What cause floaters across at front of your eye when you are seeing white or black stars (floaters) what cause them? they're annoying aren't they?
For most people, floaters occur as they grow older. The vitreous humor thickens and clumps as we age, and floaters result from the clumped vitreous gel. Sometimes pregnant women see spots caused by little bits of protein trapped within the eye. Eye injury or breakdown of the vitreous humor may also cause spots and floaters.
When people reach middle age, the vitreous gel may start to thicken or shrink, forming clumps or strands inside the eye. The vitreous gel pulls away from the back wall of the eye, causing a posterior vitreous detachment. It is a common cause of floaters, and it is more common for people who:
are nearsighted;
have undergone cataract operations;
have had YAG laser surgery of the eye;
have had inflammation inside the eye. There are various causes for the appearance of floaters, of which the most common are described here. Basically, any way by which material enters the vitreous humour is a cause for floaters.
Vitreous syneresis
The most common cause of floaters is shrinkage of the vitreous humour: this gel-like substance consists of 99% water and 1% solid elements. The solid portion consists of a network of collagen and hyaluronic acid, with the latter retaining water molecules. Depolymerisation of this network makes the hyaluronic acid release its trapped water, thereby liquefying the gel. The collagen breaks down into fibrils, which ultimately are the floaters that plague the patient. Floaters caused in this way tend to be few in number and of a linear form.
Posterior vitreous detachments and retinal detachments
In time, the liquefied vitreous body loses support and its framework contracts. This leads to posterior vitreous detachment, in which the vitreous body is released from the sensory retina. During this detachment, the shrinking vitreous can stimulate the retina mechanically, causing the patient to see random flashes across his visual field. The ultimate release of the vitreous sometimes makes a large floater appear, usually in the shape of a ring. As a complication, part of the retina might be torn off by the departing vitreous body, in a process known as retinal detachment. This will often leak blood into the vitreous, which is seen by the patient as a sudden appearance of numerous small dots, moving across the whole field of vision. Retinal detachment requires immediate medical attention, as it can easily cause blindness. Both the appearance of flashes and the sudden onset of numerous small floaters warrant an ophthalmological investigation.
Regression of the hyaloid artery
The hyaloid artery, an artery running through the vitreous humour during the fetal stage of development, regresses in the third trimester of pregnancy. Its disintegration can sometimes leave cell matter.
Other common causes
Other causes for floaters include active toxoplasmosis, cystoid macular oedema and asteroid hyalosis. The latter is an anomaly of the vitreous humour, where by calcium clumps attach themselves to the collagen network. The bodies that are formed in this way move slightly with eye movement, but then return to their fixed position.
Tear film debris
Sometimes the appearance of floaters has to be attributed to dark specks in the tear film of the eye. Technically, these are not floaters, but they do look the same from the viewpoint of the patient. People with blepharitis or a dysfunctional meibomian gland are especially prone to this cause, but ocular allergies or even the wearing of contact lenses can cause the problem. To differentiate between material in the vitreous humour of the eye and debris in the tear film, one can look at the effect of blinking: debris in the tear film will move quickly with a blink, while floaters are largely unresponsive to it. Tear film debris is diagnosed by eliminating the possibility of true floaters and macular degeneration. Foreign matter passing through your field of vision. Migraine headaches ofter start this way. If you find yourself seeing black specks or feel like you are seeing little "strings" in front of your eyes you may have detached retina and should seek medical advice immediately. The inside of the eye is filled with a clear, gel-like substance called the vitreous. The vitreous helps maintain the shape of the eye and allows light to pass through to the retina. The retina is a thin, light-sensitive tissue that covers the inside back portion of the eye and works like the film in a camera. Floaters are small clumps of gel that form in the vitreous. Although they appear to be in front of the eye, they are actually floating in the vitreous and are seen as shadows by the retina.
The appearance of floaters may cause concern, especially if they develop suddenly. However, they are usually of little importance. As people get older, the vitreous shrinks and often separates from the retina. By the age of 50 years the vitreous has separated from the retina in about 50% of all people. As the vitreous detaches, it causes floaters. At first the floaters may be quite annoying, but the brain gradually learns to ignore them, and after several months they are hardly noticed. |
