Intravenous thrombolysis can be an effective therapeutic option for the treatment of central artery occlusion (CRAO); However, no imaging tests have been established to assess retinal viability, explains a systematic review published in the Journal of Stroke and Cerebrovascular Diseases. Research reveals existing and experimental imaging modalities that may be useful in treating CRAO.
The retina consists of a dual circulatory anatomy in which the inner retinal vasculature is obtained from the central retinal artery and the outer retinal choroid is received from the posterior ciliary circulation. Recent evidence suggests that retinal tissue can be saved within 4.5 hours of CRAO with restoration of blood flow. The elasticity of retinal tissue may be due in part to the anatomy of dual circulation, which allows for passive diffusion of oxygen from the outer retina and choroid.
There are 3 standard imaging modalities for patients with CRAO (fluorescein angiography, fundus photography, and transorbital ultrasound). Optical coherence tomography (OCT) and functional imaging of the retina are experimental procedures with fascinating results that can improve the treatment landscape for patients with CRAO.
The standard technique used to confirm CRAO is fluorescein angiography, which can detect normal choroidal filling and circulation, as well as delays in arterial blood flow or arteriovenous transit time. Fundus photography can identify early symptoms of segmental blood flow and non-blood flow to the retinal arteries, as well as the late symptoms of retinal lightening or the cherry red spot. Transorbital ultrasound detects the “spot sign” and the decreased blood flow in the central retinal artery.
OCT is non-invasive with weakly coherent light and provides three-dimensional images of tissue at a depth of 22 mm with a resolution of 1 µm to 10 µm. The technique was mainly used to measure structural thicknesses in the retina. As part of CRAO, changes in the intestine in the retinal layers can be detected. For this imaging modality to be useful in assessing retinal viability, biomarkers of altered retinal anatomy are still required.
Functional imaging of the retina is a non-invasive procedure that enables functional and structural examination. It has a similar resolution to OCT, but with a larger field of view. This imaging modality produces 4 detailed outputs that include capillary perfusion maps, blood flow rate, retinal oxygenation, and retinal metabolism function. This instrument was used to assess blood flow in patients with retinitis pigmentosa, diabetic retinopathy, and multiple sclerosis. No studies in the CRAO setting have currently been published.
The researchers conclude that the treatment of acute stroke has been changed by multimodal imaging tools. It is hoped that analogous techniques will have a similar effect on the treatment of CRAO. There are currently no validated modalities that provide rapid and accurate data on the viability of retinal tissues. Both OCT and functional retinal imaging, with additional studies, have the potential to improve the care landscape for patients with CRAO by allowing clinicians to determine whether retinal tissue remains viable and could be viable candidates for intravenous thrombolysis .
B. Mac Grory, M. Schrag, S. Poli, et al. Structural and functional imaging of the retina with occlusion of the central retinal artery – current approaches and future directions. J Stroke Cerebrovasc Dis. 2021; 30 (7): 105828. doi: 10.1016 / j.jstrokecerebrovasdis.2021
This article originally appeared on Ophthalmology Advisor