The terms “Floaters and Flashes” have different meanings to different individuals. However, in ophthalmology they have very specific meanings. A floater is defined as an image seen by the human brain which is produced by a particle floating in the Vitreous Humour of the eye. It is not an image that is visible to other people. Usually patients have numerous particles floating about so the term used most often is floaters as opposed to floater.
Flashes are defined as flashes or streaks of light produced on the inside of the eye and visible only to the person(s) experiencing them. They are not real to the observer but are real to the patient. They are produced by trauma to the retina of the eye and sudden changes in the intra-ocular pressure. A classic example is the “seeing stars” phenomenon when one is punched in the eyeball.
As we get older most of will experience small, dark shapes that appear to float in our field of vision. These are called floaters as defined above. The shapes of these floaters may be round, ribbon shaped, oval or rectangular. These are floaters and they are particles in the vitreous humour of the eye. The vitreous humour is a jelly-like substance which fills the inside of the mammalian eye. The vitreous body is comes in contact to the retina of the eye. This is the light-sensitive tissue at the back of the eye which contains the rods and cones.
Floaters appear as if they are real images in the field of vision because they cast shadows on the retina which are transmitted to the brain. During an eye examination floaters become more obvious when the patient is asked to look at a clear back-ground. Examples of clear background include a bright blue sky, sheet of white or grey paper. Since floaters are “debri” floating in the eye, they move quickly when the eye is moved and they drift away when the eye stops moving. When a patient has many floaters it can interfere with vision. In extreme situations it can lead to blindness. Retinitis Pigmentosa is an extreme example. Some patients with floaters will barely experience any difficulty. Sometimes, floaters can come and go over many years.
In the image of the eye below floaters and flashes can be seen by the patient anywhere between the lens and the optic nerve.
Sometimes, small flashes of light may be seen by the patient with or without the appearance of floaters. Flashes are usually caused by the vitreous humour adjusting the pressure on the retina of the eye. The example given above (punch or blunt instrument trauma) characteristically brings about sudden changes which produce the flashes. This phenomenon (pressure changes) is also a normal part of the ageing process. In some patients flashes may last for a few seconds or several minutes. In other patients they may occur off and on for several weeks. For best visualization of flashes it is best to place the patient in a dark room. Some patients may say that they see flashes at night only on in poor lighting conditions.
Patients with Migraine headaches sometimes complain of flashes. These flashes often appear as jagged lines blocking an area of vision. These flashes are not related to the vitreous body but may be related to changes in intra-ocular pressure.
Normal and Abnormal: Floaters & Flashes.
Flashers and Floaters appear directly as a result of the normal aging process. As we age the intra ocular vitreous humour shrinks and is replaced with a more liquid fluid. The occurrence of this patho physiological process explains the formation, occurrence, distribution and symptoms associated with these changes. Hence, floaters appear in the watery vitreous humour. In some instances the shrinking vitreous separates from the retina, when this happens “posterior vitreous detachment” is said to have occurred.
This generally occurs in patients who are 55 years or older. These patients generally complain of one large floater and multiple flashes. Most of the time the floater disappears over some time and normal vision is restored. At other times, when the vitreous humour is more firmly attached to the retina, it may pull away the retina as it shrinks. This may cause bleeding and trigger a “shower” of floaters. This phenomenon is called a retinal tear. During retinal tear, fluid can cause the retina to be detached from the retina. Retinal Detachment is an ophthalmic emergency and the treating team must be notified immediately to prevent blindness. Immediate surgery is indicated.
As stated earlier floaters, flashes and posterior vitreous detachments may occur as normal aging or may be pathologically induced by trauma or other causes. The causes of floaters are discussed under the appropriate section.
Diagnosing Floaters and Flashes. Medically trained doctors and opthalmologists are trained to diagnose these disorders. Patients who complain of seeing flashers and or floaters should be referred to a doctor or an ophthalmologist. Changes in amount of floaters and flashers should also be referred to qualified practitioners.
