Scotoma

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What is a Scotoma (Blind Spot in Vision)?

When you have a scotoma, it means you are experiencing a blind spot in your field of vision. This condition may be temporary or permanent. It could also stay within the same area or shift elsewhere in your vision. 

There are different kinds of scotomas. For example, you could have a central scotoma that is directly in your line of sight. You could also have a scintillating or paracentral scotoma.

Types of Scotomas

When you have a scotoma, it means you are experiencing a blind spot in your field of vision. This condition may be temporary or permanent. It could also stay within the same area or shift elsewhere in your vision.

There are different kinds of scotomas. For example, you could have a central scotoma that is directly in your line of sight. You could also have a scintillating or paracentral scotoma.

The scotoma type, as well as its duration, will depend on the underlying cause. 

For this reason, it is important to consult a healthcare professional or visit an ophthalmology clinic when you notice a blind spot. While a temporary blind spot could mean the onset of a migraine headache, there may be a more serious health issue contributing to the vision loss.  

Types of Scotomas

There are three different types of scotomas, including:

1. Scintillating Scotomas   

When you have a scintillating scotoma, you may experience blurred vision and have the sensation of a luminous appearance (zigzag, arc-shaped form, flickering, or shimmering) in front of your eyes. You can also consider it as an aura that obstructs your vision. It will not be a dark spot like in other forms of scotomas. 

Medical professionals may refer to scintillating scotomas as teichopsia. 

2. Central Scotomas    

A central scotoma is a blind spot that sits directly in your line of sight. When you have a central scotoma, you experience visual field defects that make specific tasks either challenging or impossible.

For example, with a central scotoma, you could have difficulty making out colors and details or even driving. You may also not be able to read regular size print well.

People with a central scotoma may look from the side of their eyes to compensate for the defect. However, in dim lighting, these individuals could notice a slight improvement in central vision. Low-level lighting dilates the pupils, letting more information about surroundings reach the retina and, ultimately, the brain.  

3. Paracentral Scotomas 

If you have a paracentral scotoma, it means you are experiencing a relative or total vision loss within 10 degrees of fixation. A paracentral scotoma will not 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 multiple paracentral scotomas. This will depend on a case-by-case basis and the underlying cause. 

What Causes a Scotoma?

Different factors or health conditions can lead to a scotoma. Let’s take a look at the various common causes per the type of scotoma. 

If you have a scintillating scotoma, it could be a result of the following:

  • Certain medications. Some drugs (e.g., digoxin) used for chronic heart failure or that act as antiarrhythmic agents could contribute to ocular symptoms. The vision change could happen because of direct toxicity to photoreceptors (cells that convert light into signals for the brain). If you develop a scintillating scotoma because of this type of drug, treatment discontinuation can reverse the eye condition. 
  • Sclerotherapy. This medical procedure helps to treat varicose and spider veins. Healthcare professionals who perform sclerotherapy will inject a solution into the vein to force scarring and redirect blood through other healthier veins. However, scintillating scotoma could appear because of possible ischemia (restriction of blood supply to tissues) of the calcarine cortex (primary visual cortex in the brain). 
  • Metastatic cancer. The American Academy of Optometry published an article where a young, 38-year-old woman experienced a scintillating scotoma. Gastrointestinal cancers metastasize to the eye in approximately 2% of women. 

If you have a central scotoma, it could be a result of the following:

  • Macular degeneration. Otherwise referred to as age-related macular degeneration (AMD or ARMD), this eye disease occurs gradually and affects the macula. The macula helps with visual acuity. When it begins to deteriorate, you can suffer from blurred vision. 
  • Diabetic retinopathy or diabetic macular edema. People with diabetes have an increased risk of having eye problems. In this case, diabetic retinopathy occurs when blood sugar levels are high and the back of the eye (retina) suffers damage. When left untreated, diabetic retinopathy can cause low vision, a central scotoma, or even blindness. 
  • Optic neuropathy. This condition happens when blood flow to the eye’s optic nerve decreases or is interrupted, resulting in sudden vision loss. 
  • Optic atrophy. This condition can cause the death of retinal ganglion cells that make up the optic nerve and lead to poorer visual acuity and color vision. Glaucoma or optic neuritis (swelling of the optic nerve) due to multiple sclerosis may be the underlying disease that results in optic atrophy. 

On rare occasions, a brain injury like an occipital cortex lesion could cause the appearance of a central scotoma. 

If you have a paracentral scotoma, it could be a result of the following:

  • Glaucoma. This eye disorder, when left untreated, can damage the optic nerve due to fluid build-up in the front part of the eye. A paracentral scotoma or an arcuate (arc-shaped) scotoma may then appear. 
  • Diabetic retinopathy. Because there is an increased risk of this eye condition for people with diabetes, an annual eye exam is recommended to ensure healthy vision and prevent severe cases. 

Symptoms of a Scotoma

Depending on the type of scotoma and its underlying cause, symptoms can vary. However, in most cases, if you have a scotoma, you will experience:

  • 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

Who is Prone to Scotomas?

