Many people, especially older people, complain of seeing spots, threads, or other objects move back and forth in front of their eyes. They are called floaters and could appear black, grey or cloudy. They are more noticeable in bright light and can be disturbing especially at the onset.
Floaters are mostly gel-like material, cells or pieces of tissue that are suspended in the clear gel-like fluid at the back of the eye known as vitreous. People, however, get the impression that these objects are in front of their eyes. This is because the light that enters the eyes shines on the objects and casts shadows on the retina. The shadows (images) are then projected into space giving the impression that the objects are in front of the eyes.
Causes of Floaters
Some of the causes of floaters include posterior vitreous detachment, retinal detachment, inflammations in the back of the eye and bleeding into the vitreous.
Posterior Vitreous Detachment
Posterior Vitreous Detachment (PVD) is a condition in which the vitreous separates from the retina. It is often caused by age-related changes in the eye. When we are young, the vitreous is gel-like, but as we get old, it gradually liquefies and shrinks and may begin to pull away from the retina. PVD is, therefore, more common in the aged. Most people above 60 years tend to have it, at least in one eye.
In addition to floaters, people with PVD may experience flashes of light caused by the stimulation of the retina.
Most PVD does not harm the eyes. In a few people, however, it may cause a hole or tear in the retina, which could result in retinal detachment.
Retinal Detachment
This is the separation of the retina from its supportive tissue in the eye. In retinal detachment, floaters and flashes of light increase significantly beyond what is seen in vitreous detachment. There may be visual field loss. This is described by some patients as seeing a curtain drawn over a certain portion of their visual field.
Retinal detachment is an ocular emergency. It results in permanent loss of vision if not repaired promptly.
Inflammation in the Back of the Eye
Inflammation in the back of the eye such as seen in diseases like posterior uveitis, vitritis, cytomegalovirus retinitis, may cause vitreous cells to be suspended in the vitreous giving the symptom of floaters or spots. Floaters, in this case, are not usually accompanied by flashes of light. Vision, however, may be reduced.
Bleeding into the Vitreous (Vitreous Haemorrhage)
Sometimes the retinal blood vessels may rupture in response to an inflammation in the back of the eye and bleed into the vitreous. Blood cells and tissue suspended in the vitreous can give the impression that there are spots in the field of vision. Some of the conditions that may cause bleeding into the vitreous include diabetic retinopathy, central retinal vein occlusion, age-related macular degeneration, trauma etc. Floaters, in this case, are usually accompanied by reduced vision.
Treatment of Floaters
The treatment recommended for floaters depends on the cause.
Floaters due to posterior vitreous detachment (PVD) usually do not require treatment. Generally, patients are assured that they are harmless and are advised to ignore them. Over time some get used to the floaters. However, treatment may be considered for large PVD that impairs vision. A surgical procedure known as vitrectomy may be done to remove the vitreous and replace it with a sterile solution that helps keep the eyes in shape. The risks associated with this surgery, however, outweigh the benefits and many eye surgeons usually do not recommend it. Another treatment option for PVD is laser vitreolysis. This is a procedure that involves the use of lasers to break up floaters and make them less visible.
Floaters due to retinal detachment is an emergency condition that requires urgent surgery to prevent permanent vision loss.
Floaters due to inflammation and bleeding in the back of the eye are managed by treating the underlying conditions.
On a final note, while floaters are usually associated with harmless ageing changes in the eyes, they can be caused by vision-threatening conditions such as retinal detachment and inflammation or bleeding in the back of the eyes. It is, therefore, necessary to see your eye doctor for proper diagnosis and care when you notice them. This is particularly important if the floaters are numerous or are accompanied by pain, continuous flashes of light and/or visual field loss.