Although floaters are seen in the field of vision, they are actually caused by tiny clumps of gel or cells in the vitreous gel, the normally clear jelly that fills the cavity of the eye. These clumps or cells cast shadows on the retina, the light sensitive tissue lining the back of the eye. These shadows are then perceived as floaters in the field of vision.
Flashes result from tugging of the retina by the vitreous gel. This traction produces mechanical stimulation of the photoreceptors in the retina, leading to a sensation of flashing light in the eye.
Floaters refer to the ‘flying objects’ that are seen moving in the field of vision. They may appear like flies, dots, lines, cobwebs or floating bugs, and are more prominent when seen against a plain background such as the clear blue sky or a white wall. Floaters move with eye movements. Many individuals who experience floaters also have flashes of light.
Flashes are usually seen as twinkles or lightning streaks flashing in the eye. They are typically seen in the side of the field of vision. They are more prominent in a dim environment and can sometimes be seen even when the eyes are closed.
Floaters and flashes by themselves are relatively harmless. However, they may be warning symptoms of a number of eye conditions, some of which are serious and potentially blinding. It is therefore important for anyone with floaters or flashes, especially if they are new, to see a retinal or eye specialist immediately to exclude these conditions.
Floaters and flashes may be associated with the following conditions:
Posterior Vitreous Detachment
The vitreous gel that fills the cavity of the eye is attached to certain parts of the retina and the optic nerve head. Like many other parts of the body, it degenerates with age. With increasing age, the vitreous gel gradually liquefies and finally collapses forward. As it collapses, the back part of the vitreous gel tugs on the retinal tissues where it is attached before finally pulling away from the retina. This condition is called posterior vitreous detachment (PVD).
During PVD, the tugging action of the vitreous gel causes flashes at the side of the vision and floaters are formed by clumps of tissues that have been pulled off from the retina or optic nerve head. PVD itself usually requires no treatment. However, in some cases, it may cause a retinal tear or retinal detachment.
Retinal Tear and Retinal Detachment
A retinal tear may occur following PVD especially in areas where the vitreous gel is more adherent to the retina, such as in an area of pigmentation or lattice degeneration. Traction by the vitreous gel on the retina causes the thin retinal tissue to tear. In some cases, the retinal blood vessels may also be torn, causing bleeding into the vitreous gel which are seen as floaters by the patient.
Most retinal tears have to be treated as soon as they are detected to reduce the risk of fluid leaking through the tear to cause a separation of the retina from its underlying eye wall in a condition called retinal detachment. If left untreated, a retinal detachment usually leads to permanent blindness.
Other conditions that are often associated with floaters and flashes include high short-sightedness, inflammation of the eyes, eye injury, history of cataract surgery or YAG laser posterior capsulotomy, and the presence of systemic diseases such as diabetes mellitus.
Although floaters and flashes may sometimes resolve on their own, it is very important for individuals who experience these symptoms to consult a retinal or eye specialist for a thorough retinal examination. This is to rule out potentially sight-threatening conditions such as retinal tear and retinal detachment. Timely detection and treatment of retinal tear and/or retinal detachment is crucial to preserving sight.
If there are no sight-threatening conditions associated with the floaters and flashes, no treatment is usually necessary. However, individuals with floaters and flashes should monitor the severity and/or frequency of their symptoms. If there is a sudden increase in the number of floaters or flashes, or if there is disturbance in the vision or visual field, they should consult their retinal or eye specialist immediately.