Transient monocular blindness


Transient monocular blindness

Description, Causes and Risk Factors:

Alternative Name: Amaurosis fugax, transient monocular vision loss (TMVL).

Transient monocular blindness is loss of vision in one eye due to a temporary lack of blood flow to the retina. Transient monocular blindness is a short-lived episode of blindness in one eye (monocular). This symptom usually develops suddenly, and many individuals describe the event as “it was as if a shade or curtain came over my eye.”

It is caused by a blockage or low blood flow within the main blood vessel supplying the eye. Blockages are usually due to a blood clot or plaque (small piece of cholesterol) that breaks off from a larger artery and travels upward to the brain or eye, becoming lodged in the main artery supplying the eye. Low blood flow to the eye may also result from a critical narrowing of one of the main blood vessels supplying blood to the brain and eye.

Vision loss occurs as long as the blood supply to the artery is blocked. Atherosclerosis of the arteries in the neck is the main risk factor for this condition. Risk factors for atherosclerosis include heart disease, high cholesterol, smoking, diabetes, and high blood pressure.

Preventive Measures:

    Get screened for high blood pressure every 1 - 2 years, especially if you have a family history of high blood pressure.

  • Have your cholesterol checked. If you are high risk, your LDL "bad" cholesterol should be lower than 100 mg/dL.

  • If you have high blood pressure, diabetes, high cholesterol, and heart disease, make sure you follow your doctor's treatment recommendations.

  • Follow a low-fat diet.

  • Quit smoking.

  • Exercise regularly 30 minutes a day if you are not overweight; 60 - 90 minutes a day if you are overweight.

  • Do not drink more than 1 to 2 alcoholic drinks a day.

Symptoms:

Symptoms may include:

    Sudden loss of vision in one eye.

  • Loss of vision appearing as a gray or black shade coming down over their eye.

Diagnosis:

When interviewing a patient with transient monocular blindness, it is important to pay special attention to the medical history. The clinician should attempt to uncover the presence of hypertension, diabetes, previous myocardial infarction, prior cerebrovascular accidents, hypercholesterolemia, long standing migraine history, or peripheral vascular disease.

The eye care provider should perform biomicroscopy paying special attention to the lid margins, tear film, cornea, and anterior chamber. Conditions such as dry eyes, blepharitis, and iritis can all be ruled out from the differential diagnosis if the biomicroscopy is normal. Gonioscopy permits direct observation of the anterior chamber angle of the eye under high magnification. This clinician observation can rule out micro hemorrhage in the anterior chamber or evidence of angle closure glaucoma. Therefore, it should be performed for patient experiencing transient visual disturbance.

A dilated retinal examination is mandatory for patients presenting with transient monocular blindness. The retina, retinal vasculature, optic nerve and vitreous will all provide additional information forming a clinical diagnosis. A vitreous detachment, retinal tear, or retinal detachment should be observable once the patient's eyes are dilated.

Other tests may include an ultrasound of the carotid arteries in the neck, a study of the electrical system of the heart, a magnetic resonance angiography (MRA) scan of the blood vessels in the head and neck, an echocardiogram of the heart, or an angiogram (dye imaging of the blood vessels). If these studies reveal the source of the problem, medication and/or surgery may be necessary.

Treatment:

The treatment of transient monocular blindness depends upon identifying the source of the blood clots or cholesterol that have caused low blood flow or blocked the main artery to the eye. Blood clots may come from arteries inside the head, arteries in the neck, or from the heart. If there is evidence of blockage of more than 70% of the carotid artery, the patient may be considered for surgery to remove the blockage.

Surgery options include: Balloon angioplasty, stenting.

Both techniques are used to open up the area of the carotid artery that is blocked by plaque. These methods are promising, especially for patients who are not well enough to undergo major surgery.

The decision to perform surgery will also be based on the severity and the patient's general health. If the patient does not need surgery, doctors usually give aspirin or blood thinners.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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