Introduction: Point-of-care ocular ultrasound (US) is a valuable tool for the evaluation of traumaticocular injuries. Conventionally, any maneuver that may increase intraocular pressure (IOP) isrelatively contraindicated in the setting of globe rupture. Some authors have cautioned against theuse of US in these scenarios because of a theoretical concern that an US examination may causeor exacerbate the extrusion of intraocular contents. This study set out to investigate whether ocularUS affects IOP. The secondary objective was to validate the intraocular pressure measurementsobtained with the Diaton® as compared with standard applanation techniques (the Tono-Pen®).
Methods: We enrolled a convenience sample of healthy adult volunteers. We obtained thebaseline IOP for each patient by using a transpalpebral tonometer. Ocular US was then performedon each subject using a high-frequency linear array transducer, and a second IOP was obtainedduring the US examination. A third IOP measurement was obtained following the completionof the US examination. To validate transpalpebral measurement, a subset of subjects alsounderwent traditional transcorneal applanation tonometry prior to the US examination as a baselinemeasurement. In a subset of 10 patients, we obtained baseline pre-ultrasound IOP measurementswith the Diaton® and Tono-Pen®, and then compared them.
Results: The study included 40 subjects. IOP values during ocular US examination were slightlygreater than baseline (average +1.8mmHg, p=0.01). Post-US examination IOP values were notsignificantly different than baseline (average -0.15mmHg, p=0.42). In a subset of 10 subjects, IOPvalues were not significantly different between transpalpebral and transcorneal tonometry (average+0.03mmHg, p=0.07).
Conclusion: In healthy volunteer subjects, point-of-care ocular US causes a small and transientincrease in IOP. We also showed no difference between the Diaton® and Tono-Pen® methodsof IOP measurement. Overall, the resulting change in IOP with US transducer placement isconsiderably less than the mean diurnal variation in healthy subjects, or pressure generated byphysical examination, and is therefore unlikely to be clinically significant. However, it is important totake caution when performing ocular ultrasound, since it is unclear what the change in IOP would bein patients with ocular trauma. [West J Emerg Med. 2015;16(2):263–268.]