Flashes, Floaters and Spots
Occasionally, as we look at the sky or at a blank wall, we notice small spots that look like grey particles, floating in the visual field; they can be shapes such as loops, lines or cobwebs and they seem to move somewhat with the eyes.
Sometimes we are aware of short flashes of light as well. Both floaters and flashes are usually benign and are more annoying than serious. However, a sudden onset of floaters or flashes of light can be signs of something more serious; we will discuss what and when to report to your eyecare practitioner later on.
Floaters are actually shadows cast onto the retina by irregularities and strands found in the vitreous humour, the thick, gelatin-like substance that fills the major part of the eye and keeps it from collapsing.
A developing fetus has a network of blood vessels that nourish the crystalline lens inside the eye, but before birth, this disintegrates and mostly disappears. In many cases, the spots we see floating around are remnants of this network, small bits of tissue that didn’t dissolve. Also, floaters can increase with age, because the usually transparent vitreous tends to lose its smoothness and can become lumpier with time; the connective tissue within the vitreous body can also become more obvious as well.
These small bits of leftover tissue and the clumps and strands that have become more visible over time are normal, although they can become annoying if they manage to float into the direct line of vision.
People who might notice floaters include
- Myopes (people who are nearsighted)
- People who are pregnant
- People who have had cataract extraction surgery
- People with a history of other eye surgery
- Those with a history of iritis or iridocyclitis (episodes of inflammation in the eye)
- Athletes or others who have had head injuries or impacts
- Those with a history of other head and/or neck injuries, as in automobile crashes
- Those with a history of circulatory problems, such as diabetes
- People who suffer from migraine headaches
Like floaters, flashes are usually benign as well, but they can signal that something more serious is occurring, such as tearing of the retinal tissue or a retinal detachment.
(Illustration of retinal detachment shows retina separating from its backing and falling downward; this type of detachment would cause sparks of light to appear in the lower visual field.)
When something stimulates the nerve cells of the retina to respond, they do so by sending a signal to the brain that there is light; this is the only way these cells can respond to any such stimulus, even if there is no light at all. These can be perceived as discreet small pinpricks of light, or can be described as “a shower of sparks,” or a “sparkling curtain.”
People who have migraine headaches sometimes experience flashes and floaters, but these differ somewhat from those that may signal more serious problems, in that they may appear to twinkle, change colors or expand in size over 15 to 20 minutes before disappearing and the headache begins.
Flashes of light, particularly if they seem to be located in the lower part of the field of view can be a sign of retinal detachment; if you experience this, see an eyecare practitioner as soon as possible, as this is a sight-threatening emergency. (The flashes appear to be in the lower field of view because the upper retina perceives vision opposite to its location.) As the retinal nerve cells are pulled away from their backing, they cause flashes of light as they separate. A sudden onset of new flashes or new floaters that lasts longer than 15 minutes requires immediate attention. A small retinal tear can progress into a full detachment over time; if the cells are no longer attached to their source of nutrition, they will die and cause permanent vision loss in the area of the detachment.
The vitreous humour, sometimes referred to as the vitreous body, is firmly attached to the retina and other structures in the back of the eye; with age, these attachments become weaker and it is not unusual for the vitreous to detach itself, especially around the head of the optic nerve. This is known as a posterior vitreous detachment (PVD) and is not itself serious, except that it must be checked and a more serious retinal detachment ruled out. A PVD is painless and does not cause any effect on the vision. A PVD may cause separate floaters or even one that is shaped like a ring or part of a ring.
If the floaters are bothersome, it may help to look quickly up and down and from side to side to allow the floaters to drift away from the visual axis where they are more noticeable.
There is no surgical procedure to remove floaters, but they do often fade over time, probably because they eventually sink to the bottom part of the eye. Brief flashes caused by a PVD should settle down within a few weeks to a few months without disturbing the vision further.
New Symptoms: See Your Eyecare Practitioner
Any new-onset flashes or floaters, or a sudden increase in their location or number is a sign that needs to be evaluated by an eyecare practitioner without delay, to rule out retinal detachment. 'A detached retina is a sight-threatening emergency and is time-sensitive;' the longer the cells go without their nutritional support, the less likely it is that they will survive. The detached portion of the retina can sometimes be re-attached with surgery, which at the least should stabilize the damage and prevent further progression.
Most flashes and floaters are not serious, however, and require no treatment at all; the key to knowing which is which depends on being aware of the state of your normal vision. If you have never experienced any flashes or floaters, and suddenly there is a significant number of them, that requires checking. This is particularly true if there has been a fall, a blow to the head, or perhaps even a minor fender-bender in the car.
If you are not sure if your situation is serious, just call and ask; much better to be over-cautious than to risk vision loss.