Intraocular Pressure Measurement with Pneumatonometry and a Tonometer Tip Cover

Abstract

Purpose: To investigate the precision and accuracy of IOP measurements using a pneumatonometer and a tonometer tip cover (Tono-Pen Ò tip cover) acting as a membrane between a cadaver eye model and pneumatonometer probe. Methods: A total of 480 paired IOP measurements, with and without a Tono-Pen cover, were collected across 4 pressure levels of 7, 10, 20 and 30 mmHg. IOP measurements were obtained by three different pneumatonometer units paired with three different masked operators (three configurations). Four eyes were sampled for each eye pressure level. The sequence of eye pressure, configuration, and measurements with vs. without the Tono-Pen cover was randomized. Results: With the Tono-Pen cover in place, there was a negative bias with a mean IOP difference of-1.18 mmHg for all 480 paired samples compared with the measurements absent the cover. Compared with the test pressure settings (i.e., 7, 10, 20, 30 mmHg), the overall mean bias was ? 0.35 mmHg with the Tono-Pen cover present. With the Tono-Pen cover present, the overall repeatability %CV (percent coefficient of variation) was 3.4% and the reproducibility %CV was 3.8% compared with a repeatability %CV of 3.2% and reproducibility %CV of 5.7% without the Tono-Pen cover. Conclusion: Measurement of IOP via pneumatonometry with a Tono-Pen cover in place, also known as the excursion test method, yields precise, accurate and reproducible results. This developed method of pressure measurement is an acceptable and reliable form of IOP measurement.

Short-term Evaluation of Negative Pressure Applied by the Multi-Pressure Dial System to Lower Nocturnal IOP: A Prospective, Controlled, Intra-subject Study

“…The limitations of this study include the small sample size, the single visit, the shortterm duration and the non-randomized design. Measuring IOP using a pneumatonometer and a tonometer tip cover remains a novel method of IOP measurement, and while favorable results regarding the accuracy and precision of the method have been reported in prior clinical work [13], no published benchtop studies have specifically investigated the precision of the method in a benchtop setting with active negative pressure. It remains unclear which effects, if any, the MPD may have over the long term with repeated wear at night for weeks to months.…”

“…The Excursion adaptation of the device contains an access port on each of the lenses that enables a pneumatonometer to make IOP measurements under active negative pressure. Because the negative pressure microenvironment requires a sealed environment, a specialized method of IOP measurement, also known as the excursion test method, was employed, as described in detail in [13]. Of note, the pneumatonometric measurement employed with the Excursion test method occurs across a latex membrane (tono-pen cover) and remains external to the negative pressure microenvironment.…”

Evaluation of the IOP-Lowering Effect of a Multi-Pressure Dial at Different Negative Pressure Settings

“…2), was described in a prior study with favorable results, supporting its use as an accurate and reliable form of IOP measurement. 15 To obtain IOP measurements with the excursion test method, a silicone support tube and Tono-Pen cover is placed within the access port of the goggle lens with the proximal end (containing the Tono-Pen cover)…”

<p>Overnight Safety Evaluation of a Multi-Pressure Dial in Eyes with Glaucoma: Prospective, Open-Label, Randomized Study</p>

“…IOP measurements while negative pressure was active were obtained via the excursion test method, a method previously described in detail that permits IOP measurements while the negative pressure environment is maintained. 12 After the IOP measurements were obtained via the port in the excursion MPD, the device was removed and subjects were sent home with a standard MPD programmed for 10 mmHg negative pressure in the study eye only. Subjects were encouraged to wear the device nightly and were educated on how to use the device and troubleshoot if necessary.…”