Excursion Tonometry Accurately Evaluates IOP During Negative Pressure Application

Optic disc affected by glaucoma.
An intraocular pressure-lowering goggle system does not affect tonometry readings, a report shows.

Intraocular pressures (IOP) can be accurately measured during negative pressure (NP) application using excursion tonometry, according to results of a study, published in Clinical Ophthalmology.

The Multi-Pressure Dial System (MPD) (Equinox Ophthalmic, Inc.) device is designed to lower IOP by applying NP with specially-designed goggles. This 2-part study evaluated the accuracy of IOP assessment during the NP application process in an open and closed perfusion organ culture (POC) column system. IOP measurement using excursion tonometry was compared with transducer measurement during 13 paired pre-set IOP (10, 20, 25, 30 mm Hg) and NP (0, 5, 10, 15, 20 mm Hg) combination models, for a total of 520 paired open/closed measurements.

During the open system tests, no significant differences between excursion tonometry or transducer were observed. Specifically, at an IOP of 10 mmHg, the excursion tonometry and transducer measured IOP as an average of 10.8±1.4 and 9.8±0.3 mm Hg (P =.378), at 20 mm Hg 20.0±1.5 and 20.2±0.4 mmHg (P =.137), at 25 mm Hg 24.3±1.1 and 24.9±04 mm Hg (P =.279), and at 30 mm Hg 28.1±0.9 and 30.1±0.6 mmHg (P =.294), respectively.

In all 520 paired measurements, the average difference in IOP value was -0.7±1.6 mm Hg.

During the closed system tests, the excursion tonometry and transducer returned similar readings. Excursion tonometry and transducer readings were 10 mm Hg IOP with 0 mm Hg NP (mean, 10.4±1.4 vs 10.1±0.3 mm Hg), 10 mm Hg IOP with -5 mm Hg NP (mean, 7.6±1.1 vs 7.2±0.4 mm Hg), 20 mm Hg IOP with -10 mm Hg NP (mean, 15.9±1.8 vs 14.9±1.2 mm Hg), and 30 mm Hg with −20 mm Hg NP (mean, 30.6±1.4 vs 30.2±0.4 mm Hg), respectively.

In all 520 paired measurements, the mean difference in IOP value was 0.7±1.4 mm Hg.

This study was limited as it was a simulation using a POC system. Results should be confirmed in human models.

The study authors concluded that these findings supported the excursion tonometry method for evaluating IOP during NP application.

Disclosure: This research was supported by Equinox Ophthalmic, Inc. Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.


Brambilla E, Ferguson TJ, Chu N, Ammar D, Yoo P. Intraocular pressure measurement with pneumatonometry and a tonometer tip cover during negative pressure application. Clin Ophthalmol. 2022;16(4):1289-1300. doi:10.2147/OPTH.S359605