Floaters and flashes
What are Floaters?
When the normal transparent jelly (vitreous) that fills the back of the eye contains opacities they cast shadows on the retina (the light sensitive membrane lining the back of the eye) which are seen as strands or spots, or cobwebs or insect like images which drift across the vision. These are floaters, sometimes called muscae volanties or flitting flies.
Floaters are not obvious all the time to most people but in bright light, when the pupil goes small, and against a pale background such as the sky,or a pale wall they are most evident.
Many people have some floaters especially if they are short sighted when the jelly tends to have more strands in it. As people, age the jelly naturally becomes more fluid in everyone. Sometimes the jelly develops watery spaces within it and collapses inward separating from the retina. When this happens (posterior vitreous detachment or (PVD), the person may experience a sudden shower of floaters. These are usually simply opaque strands where the jelly was attached to the back of the eye round the optic disc, the point of entry of the optic (sight) nerve. Often these floaters are oval, circular or C shaped.
Sometimes there is a small amount of bleeding which again presents as floaters. Blood can come from tiny blood vessels on the surface of the retina, in which case it is usually transient, but in about one case in twenty, the attachment of the jelly to the retina is strong enough to result in a tear in the retina. The hole so formed can lead to a retinal detachment which is sight threatening so it is important that all people who experience a sudden onset of new floaters have a thorough examination by an ophthalmic specialist. If a hole is found before detachment of the retina occurs laser can be used in outpatients to seal it up which in the vast majority will preserve sight and prevent the need for an operation.
If the retina is examined and no hole is found there is an extremely low chance of new holes forming which might lead to retinal detachment and we would not normally recommend further examinations. However, if you should experience a sudden onset of new flashers and floaters or if any part of your peripheral seems to be missing or dull you should be seen within 24 hours by an ophthalmologist.
The floaters following PVD usually become less evident with time but they will not disappear altogether. We do not offer treatment for removal of floaters except in exceptionally rare circumstances when they are visually incapacitating when an operation can be done to remove the jelly and floaters.
At the time of the initial vitreous detachment some people experience a single brief flash of light. Most people do not notice this.
After PVD it is very common for people to experience momentary silver streaks of light or dusk or in darkness, particularly on eye movement. These often become less apparent over a few months but they have no sinister significance and therefore on their own do not warrant further specialist attention.
Finally, floaters can occur in a number of other eye diseases such as diabetic retinopathy and uveitis.
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