People with the following risk factors can be more likely to develop a scotoma, including:

  • Diabetes
  • Glaucoma
  • High blood pressure
  • Cardiovascular disease 
  • Stroke
  • Multiple Sclerosis
  • History of migraines 
  • High levels of stress and anxiety

For example, individuals with age-related macular degeneration can develop a scotoma because the macula (area in the eye with a high concentration of photoreceptor cells) has suffered damage. While this condition may not cause complete blindness, different treatments are available to prevent a decrease in vision. 

Can a Scotoma be a Sign of Something Serious?

Yes, a scotoma could mean that you have an underlying health condition causing the issue. 

For example, a scotoma is more likely to occur in people who experience a stroke or have cardiovascular disease or multiple sclerosis. 

All of these conditions are dangerous and have negative consequences. A stroke, if left untreated, could result in brain damage, paralysis and even death. Similarly, cardiovascular disease may lead to a heart attack or other heart issues. 

For this reason, it is important to consult a doctor if you develop a scotoma and notice other symptoms. Your specialist will be able to rule out any severe health problems and give you a proper diagnosis. 

Glaucoma is the leading cause of blindness and can occur in any individual. 

When to See Your Doctor

You should visit your eye care specialist when you suddenly experience a scotoma or other visual disturbances. 

You may require emergency medical care if any of the following signs or symptoms accompany the scotoma:

  • Confusion or disorientation
  • Dizziness or nausea
  • Muscle weakness
  • Sudden extreme headache
  • Numbness in your limbs or face
  • Slurred speech or difficulty speaking
  • Scotomas after a head or eye injury

Also, certain people with health conditions have an increased risk of scotomas. For example, those with diabetes, glaucoma, high blood pressure, cardiovascular disease, or stroke should schedule an annual eye exam to prevent scotomas and receive treatment, if necessary. 

How to Diagnose a Scotoma

Visual Field Test

Your eye care specialist or trained assistant may perform an automated visual field test, otherwise known as a Humphrey visual field test. 

During this text, you will look into the opening of a bowl-shaped instrument, and each eye will be examined individually. 

While you stare at a target directly in your line of sight, small lights will flash (one at a time) 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 will prepare visual field maps of your eyes. Your eye care specialist will then examine the maps and determine if you have any scotomas. 

Because the instrument will store your data, you will be able to repeat the test. This will help the eye doctor stay on the lookout for any possible changes in your visual field over time.

Dilated Eye Exam

Apart from the automated visual field test, your eye care specialist may use eye drops to dilate the pupils of your eyes. This allows them to examine and obtain high-resolution images of the retina and optic nerve. 

As mentioned earlier, scotomas can appear due to damage caused to the retina, optic nerve, or macula. 

A dilated eye exam and visual field test will help the specialist determine the scotoma type and the underlying cause. When it’s not possible, you may receive a referral to a neurology or neuro-ophthalmology clinic for a definitive diagnosis. 

How to Treat a Scotoma

Treatment for a scotoma will depend on the cause. It is important to seek medical help and report any accompanying symptoms with a sudden scotoma. Your medical history and these details will help your healthcare professional decide the next step in treatment.

Resources
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Klemens , Adam. INVASIVE ADENOCARCINOMA PRESENTING AS A SCINTILLATING SCOTOMA, 2021, www.aaopt.org/detail/knowledge-base-article/invasive-adenocarcinoma-presenting-scintillating-scotoma.

Mittra, Robert A, and William F Mieler. “Drug Toxicity of the Posterior Segment.” Retina (Fifth Edition), W.B. Saunders, 28 Nov. 2012, www.sciencedirect.com/science/article/pii/B9781455707379000898.

Nezemi et al. , Paul. “Scotomas of Age-Related Macular Degeneration Detected and Characterized by Means of a Novel Three-Dimensional Computer-Automated Visual Field Test.” Retina (Philadelphia, Pa.), U.S. National Library of Medicine, 2005, pubmed.ncbi.nlm.nih.gov/15933591/.

“Paracentral Scotoma Nerve Loss.” American Academy of Ophthalmology, 25 Sept. 2014, www.aao.org/image/paracentral-scotoma-nerve-loss-2.

Partsch, Hugo. “Complications and Adverse Sequelae of Sclerotherapy.” Edited by John Bergan et al., Sclerotherapy (Fourth Edition): Treatment of Varicose and Telangiectatic Leg Veins, 22 June 2020, www.sciencedirect.com/science/article/pii/B9780323042581500135.

“Scotomas.” Scotomas - Causes of Vision Loss (CA School for the Blind), www.csb-cde.ca.gov/resources/causesvl/cvl-scotomas.aspx.

“Table: Types of Field Defects.” Merck Manuals Professional Edition, www.merckmanuals.com/professional/multimedia/table/v1152087.

“Vision, Blind Spot (Scotoma).” Tufts Medical Center Community Care, hhma.org/healthadvisor/aha-scotoma-oph/.

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