Flashes & Floaters

Flashes & Floaters

Flashes & Floaters Introduction

One of the most common problems that patients experience when visiting a retinal specialist is seeing flashes of light or floaters in one or both eyes. These visual disturbances, known as photopsias, are caused by events inside the eye or elsewhere in the visual system. Understanding the anatomy of the eye and brain, as well as how vision works, helps explain why these occur.

Anatomy and Physiology

The eye is a spherical organ that enables us to see. The cornea allows light to enter the eye, and the lens focuses it on the retina, which acts like the film in an old camera or the sensor in a digital one. The center of the eye is filled with a clear, gel-like substance called vitreous. In youth, the vitreous is perfectly clear with a consistency similar to gelatin. Over time, it liquefies and develops fluid pockets, condensations, and opacities.

Vision begins when light is focused on the retina, which converts the images into electrical impulses. These signals travel along the optic nerve to the brain. At the optic chiasm, half of the visual information from each eye crosses to the opposite side of the brain. This means the right side of the world is processed by the left brain and vice versa. This distinction helps doctors determine whether symptoms originate in one eye or the brain.

Floaters

Floaters appear as dark spots moving through your field of vision. They are more noticeable in bright light or when looking at plain backgrounds, such as a blue sky or white wall. As we age, the vitreous gel liquefies, and floaters become more common. When the vitreous detaches from the retina, patients may experience a sudden increase in floaters, often accompanied by flashes of light.

Floaters can also result from other eye conditions such as diabetic retinopathy, asteroid hyalosis (calcium deposits in the vitreous), or inflammation (uveitis). Rare causes include amyloidosis and lymphoma. In these cases, further evaluation or biopsy may be necessary.

Flashing Lights

Flashing lights are typically caused by traction on the retina due to vitreous separation. These flashes are brief, peripheral, and most visible in the dark. They often occur when moving suddenly or waking up at night. Retinal detachment can also cause a persistent or glowing light in the periphery. Another cause of flashing lights is migraine aura, which produces shimmering or zigzag patterns that last up to 30 minutes and occur in both eyes.

Vitreous Separation

The sudden onset of flashes and floaters often indicates vitreous detachment. As the vitreous ages, it liquefies and separates from the retina, which can sometimes cause retinal tears or bleeding. Blood in the vitreous appears as dark floaters. Retinal tears must be treated promptly to prevent retinal detachment. Surgery is rarely needed unless floaters or bleeding are severe.

Migraine Phenomena, Aura and Headaches

Migraines can also cause flashing lights, known as aura. These lights form jagged or saw-tooth patterns, often lasting 15–30 minutes, and may be followed by headaches. Migraine auras occur in both eyes and are linked to abnormal brain activity. Some individuals experience the aura without the headache. Migraines can be triggered by hormonal changes, stress, or environmental factors and may run in families. Those with frequent or severe migraines should consult a neurologist.

Retinal Tears and Holes

Acute retinal tears require immediate attention. Treatment aims to seal the tear with laser or cryopexy (freezing therapy) to prevent fluid from detaching the retina. Both methods are highly effective, with about a 95% success rate. Retinal holes without symptoms may not need treatment, depending on their type and risk factors.

Lattice Degeneration

Lattice degeneration is a common retinal condition affecting about 7% of the population. It increases the risk of retinal tears and detachment but usually does not affect vision directly. The risk of detachment rises slightly in people with this condition. Treatment is considered in cases with a strong family history, detachment in one eye, or extensive lattice degeneration, especially for those living far from medical care.