A retinal microembolism is a small piece of debris or a clot which travels through your bloodstream and then becomes lodged inside a small blood vessel in your retina and obstructs blood flow.
The emboli can be made of cholesterol, platelet fibrin, calcium and other substances.
Retinal emboli or retinal microembolism often originates from sources like your carotid arteries, "heart" in cases of atrial fibrillation or vascular disease, or aortic arch.
When a microembolism does block a retinal artery it can then cause a sudden and painless and even potentially severe loss of vision in the eye that is affected and is known as retinal artery occlusion.
There are different types of retinal emboli or retinal microembolism which include platelet fibrin emboli, calcium emboli and cholesterol emboli.
Although retinal artery occlusion can sometimes lead to and cause significant vision loss, some people may only experience transient vision disturbances or have no symptoms of retinal microembolism at all.
That is if the microembolism is small or only briefly blocks the artery.
Having retinal microembolism even if you have no symptoms can be a good indicator of underlying cardiovascular disease and require further investigation like a carotid ultrasound or other vascular imaging to assess your risk of any future stroke or cardiovascular events.
Retinal microembolism can be detected most often during a routine eye exam or by observing your retinal arteries through a dilated pupil.
Retinal microembolism is a warning sign which can indicate that you have a broader issue with your circulatory system and so it's important to seek medical attention if you experience any sudden changes in your vision or if the retinal emboli is detected during an eye exam as it can be a sign of a more serious underlying medical conditions.