If you look up at a bright, blue sky (without staring directly at the sun, of course!) you might catch sight of tiny dots that look like moving light dancing in your field of vision.
No, you are not hallucinating or imagining it; this can be a visual occurrence known as Blue Field Entoptic Phenomenon (BFEP), and while not usually a cause for concern, it is worth noting that the visible specks it creates can mirror eye floaters and these do need to be looked at by an optometrist.
How does Blue Field Entoptic Phenomenon work?
As German physicist and inventor of the ophthalmoscope Hermann von Helmholtz once explained, entoptic perceptions, like BFEP, occur when suitable light conditions fall on the eye and make certain objects within the eye itself visible.
When you experience BFEP, you are actually seeing your own white blood cells coursing through your eyes.
As blood flows to the eyes through vessels that travel across the retina, red blood cells absorb blue light, which white blood cells transmit to the retina. This, in turn, sends a signal of heightened brightness to the brain.
“The dots you perceive, which resemble the likes of little ants in motion, are a result of white blood cells navigating through the blood vessels in your eyes. This phenomenon becomes particularly noticeable when you fix your gaze on a wide, clear blue expanse such as a pristine blue sky,” said Dom Willson, optometrist and Professional Services Advisor at Optometry Australia.
The speed of these moving dots also synchronises with your pulse, meaning they accelerate with each heartbeat. A dark tail – which is the congregation of red blood cells trailing behind the more sluggish-moving white blood cell – accompanying the dot of light may also be observed.
Does BFEP differ from floaters or flashes?
It's crucial not to confuse the Blue Field Entoptic Phenomenon with eye issues like floaters or flashes, which can seem similar in appearance.
“Floaters, which are composed of clumps or strands in the gel-like fluid in your eye known as the vitreous. They vary in size and brightness, and drift more slowly with eye movements, settling when the eye is still. As for flashes, these tend to resemble flickering or flashing light streaks or stars which may persist intermittently for weeks or even months."
While the moving dots associated with BFEP are uniform in size and shape and continue their journey across your vision even if your eyes cease to move, floaters and flashes can sometimes be indicative of more serious eye problems.
- Posterior Vitreous Detachment (PVD) occurs when the vitreous separates from the retina. This separation can cause floaters and flashes of light. While PVD is a common part of aging and is usually not harmful, it's essential to have any sudden onset of symptoms checked by an optometrist
- A sudden increase in floaters, especially accompanied by flashes of light or peripheral vision loss, can be a sign of retinal detachment. This is a serious condition that requires immediate medical attention to prevent permanent vision loss
- Bleeding into the vitreous (haemorrhaging) can cause floaters and be indicative of conditions such as diabetic retinopathy or a retinal tear
- Inflammation inside the eye (uveitis) can cause the release of debris into the vitreous, leading to the perception of floaters
- Eye infections or injuries can cause inflammation and debris in the eye, leading to the perception of floaters and flashes
- Some people who experience migraines might also see flashes or images of light, lasting from several minutes up to half an hour or more - these visual disturbances are usually temporary and are not related to any acute physical eye problems
- As we get older, the vitreous of our eye may also become more liquid, leading to the development of floaters. These present as tiny specks or worm-like shapes that float across the field of vision and are a normal part of the ageing process, but the possibility of retinal detachment still needs to be ruled out whenever new or changed floaters are noticed
When is a trip to the optometrist necessary?
Observing moving dots against a clear sky is typically harmless. However, if you notice a sudden change in your vision or experience new flashes or floaters, it's imperative to consult an optometrist as a matter of urgency. As discussed above, these vision changes could indicate a more severe eye condition and warrant immediate attention.
It is recommended that every Australian, from the time they start primary school, pay their optometrist a visit every year until age 18, then every two years as an adult, and then yearly again after turning 65, for a comprehensive eye examination.
To schedule an appointment with your local optometrist today, use our easy search tool here.
