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S. Rai, M.R. Moster, M. Kesen, A. Helbe, J. Fontanarosa, R. Wilson, J. Myers, J. Henderer, W. Steinmann; Preview of ProviewTM – Evaluation of the Home Tonometer . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4346.
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Purpose: This study was designed to evaluate the Proview (Pressure Phosphene Tonometer - PPT) in terms of (i) accuracy (ii) patient’s performance and (iii) patient’s perception of glaucoma control. Methods: A 10-month randomized prospective clinical trial was undertaken at Wills Eye Hospital. A total of 135 consecutive patients with glaucoma were included. Intraocular pressure (IOP) was measured with PPT and Goldmann Applanation Tonometry (GAT) by experienced staff (masked throughout the study) and by patients, during office visits. Patients in the treatment group measured their IOP at home with PPT, three times a day for 4-8 weeks. Control patients underwent routine follow-up visits. The primary outcome measure was agreement of Proview IOP measurements with GAT, performed by experienced examiners, on multiple occasions and at different times. The secondary outcome measures included patient’s perception of performance (ease of use and time to learn the technique) and anxiety about glaucoma. Relationship between demographic variables and other associations were also studied. Results: The absolute mean difference between GAT and PPT individual readings was 3.8 ± 3.3 mmHg with a median value of 2.75 mmHg. Overall, 4% of PPT agreed exactly with GAT; 20.5% were within 1mmHg (27.9% higher, 51.6% lower); 34.4% were within 2mmHg (24.6% higher, 41.0% lower); 65.6% were within 4mmHg (11.5% higher, 23.0% lower) and 79.5% were within 6mmHg (6.6% higher, 13.9% lower) of the GAT readings. In the group of patients with IOP between 10 mmHg and 20 mmHg, the absolute mean difference between GAT and PPT was 2.5 ± 1.8 mmHg. In patients with IOP<10 mmHg or >20 mmHg, the absolute mean difference between GAT and PPT individual readings was 7.4 ± 3.8 mmHg. Eighty-seven percent of the patients found PPT easy to use and learned the technique within 4 days, but had no change in their perception of glaucoma management compared to controls. Conclusions: Proview Tonometry is easily performed and accepted by patients. There is considerable variation among patients as to how accurate and consistent their readings are compared to Goldmann Applanation Tonometry. Patients with IOP between 10 mmHg and 20 mmHg had the closest association between PPT and GAT measurements, whereas patients with IOP < 10 mmHg or IOP > 20 mmHg had the greatest number of inaccuracies in the readings. Physicians using the Proview for home-monitoring of IOP will need to verify the accuracy of PPT readings for individual patients.
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