Can Intraocular Pressure Measurements be Used to Screen for Elevated Intracranial Pressure in Emergency Department Patients?

Abstract

BackgroundHandheld measurement of intraocular pressure (IOP) has been previously shown to accurately predict elevated intracranial pressure (ICP) in neurosurgical patients. Handheld tonometry may have clinical utility in the prediction of elevated ICP among a cohort of emergency department (ED) patients receiving lumbar puncture (LP). ObjectiveTo ascertain the sensitivity and specificity of IOP for the prediction of elevated ICP in ED patients undergoing LP. MethodsIn this prospective observational pilot study, all ED patients over the age of 18 years and undergoing LP in the ED for any reason were eligible to participate. Study participants had IOP measured with the Tono-Pen XL (Reichert, Inc., Depew, NY) while in the supine position before LP. OP was measured in the lateral recumbent position. Elevated IOP was defined as≥20mm Hg; elevated ICP was defined as≥20mm H2O. ResultsThere were 82 patients screened and 46 patients enrolled at the time of interim analysis. Of the 46 patients, 32 had a successful LP in the lateral recumbent position. There were 18/32 patients with a successful LP in the lateral recumbent position who had elevated opening pressure; 9/32 patients with a successful LP had an elevated IOP. Furthermore, 4/9 patients with elevated IOP also had an elevated opening pressure. There was only one patient who had elevated IOP, elevated ICP, and diagnostic cerebrospinal fluid (sensitivity 24%, 95% confidence interval [CI] 9–48%; specificity 63%, 95% CI 32–88%; positive predictive value 28%, 95% CI 14–47%; negative predictive value 72%, 95% CI 53–96%). ConclusionsHandheld tonometry has poor sensitivity and specificity for the prediction of increased ICP, and should not be used as a screening tool in the ED.