When people report seeing circular, translucent, or floating shapes, often referred to as “orbs,” the experience can be unsettling. These sightings, whether perceived directly or captured through a camera lens, have scientific and physiological explanations. This article explores the mechanisms behind these phenomena, focusing on origins within the eye, activity in the brain, and external environmental factors. Understanding these physical causes can demystify the experience and provide clarity on what is being observed.
Ocular Explanations: Debris in the Vitreous Humor
The most frequent physiological cause for seeing floating shapes is the presence of muscae volitantes, commonly known as eye floaters. These shapes originate within the vitreous humor, the clear, gel-like substance filling the space between the lens and the retina. The vitreous humor is composed mainly of water and a meshwork of collagen fibers.
As a person ages, the vitreous gel naturally begins to liquefy and shrink, a process called syneresis. This causes the collagen fibers to clump together, forming microscopic debris or strands. When light enters the eye, these clumps cast shadows onto the retina. The brain perceives these shadows as floating specks, webs, or translucent circles that drift when the eye moves.
This age-related change often results in a Posterior Vitreous Detachment (PVD), where the vitreous body separates from the retina. PVD is common, especially after age 50, and can introduce a sudden, large floater or a ring-like shape into the vision. Because floaters are suspended within the gel, they lag behind the eye’s movement, which distinguishes them from external objects.
Neurological Explanations: Visual Cortex Activity
Some visual phenomena resembling orbs or shimmering spots originate from the visual cortex, the brain’s visual processing center, rather than the eye’s structure. These neurological events involve electrical or chemical activity generating a visual perception without external light stimulus. The primary example of this is the visual disturbance known as a migraine aura.
A migraine aura often appears as a shimmering, expanding pattern, such as a zigzag line or an arc of light, known as a scintillating scotoma. The initial point of a developing aura can be a small, bright spot that expands across the visual field. This phenomenon is binocular, affecting both eyes simultaneously, which differentiates it from a localized eye issue.
Another neurological cause is the generation of phosphenes, which are brief flashes or sparks of light. Phosphenes can be triggered by mechanical stimulation of the retina, such as rubbing the eyes, or occur spontaneously due to internal electrical activity. These momentary perceptions of light are processed by the visual cortex, giving the illusion of a sudden light source or an internal orb.
Environmental and Photographic Artifacts
Many instances of reported orbs occur in photographs, especially those taken in low-light conditions with a flash. These photographic orbs are not biological phenomena but optical artifacts known as backscatter. Backscatter occurs when the camera’s built-in flash illuminates small airborne particles located very close to the lens.
These particles are typically dust motes, pollen, or moisture droplets suspended in the air. Since the particles are close to the camera, they are far outside the lens’s focal plane and appear highly blurred. The light reflecting off these out-of-focus particles is diffused, creating the characteristic translucent, circular shape, an effect that photographers refer to as bokeh.
The close proximity of the flash unit to the lens on most compact and smartphone cameras exacerbates this issue, brightly illuminating the particles. External visual anomalies, such as lens flare, can also create circular shapes. Lens flare occurs when non-image-forming light strikes the lens and scatters, creating internal reflections that appear as circles or polygons across the image.
Knowing When to Seek Medical Attention
While most floaters and light flashes are benign consequences of aging, certain symptoms indicate a serious eye condition requiring immediate medical consultation. A sudden and dramatic increase in the number of floaters, especially if they appear all at once, is a warning sign. This change can be associated with a retinal tear or detachment.
The perception of flashes of light, medically termed photopsia, also warrants urgency, particularly if it accompanies new floaters. These flashes suggest the vitreous gel is pulling on the retina, stimulating the light-sensitive tissue. A serious sign is a dark shadow or a curtain-like veil that moves across the field of vision or blocks peripheral sight.
These symptoms—a sudden flood of new floaters, accompanying light flashes, or a visual curtain—can signal a sight-threatening condition like a retinal detachment. Prompt evaluation by an eye care professional is necessary to prevent permanent vision loss.