Ocular pulse amplitude test detects stroke risk

Zurich, Switzerland-Ophthalmologists someday may perform ocular pulse amplitude (OPA) tests during routine eye exams to identify patients who are at high risk for stroke, according to researchers at the University of Zurich, Switzerland.

The test can reliably detect symptomless carotid artery stenosis (CAS), a condition that is a known risk factor for stroke. Researchers found that patients who had the lowest OPA scores also had the most seriously blocked arteries. The study is published in the June issue of Ophthalmology.

The investigators used a dynamic contour tonometer to check the OPA of 67 patients who were assumed to have CAS. After measuring the IOP levels, the tonometer computes the patient’s OPA score by finding the difference between the IOP levels that occur during the systolic and diastolic heartbeats.

When blood flow to the eye is blocked by CAS, not much difference exists between the two pressure levels, so the OPA score is low. The researchers used ultrasound exams to corroborate that each study participant had CAS and to detail the severity of his or her blockage.

“Our results show that OPA is a reliable, safe screening test for CAS,” said lead researcher Pascal Bruno Knecht, MD. “We recommend further study to confirm the value of using OPA to detect and assess the severity of CAS and to define its use in stroke prevention.”

Ophthalmologists already using a dynamic contour tonometer to screen for glaucoma could very efficiently perform the OPA test during a standard eye exam, according to the researchers, who added that this type of tonometer is not widely used in the United States, although it is in Europe.

The researchers say that other than CAS, very few diseases could cause low OPA scores and that an ophthalmologist could easily rule out these other diseases during an eye exam.

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