, respectively). In addition, the rebound tonometer successfully measured IOP, regardless of whether the CL was worn; however, the non-contact tonometer failed to measure IOP in seven eyes without the CL and nine with the CL. No difference was observed according to intraocular tamponade type.Conclusions: A rebound tonometer can be used as an alternative IOL measuring method in eyes for which it is difficult to use a Goldman applanation tonometer due to the postoperative presence of a therapeutic CL.

Rebound Tonometry over Soft Contact Lenses

Introduction:

Goldmann applanation tonometry (GAT) is named as a gold standard for intraocular pressure (IOP) measurement.

Aim:

To assess the accuracy of intraocular pressure (IOP) measurements using rebound tonometry over hydrogel and silicone hydrogel contact lenses (CLs) of different powers.

Methods:

This study included 117 eyes of 61 patients (12 male, 49 female), all habitual wearers of hydrogel and silicone hydrogel CLs, and none previously diagnosed with glaucoma, ocular hypertension or anterior surface disease. Five IOP measurements were taken over each eye using a rebound tonometer (Icare): with soft CLs in situ and then repeated without CLs. Lens power ranged from -9.50 to +10.00 spherical diopters and to a maximum of -0.75 cylinder diopters.

Results:

A significant positive correlation was found between IOP measurements with and without CLs. The difference between IOP measurements with (mean 20.74±5.19 mmHg) and without (mean 18.79±4.36 mmHg) CLs was found to be 1.95 mmHg (P <0.01). Statistical analysis was performed using the paired t-test and a correlation coefficient was calculated (r = 0.59; P <0.001). We have observed that increase in central corneal thickness (CCT) correlates positively with increase of measurement error of rebound tonometry (r = 0.43; P <0.001).

Conclusion:

We have shown good reliability of IOP measurements over CLs of different materials and thickness profiles while using rebound tonometer which makes it a feasible and accurate method for clinical purposes.