A “blood clot in the eye” commonly describes Retinal Vascular Occlusion, a serious medical condition. This occurs when a blockage forms in one of the blood vessels serving the retina, the light-sensitive tissue at the back of the eye. The two main forms are Retinal Artery Occlusion (RAO) and Retinal Vein Occlusion (RVO), which block the flow of blood into or out of the eye. Both types deprive the retina of necessary oxygen and nutrients, posing a significant threat to vision. Because the retina’s delicate nerve cells can suffer irreversible damage within hours, this condition is treated as a time-sensitive medical emergency.
Recognizing the Signs of an Ocular Clot
The symptoms depend on whether the blockage is in an artery or a vein. Retinal Artery Occlusion (RAO) often presents as a sudden, nearly complete, and usually painless loss of vision in one eye. This rapid visual change often leads to it being described as an “eye stroke.”
In contrast, Retinal Vein Occlusion (RVO) causes more variable symptoms, ranging from a sudden decrease in clarity to a gradual blurring that worsens over hours or days. Patients might also notice a sudden increase in floaters, which appear as dark spots drifting across their field of view. These floaters are caused by blood or fluid leaking from the blocked vein. The severity of vision loss depends on whether the central main vessel or a smaller branch vessel is affected.
Emergency Protocol and Medical Evaluation
The immediate action upon noticing any sudden change in vision is to seek emergency medical care, such as calling 911 or visiting the nearest emergency department. Prompt action is necessary, particularly with suspected Retinal Artery Occlusion, where the window for effective treatment is narrow. The goal is to restore blood flow to the retina before permanent cell death occurs, which can begin in as little as 90 minutes.
Once in the emergency setting, a team including an ophthalmologist will perform an evaluation. The initial assessment involves a complete eye exam, visual acuity testing, and a funduscopic examination to view the back of the eye. Specialized imaging tests are then used to confirm the diagnosis and pinpoint the location of the occlusion.
Optical Coherence Tomography (OCT) provides high-resolution images to detect swelling (macular edema) caused by fluid leakage. Fluorescein angiography (FA) is also often performed, involving injecting a dye into the bloodstream and taking rapid photographs of the retina. This test reveals the specific location and extent of the blockage, helping to differentiate the type of occlusion and guiding the treatment plan.
Treatment Strategies for Ocular Occlusions
Treatment strategies depend on the specific vessel blocked. Retinal Artery Occlusion (RAO) requires immediate intervention to attempt to dislodge the clot. For RAO, techniques like ocular massage are sometimes attempted, where firm pressure is applied and released on the closed eyelid. This aims to help move the clot into a smaller vessel where it may cause less damage.
Another procedure is anterior chamber paracentesis, where a tiny amount of fluid is removed from the front of the eye to rapidly lower intraocular pressure. Lowering the pressure can theoretically help propel the clot forward. In specialized stroke centers, intravenous delivery of clot-dissolving tissue plasminogen activator (tPA) may be considered. This must be administered within a few hours of symptom onset and carries risks. If vision loss is not reversed quickly, the prognosis for regaining full sight is often poor.
Treatment for Retinal Vein Occlusion (RVO) focuses on managing the main complication: macular edema, which is swelling of the central retina caused by fluid leakage. The standard approach involves intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents, such as ranibizumab or aflibercept. These medications are administered directly into the eye and work by neutralizing a protein that causes vessels to leak fluid and promotes abnormal vessel growth.
Anti-VEGF injections are effective in reducing macular swelling, often leading to visual improvement. An alternative approach involves corticosteroid implants, such as dexamethasone, which are also injected into the eye. Steroids reduce inflammation and leakage. If the vein occlusion causes fragile, abnormal new blood vessels (neovascularization), laser photocoagulation may be used to destroy these vessels and prevent further bleeding and pressure problems.
Addressing Systemic Risk Factors
An ocular vascular occlusion is often a sign of underlying systemic health conditions that affect blood flow throughout the body. The risk factors for a retinal clot are similar to those for a heart attack or a stroke. Conditions such as uncontrolled high blood pressure (hypertension), elevated cholesterol levels (hyperlipidemia), and diabetes are major contributors.
These conditions damage the inner lining of blood vessels, leading to the formation of plaques and clots that can travel to the eye. For instance, in RAO, the clot often originates from plaque buildup in the carotid arteries or from an irregular heart rhythm like atrial fibrillation. After the acute eye emergency is managed, a systemic evaluation is necessary to identify and manage these underlying issues.
This evaluation often includes imaging of the carotid arteries and heart monitoring. Long-term management requires collaboration with a primary care physician to control blood pressure, blood sugar, and cholesterol levels. Managing these systemic factors is the most effective way to lower the risk of recurrence and protect against future stroke or heart attack.