Acute Central Retinal Artery Occlusion Stage Identifiable With OCT

In acute central retinal artery occlusion (CRAO), optical coherence tomography (OCT) can illustrate changes through various disease stages, according to research published in the International Journal of Retina and Vitreous. The study shows that OCT imaging provides an objective measure of opacification throughout retinal layers associated with thinning.

opacification of middle retinal layers and prominent middle limiting membrane (p-MLM) sign. In scans during more than 1 month of observation, OCT showed evolving structural features, all leading to inner retinal layer thinning.

Investigators reviewed records of 39 eyes of 38 patients (mean age, 49.5 years) with acute central retinal artery occlusion symptoms for less than 7 days, imaged with spectral-domain OCT scans at a retina clinic from June 2017 to November 2022. At presentation, patients were staged as being mild (n=11), moderate (n=16), or severe (n=12).

Eyes with mild disease displayed middle retinal layer opacification, connected to gradual inner layer thinning. Those with moderate acute CRAO showed overall inner layer opacification, also related to eventual retinal thinning. Prominent middle limiting membrane (p-MLM) sign was present during these 2 stages, but then diminished. In moderate and severe disease, emerging signs included inner retinal fluid-filled cavities, detachments in internal limiting membrane or neurosensory layers, and hyperreflective posterior vitreous opacities.

When acute CRAO is severe, acute inner layer cell swelling typically prompts hyperreflectivity of inner layers — potentially causing p-MLM to disappear from OCT images. “As a result, in acute CRAO, the p-MLM sign is an indicator of less severe ischemic damage and may be a factor associated with a better visual acuity out­come,” researchers report. Two previous studies reported comparable findings regarding p-MLM sign. “Based on the concept of reperfusion injury seen with acute CRAO, these signs can be explained as follows: Once the critical duration of ischemia is exceeded in acute CRAO, retinal cell injury and/or death occur,” the researchers explain.

Investigators caution that middle layer opacification can be mistaken for a sign of cilioretinal artery occlusion or paracentral acute middle maculopathy, but in these, opacification is more often temporal to the optic disc or in a paracentral macular location, respectively. Also, inner layer thinning occurs with advanced chronic glaucoma, but is more uniform and mostly impacts ganglion cell and RNFL layers.

A limitation of this analysis is image categorization based on duration of symptoms — from onset (day 0) to 7 or fewer days, 8 to 14, 15 to 30, and more than 30 days — rather than standardized intervals. This study offers pertinent data on OCT-derived characteristics to help evaluate ischemic severity, and indicators for patients’ ultimate visual results.