The abrupt onset of new “floaters” and/or “flashes” is a common reason people come in for an eye examination. In fact, if you call the office and report the new onset of floaters and/or flashes, we will recommend you come in right away for an examination. Most of the time the symptoms do not indicate a serious problem, but only a dilated eye exam can distinguish between those who do and those who do not have a vision threatening problem.
What are flashes?
Brief arcs or flashes of light that occur in one eye usually indicate that something is pulling on the retina. Usually, this is the vitreous gel. Rare flashes that are noticed with eye movements while in a dark room are generally not a concern. However, many flashes happening rapidly in one eye can be a sign the retina has been pulled to the point of being torn – especially if they are followed by “floaters.”
What are floaters?
Any opacity in the vitreous space of the eye will cause a shadow that we perceive as floaters. The vitreous is the clear, gel like substance that fills the back portion of the eye. The vitreous gel collapses upon itself slowly with age in a process called “syneresis.” This type of floater is usually subtle and not associated with flashing lights. They can develop even in childhood, especially in near sighted individuals. People often notice these floaters upon looking up at a clear blue sky or walking into a brightly lit white room. The peripheral vision should remain fully intact.
The vitreous can shrink enough that most individuals experience a posterior separation of their vitreous sometime in their fifth to seventh decade. This will happen in one eye at a time, and can be quite disturbing to the individual – or can go unnoticed. This is called a “posterior vitreous detachment or PVD,” and is the most common reason we see people with new floaters.
When the vitreous is trying to pull away from the retina, it often causes the sensation of flashes of light. When the vitreous does pull away, the strands that connected it to the back wall of the eye now float in front of the retina – causing floaters. Also, a retinal vessel can also bleed when the vitreous separates, causing even more dramatic floaters. The real problem is that when the vitreous is in the process of separation, it is the most likely time a person will suffer a retinal tear. Also, the symptoms of a retinal tear and the posterior vitreous detachment are indistinguishable. This is why we need to dilate and examine all individuals with new onset flashing lights and/or floaters.
If most flashes and floaters are from symptomatic posterior vitreous detachments, why do we have people get a dilated eye exam?
This is because the same symptoms can be present with the onset of a retinal tear. This could lead to retinal detachment, a potentially blinding complication. In fact, the separation of the vitreous is the most common catalyst for a retinal tear. If a retinal tear is found, it can be treated to try to prevent a partial or full retinal detachment. The retina is the thin nerve tissue lining the back of the eye that senses light. It is our retina that gives our eye vision.
If the retina does tear, a person often experiences flashing lights followed by new floaters (from the retina bleeding). There is no pain. The floaters are often dramatic, like hair in the eye or a flock of birds. Sometimes the vitreous gel is so full of blood that a person can barely see through it. The goal is to catch the problem at the level of the retinal tear and to avoid retinal detachment if possible by treating the tear with laser.
If the retina detaches, it comes away from some of its blood supply, and a person observes a black curtain coming over the vision in one of their eyes from any direction. You can not see anything through this curtain. It is critical to diagnose and repair a retinal detachment while the central vision remains intact. This can result in the best visual outcome. If the central vision detaches, the higher acuity central vision may not return even with successful reattachment surgery. Retinal detachment surgery is usually performed by Ophthalmologists who specialize in retinal surgery.
We hope this information helps you to understand why it is important to examine all individuals with new onset flashing lights and floaters. The most common cause is a benign posterior vitreous detachment, but a retinal tear must be ruled out. Also, it is not uncommon to develop some scar tissue over the surface of the retina called an “epiretinal membrane” after separation of the vitreous. This membrane can affect vision, but most often is not noticed by the patient. It can be treated surgically if needed.
You can take comfort in the fact that floaters from posterior vitreous detachments cause annoying symptoms variably in individuals for days to months – but then are almost always successfully ignored. Any new flashes/floaters warrant an additional examination.