Abstract
Purpose :
Although it is widely accepted that the Icare Pro rebound tonometry (RT) and Tono-Pen XL tonometry (TP) readings have good agreement in normal range of intraocular pressure (IOP), it remains unclear whether the IOP readings obtained with these tonometers have a similar relationship in eyes with severely elevated IOP. We performed this prospective observational study to compare the IOP measurements obtained using RT with TP in angle closure eyes with elevated IOP and to compare the RT and TP measurements in the same eyes after subsequent IOP reduction with medical therapy.
Methods :
Angle closure glaucoma eyes with IOP greater than 30 mmHg as measured by Goldmann applanation tonometry (GAT) at the initial examination were enrolled for a prospective study. IOP was sequentially measured by RT, TP and GAT 5 minutes apart. Central corneal thickness (CCT) was measured using a specular microscope. When the GAT-IOP was reduced to below 25 mmHg with medical therapy, RT, TP, GAT and CCT measurements were taken in the same eyes in the same order. We compared the IOP readings between different tonometry methods at baseline and after the IOP-lowering therapy.
Results :
At baseline examination, the mean GAT (50.4±8.9 mmHg) did not differ from the mean RT (50.8±10.9 mmHg, p=0.794), whereas it was significantly lower than the mean TP (44.0 ± 10.3 mmHg, p<0.001). The mean post-treatment IOP was 15.2±4.3 mmHg by RT, 14.3 ± 4.6 mmHg by GAT and 14.3±4.6 mmHg by GAT (all P>0.05). The mean CCT showed no significant difference after the IOP-lowering therapy (542.2±37.3 μm vs 549.7±40.6 μm, p=0.064).
Conclusions :
Unlike the RT, the TP significantly underestimated IOP values compared with GAT in eyes with GAT-IOP exceeding 30 mmHg. Tonometers may have different inter-device relationships in different ranges of IOP. Clinicians need to consider such differences when measuring IOPs in a high range of IOP.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.