Different Strokes

It’s estimated that around two in 100,000 people in the US will suffer from central retinal artery occlusion (CRAO) each year, with this incidence rising to around 10 per 100,000 in those aged over 80 (1). These acute ischemic strokes occur suddenly, leading to retinal hypoperfusion and rapidly progressive cellular damage that can cause permanent retinal damage in just over 90 minutes (2). To improve patient outcomes and prevent permanent vision loss, swift diagnosis and accurate treatment is crucial – and that’s why CRAO is categorized as an ocular emergency by the American Academy of Ophthalmology (AAO).

In an effort to accelerate the turnaround times for CRAO patients, a New York-based team of researchers have developed an innovative protocol for the emergency departments and stroke centers within the Mount Sinai health system (3). The researchers placed semi-automated optical coherence tomography (OCT) machines at three hospitals in the catchment area to image adults presenting with painless monocular vision loss; these OCT images were then interpreted remotely by the team’s retina service, precluding the need for an in-house ophthalmology consult.

“The remote teams of retinal surgeons, stroke neurologists, [and] interventional radiologists review the OCT images and clinical data from residents onsite, and confirm or reject the diagnosis of retinal ischemia versus retinal detachment, vein occlusion, vitreous hemorrhage, or wet macular degeneration,” explains Richard B. Rosen, Chief of the Retina Service for the Mount Sinai Health System. “Their agreed evaluation drives the decision of the interventional radiologist to proceed or not.”

OCT has been shown to detect retinal edema more “easily and rapidly in the acute setting” than fluorescein angiography (1), and the swift remote diagnosis it enables in the new protocol allows for more timely administration of intra-arterial tissue plasminogen activator (IA-tPA) in the patient. tPA, a protein used for breaking down blood clots, has been shown to provide a statistically significant “improvement in visual acuity of three lines or more” when administered early on in the onset of CRAO (4).

The most compelling finding in their Ophthalmology study, says Bosen, was “the successful return of vision in patients after up to 12 hours from the time of the onset of CRAO.” He adds that the positive impact of IA-tPA is something that some previous studies, such as the EAGLE trial, have failed to highlight for CRAO patients.

Given that the study results showed “clinically significant improvement [...] in 66 percent of patients within 24 hours” (3), the expansion of OCT availability in emergency rooms and stroke units throughout the country could reduce the vision loss statistics associated with CRAO. But along with faster diagnostics must come increased public awareness of eye strokes, says Rosen. “This is the critical effort. Most patients present too late to be treated. Better public awareness would save vision in more people. We have spent time educating our medical colleagues as to the availability of the treatment and the time sensitivity, but a large-scale public educational effort is needed, as was done many years ago for cerebral stroke.”