What causes eye floaters

Overview

Eye floaters are the small spots, specks, or wisps that drift across your field of vision. They are particularly noticeable when you look at a plain, bright background, such as a blue sky or a white wall. While they can be annoying, most eye floaters are a harmless part of the aging process and do not require treatment. However, in some cases, they can be a sign of a more serious underlying eye condition.

What Are Eye Floaters?

Your eyes are filled with a clear, jelly-like substance called the vitreous humor, or simply the vitreous. This gel occupies the space between the lens and the retina at the back of your eye. The vitreous is crucial for maintaining the eye's shape and allowing light to pass through to the retina, where images are formed.

Over time, the vitreous gel naturally undergoes changes. It can start to liquefy, becoming more watery, and shrink. As it shrinks, it can develop small clumps or strands. These clumps are technically called 'muscae volitantes' (Latin for 'flying flies') but are commonly referred to as floaters. These clumps cast tiny shadows on the retina, and it's these shadows that you perceive as floaters moving around in your vision.

Common Causes of Eye Floaters

1. Age-Related Vitreous Changes (Vitreous Syneresis)

This is by far the most common cause of eye floaters, particularly for people over the age of 50. As the vitreous liquefies and shrinks, it can pull away from the retina. This process is known as Posterior Vitreous Detachment (PVD).

PVD is a natural aging process. The vitreous gel is attached to the retina at various points. As it shrinks, these attachments can break. Often, the vitreous detaches completely from the retina. Sometimes, small bits of the vitreous or retinal tissue can break off and float in the liquefied vitreous, becoming visible as floaters. You might also experience flashes of light (photopsia) during PVD, as the shrinking vitreous tugs on the retina.

2. Posterior Vitreous Detachment (PVD)

As mentioned above, PVD is a specific type of age-related change where the vitreous separates from the retina. While it's a normal part of aging, it can sometimes lead to complications. The sudden appearance of numerous floaters, especially accompanied by flashes of light, is a hallmark symptom of PVD. Most of the time, PVD is benign, and the floaters gradually become less noticeable as your brain learns to ignore them or they settle lower in the vitreous cavity.

3. Posterior Uveitis (Inflammation Inside the Eye)

Inflammation in the middle layer of the eye (uvea), particularly the part at the back, can cause floaters. This condition, known as posterior uveitis, can be triggered by infections (like toxoplasmosis, syphilis, or CMV), autoimmune diseases (like sarcoidosis or Behcet's disease), or sometimes have no identifiable cause. Inflammatory cells and debris can be released into the vitreous, appearing as floaters. Uveitis often causes other symptoms like blurred vision, pain, and light sensitivity, in addition to floaters.

4. Vitreous Hemorrhage (Bleeding in the Vitreous)

Bleeding into the vitreous gel can also create floaters. This can occur due to several reasons:

• Diabetic Retinopathy: In people with diabetes, high blood sugar levels can damage the blood vessels in the retina, causing them to leak or rupture and bleed into the vitreous.
• Retinal Tears or Detachment: As the vitreous pulls away from the retina (PVD), it can sometimes tear the retina. A tear can lead to bleeding.
• Trauma: A direct injury to the eye can cause blood vessels to break and bleed into the vitreous.
• Blockage of Blood Vessels: A blockage in a retinal blood vessel can cause blood to leak into the vitreous.

Floaters caused by bleeding often appear as a sudden shower of small dots or a hazy cloud, and they may be accompanied by a sudden decrease in vision.

5. Other Less Common Causes

• Retinal Tears: While PVD often causes floaters, it can sometimes lead to a retinal tear. If the vitreous pulls strongly enough on a weak spot in the retina, it can create a tear. This is a serious condition that requires immediate medical attention to prevent vision loss. A sudden increase in floaters, especially accompanied by flashes of light or a curtain-like shadow in your vision, can be a sign of a retinal tear or detachment.
• Myopia (Nearsightedness): People who are highly nearsighted are more prone to developing floaters earlier in life, as their eyeballs are typically longer, leading to earlier vitreous changes.
• Eye Surgery or Injections: Procedures like cataract surgery or injections into the eye (e.g., for macular degeneration) can sometimes introduce small air bubbles or cause minor bleeding, which may appear as floaters.
• Eye Tumors: Although very rare, tumors within the eye can sometimes cause floaters.

When to See a Doctor

While most floaters are harmless, it's crucial to seek prompt medical attention from an eye doctor (ophthalmologist or optometrist) if you experience any of the following:

• A sudden increase in the number of floaters.
• The appearance of new, small floaters accompanied by flashes of light.
• A shadow or curtain-like darkness appearing in part of your vision.
• A sudden decrease in vision.
• Eye pain along with floaters.

These symptoms could indicate a retinal tear or detachment, which is a medical emergency that requires immediate treatment to preserve vision.

Diagnosis and Treatment

An eye doctor will perform a comprehensive eye exam, including dilating your pupils to get a clear view of the retina and vitreous. If the floaters are due to age-related changes and are not causing significant vision impairment, no treatment is usually necessary. Your brain will often learn to ignore them over time. However, if floaters are caused by an underlying condition like uveitis or a retinal tear, prompt treatment is essential. Treatments vary depending on the cause and can include medications for inflammation, laser surgery, or vitrectomy (surgical removal of the vitreous) in severe, persistent cases.