What is a Scotoma (Blind Spot in Vision)?
A scotoma is a blind spot in your field of vision. This condition may be temporary or permanent. It could stay within the same area or shift in your visual field.
Everyone has a pinhead-sized blind spot. This normal spot occurs where the optic nerve enters the retina. Most people don't notice these blind spots because our brains fill in the missing information.
On the other hand, a scotoma is an abnormal blind spot. This visual field defect might indicate an underlying health condition.
There are different kinds of scotomas:
- Central scotoma
- Scintillating scotoma
- Paracentral scotoma
Depending on the type, a scotoma might look like:
- A dark, blurry, or fuzzy spot
- A spot that flickers between light and dark
- An arc of light
- A floater
The scotoma type, as well as its duration, will depend on the underlying cause. A temporary blind spot could mean the onset of a migraine headache. Or, a more serious health issue may be contributing to vision loss.
If you notice a blind spot, call your eye doctor and schedule an appointment immediately.
Symptoms of a Scotoma
Symptoms can vary depending on the type of scotoma and its underlying cause.
Symptoms that can occur with a scotoma include:
- Vision loss (temporary or permanent)
- A blind spot (it may be one or multiple)
- Possible headache
- Floaters or dots
- Trouble reading or seeing specific colors or details
What Causes a Scotoma?
Many conditions and factors can cause a scotoma to develop, including:
A temporary scintillating scotoma might appear during the aura phase of a migraine attack. They can also occur during an ocular migraine. This type involves visual disturbances without the accompanying headache of a classic migraine.
Some drugs (e.g., digoxin) used for chronic heart failure or antiarrhythmic agents could contribute to ocular symptoms. The vision change could happen because of direct toxicity to photoreceptors.
If you develop a scotoma, discontinuing the drug can reverse this eye condition.
Sclerotherapy is a medical procedure that treats varicose and spider veins. It involves an injection into the vein to force scarring and redirect blood through other healthier veins. This can cause a scotoma.
Age-related macular degeneration (AMD or ARMD) can cause a blind spot in your central vision. AMD affects the macula, which helps with visual acuity. You can suffer from blurred vision and scotomas when it begins to deteriorate.
People with diabetes are at an increased risk for eye problems. Diabetic retinopathy occurs when high blood sugar levels damage the back of the eye (retina).
Without treatment, diabetic retinopathy can cause low vision, a central scotoma, or even blindness.
This condition happens when blood flow to the optic nerve decreases or is interrupted. This may result in sudden vision loss.
Optic atrophy is the death of retinal ganglion cells that make up the optic nerve. This condition can lead to poorer visual acuity and color vision.
Optic neuritis (swelling of the optic nerve) can cause optic atrophy. About 55% of people with Multiple Sclerosis (MS) experience optic neuritis.
A brain injury like an occipital cortex lesion rarely causes a scotoma.
Glaucoma is an eye disease that can damage the optic nerve due to fluid build-up in the front part of the eye. It can cause vision disturbances, including scotoma.
Other Health Conditions
Health conditions that are linked to scotomas include:
- Food allergies
- Preeclampsia (high blood pressure during pregnancy)
Types of Scotomas
There are three different types of scotomas:
Unlike the other types, a scintillating scotoma doesn’t look like a dark spot. A scintillating scotoma might look like:
- Flickering, pulsating, or shimmering light
- A zigzag or wave that alternates between light and dark
- An arc-shaped or jagged line
Medical professionals may refer to scintillating scotomas as teichopsia.
A central scotoma is a blind spot directly in your line of sight. This type causes visual field defects that make daily tasks seem challenging or impossible.
It can cause problems seeing colors and details. Driving and reading regular-sized print can be difficult.
People with a central scotoma may look from the side of their eyes to compensate for the defect.
Dim lighting might cause a slight improvement in central vision. Low-level lighting dilates the pupils. This lets more information about surroundings reach the retina.
A paracentral scotoma causes vision loss within 10 degrees of the focal point. This type of blind spot won’t be directly in the line of sight.
Paracentral scotomas accompanied by peripheral vision loss may cause tunnel vision.
You may have one paracentral scotoma or several depending on the underlying cause.
Who is at Risk for Scotomas?
People with the following risk factors can be more likely to develop a scotoma:
- High blood pressure
- Cardiovascular disease
- History of migraines
- High levels of stress and anxiety
- Mental health conditions, such as depression
Can a Scotoma be a Sign of Something Serious?
Yes, a scotoma can indicate an underlying health condition that requires treatment. Scotomas are more likely to develop in people who have certain health conditions. Many of these conditions, including stroke, cardiovascular disease, and MS, are serious.
It's important to consult your doctor if you develop a scotoma. They can rule out severe health problems and give you a proper diagnosis.
When to See Your Doctor
You should see your doctor if you suddenly experience a blind spot or other visual disturbances.
Seek emergency medical care if any of the following signs or symptoms accompany the scotoma:
- Confusion or disorientation
- Dizziness or nausea
- Muscle weakness
- Sudden intense headache
- Numbness in your limbs or face
- Slurred speech or difficulty speaking
A scotoma that follows a head or eye injury also warrants emergency medical care.
Are Scotomas Preventable?
People with certain health conditions are at greater risk for scotomas. You should schedule an annual eye exam to help prevent scotomas if you have:
- High blood pressure
- Cardiovascular disease
How to Diagnose a Scotoma
Your eye doctor can diagnose a scotoma with a comprehensive eye exam. They may perform various tests, including:
Visual Field Test
During this test, you will look into the opening of a bowl-shaped instrument. Each eye will be examined individually.
Small lights will flash from various areas inside the bowl. You’ll click a handheld device to indicate that you saw the flashing light.
Once you finish the test, the instrument prepares visual field maps of your eyes.
Your doctor will examine the maps and determine if you have any scotomas.
Because the instrument stores your data, you can repeat the test. This helps your doctor monitor changes in your visual field over time.
Dilated Eye Exam
Your eye doctor may use eye drops to dilate your pupils. This allows them to examine your retina and optic nerve.
They check for damage to the retina, macula, and optic nerve that may lead to a scotoma.
A dilated eye exam and visual field test can help your doctor determine the type and cause of the scotoma.
Sometimes, a doctor may refer you to a neurology clinic for a definitive diagnosis.
How to Treat a Scotoma
Scotoma treatment varies depending on the type and cause. A temporary scotoma that occurs with a migraine usually doesn’t require treatment.
Other scotomas might be alleviated by treating the underlying health condition causing it. For example, a scotoma due to high blood pressure may improve with treatments that lower your blood pressure.
Common treatments for scotomas include:
- Over-the-counter pain relievers like ibuprofen and acetaminophen
- Anti-seizure medications
- Beta-blockers to relax blood vessels
Central scotomas are not treatable with corrective lenses or surgery. However, tools and adaptive devices can help with daily activities when living with a scotoma. Examples include:
- Magnifying devices
- Large-print books
- Talking clocks and scales
- Filters to reduce glare on computer screens
- Audiobooks, magazines, and newspapers
It's critical to seek medical care and report any accompanying symptoms if you suddenly develop a scotoma. These details help your doctor determine the best approach to treatment.
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