“Ocular pulse amplitude” test, can reliably detect carotid artery stenosis, a condition that clogs or blocks the arteries feeding the front part of the brain and is also known as the risk factor for strokes

A research study at the University of Zurich has found that a simple eye test which could be used to identify people who are at high risk for a stroke. According to the researchers, the test called "ocular pulse amplitude" (OPA), can reliably detect carotid artery stenosis (CAS), a condition that clogs or blocks the arteries feeding the front part of the brain and is also known as the risk factor for strokes.  

Lead researcher Pascal Bruno Knecht, MD said, "Our results show that ocular pulse amplitude is a reliable, safe screening test for carotid artery stenosis. 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, physicians who treat eye diseases during routine exam, can perform the OPA test, a press release from American Academy of Ophthalmology (AAO) said. It added that every year about 7.9 lakh Americans suffer a new or recurrent stroke, as result more than 1.3 lakh of these people die. "People with severe CAS are much more likely to suffer a stroke. Physicians would like to catch and treat CAS before that can happen, but because CAS has no symptoms and as an efficient test is not currently available, the disease often goes undetected."

Explaining the study, AAO said that the Swiss research team, using a device named the dynamic contour tonometer, checked the OPA of 67 patients assumed to have CAS. The OPA score is calculated based on the difference between the two pressure levels that occur inside the eye during the two phases of the heartbeat-the systolic and diastolic. The tonometer measures the two pressure levels, then instantly computes the patient's OPA score. When blood flow to the eye is blocked by CAS, there is not much difference between the two pressure levels, so the OPA score is low.

According to the study, patients with the lowest OPA scores also had the most seriously blocked arteries. The researchers used ultrasound exams to corroborate that each study participant had CAS and to detail the severity of his or her blockage.

The findings were also validated by Ophthalmology, the journal of the American Academy of Ophthalmology in it June issue, stating that patients with the lowest OPA scores also had the most seriously blocked arteries.

According to the research review by the US Preventive Services Task Force, the incidence of stroke and fatalities from it could be substantially reduced if efficient screening test for CAS were available. It noted that test should be able to detect clinically significant CAS, defined as 60%-99 % blockage of the carotid arteries. "Some high-tech tests, such as magnetic resonance angiography and colour duplex ultrasound, already meet this standard, but they are expensive and not widely available. Their primary use is in diagnosing patients who already have symptoms of stroke."

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."