What Causes Flashing Crescent Shapes and Circles in Vision?

Why Am I Seeing a Bright White Circle in My Vision?

Occasionally seeing a bright white circle or arc in your field of vision can be alarming. However, in many cases these visual disturbances are harmless. Understanding the common causes can help determine if further evaluation is needed.

Floaters as a Cause

One of the most common reasons people see a bright crescent shape is due to floaters in the eyes. Floaters are tiny clumps of protein or collagen fibers that form in the vitreous humor, the gel-like fluid inside the eye.

As we age, the vitreous starts to break down and condense, forming stringy floaters. These can cast shadows on the retina, appearing as small dots, circles, strands or cobwebs in vision.

A semicircular or C-shaped floater may move and change shape. While annoying, regular floaters are usually not a major concern.

When Floaters May Indicate a Problem

See an ophthalmologist promptly if floaters appear suddenly and are:

• Numerous and dense
• Accompanied by light flashes
• Associated with vision loss

This could signify a torn or detached retina, which requires urgent treatment.

Posterior Vitreous Detachment

As the vitreous humor ages, it can pull away from the retina in clumps, causing posterior vitreous detachment (PVD). This can make you temporarily see:

• Small, circular blobs
• Flashing arc or crescent shapes
• Lightning bolt-like zigzags

PVD may also cause brief vision blurriness. Symptoms typically resolve within a few weeks or months as the vitreous separates completely.

Retinal Migraines

Seeing an arc or C-shaped flash of light can also stem from retinal migraines. These headaches involve blood vessel spasms in the retina instead of the brain.

Classic symptoms of a retinal migraine include:

• Temporary blindness or vision loss in one eye
• Seeing flashing or shimmering arcs, spots or zigzags
• Visual disturbances lasting 5 to 20 minutes
• Mild headache after the visual symptoms

Retinal migraines are harmless for most people. But recurrent ones may warrant further evaluation for eye or blood vessel issues.

Vitamin Deficiencies

Lack of certain vitamins can affect the eyes and visual pathways in the brain, causing abnormal visions like light flashes.

Deficiencies associated with semicircular flashes or floaters include:

• Vitamin A
• Vitamin E
• Vitamin B complex
• Folate

Taking supplements may improve symptoms if a vitamin deficiency is identified. But always consult your doctor first.

Eye Inflammation

Inflammation inside the eye, known as uveitis, can sometimes produce crescent-shaped lines or flashes in vision. Possible causes of uveitis include:

• Autoimmune disorders
• Infections
• Injury to the eye
• Surgery complications

Uveitis requires prompt treatment to prevent vision damage. See an ophthalmologist if flashing arcs accompany eye redness or pain.

Eye Muscle Spasms

Uncontrolled eye muscle movements or spasms may cause temporary visual distortions like arcs and flashes. This can result from:

• Electrolyte imbalances
• Drug or alcohol withdrawal
• Neurological disorders

If intrusive and persistent, an eye doctor can evaluate for any underlying disorder causing eye muscle instability.

Optic Nerve Inflammation

The optic nerve connects the eye to the brain. When it becomes inflamed or disturbed, called optic neuritis, visual abnormalities can occur such as:

• Brief loss of vision
• Diminished color perception
• Flashing lights or arcs
• Eye pain, especially with movement

Optic neuritis sometimes results from multiple sclerosis (MS). Prompt treatment helps prevent permanent vision loss.

Occipital Lobe Disturbances

The occipital lobes at the back of the brain process visual information. Irritation or injury to this area of the brain can cause various visual hallucinations.

Causes may include:

• Migraines
• Seizures
• Head trauma
• Tumors
• Stroke

Evaluation is recommended if new onset of flashing shapes or lights appear without other eye abnormalities.

Medication Side Effects

Certain prescription and over-the-counter medications are associated with visual disturbances like halos, flashing lights and floaters as a side effect. These include:

• Antivirals
• Antibiotics
• High blood pressure medications
• Anti-inflammatories

Talk to your doctor if new medications coincide with seeing flashing arcs or spots in vision.

When to Seek Emergency Care

Seek prompt emergency care if flashing arcs or crescents appear suddenly and are accompanied by:

• Sudden vision loss or blindness
• Eye pain or headache
• Nausea and vomiting
• Dizziness

These can signify a tear or detachment in the retina that requires urgent treatment to prevent permanent vision damage or loss.

The Bottom Line

In many cases, brief flashes of light or floaters in crescent shapes are harmless results of vitreous changes in the eyes. But sudden onset, especially with other symptoms like pain or vision loss, warrants prompt medical evaluation to rule out retinal issues or neurological causes.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.