What are floaters?
What are floaters and degenerative vitreous?
Floaters, also known as symptomatic vitreous opacities, are shapes that people can see drifting across their vision and are due to ‘bits’ floating in the vitreous gel inside the eye. They can come in a variety of forms such as small black dots, short squiggly lines or even large cobweb shapes. Shortsighted people tend to suffer from them more and at a younger age and they increase as we get older. They can interfere with vision by getting in the way of what you want to look at, but some floaters and degenerative vitreous changes can also cause a non-specific reduction on the quality of vision, particularly contrast sensitivity.
Floaters can occur with a posterior vitreous detachment (PVD) or without a PVD, the latter being commoner in young people with myopia, although they are more likely to get a PVD at a younger age as well.
Floaters are usually the result of degenerative vitreous, which is a normal ageing change in the vitreous gel as it becomes liquefied (see next). In some people, particularly if short sighted, the vitreous can liquefy at a younger age, causing floaters to be seen at an earlier stage in life. Floaters are more noticeable in certain lighting and background conditions, such as looking at a white wall or ceiling, or at a white background on a computer screen. This is because light coming into the eye is obstructed by the solid strands and clumps in the vitreous, and casts a shadow on the retina. Degenerative vitreous may allow the clumps and strands to settle to the bottom of the eye with gravity when you are upright, but when you are lying down looking up at the ceiling the floaters may come right into the centre of the eye and be more noticeable. Some floaters can have a ‘snow-globe’ effect, becoming very noticeable when you get up from lying down, or when you move the head or eyes briskly.
What causes Floaters?
The eye is filled with a gel-like substance called vitreous. The vitreous sits behind the pupil and lens. The vitreous gel is made mainly of water with a collagen meshwork held together by hyaluronic acid. As we get older, a process known as vitreous syneresis occurs; the meshwork breaks down and liquid lakes form. The solid meshwork of the gel separates out forming clumps and strands. The clumps and strands casts shadows onto the retina, which we see as floaters.
In 70% of people, by the age of 70, the liquefied vitreous gel can lose its support framework causing it to collapse. This process is known as a posterior vitreous detachment (PVD). As the vitreous gel peels away from the retina, it can cause people to see intermittent flashes of light. The flashing light will usually subside over 4 to 12 weeks, but in some patients it may take a little longer. When a posterior vitreous detachment occurs people often become aware of a cobweb or net curtain-like floater that can be quite intrusive at first.
Bleeding inside the eye can also cause floaters, and inflammation in the eye is a rarer cause of floaters. Retinal pigment from a retinal tear or detachment can also cause floaters.
Can Floaters have complications?
What complications of floaters can occur?
In the vast majority of cases floaters are harmless and represent the normal, natural (although occasionally annoying) aging change of the eye. They usually become much less obvious with time as the brain adjusts and eventually filters them out.
Sometimes, during the development of a posterior vitreous detachment, the vitreous gel can be stuck to a patch of retina and cause a tear in the retina as the gel pulls away. If the seal of the retina against the back of the eye is broken, fluid can start to track in through the tear, behind the retina, causing it to detach from the back of the eye a little like wallpaper peeling off a wall. This uncommon event occurs in approximately 1 in 10,000 of the population in general. Usually, if a tear develops in the retina people experience a very marked shower of floaters associated with flashes of light in their peripheral vision. The light is usually persistent and may occur in daylight, although most people notice it in dim lighting. Some people notice a curtain effect coming in from their peripheral visual field. This requires urgent attention by an eye doctor.
Options, risks and benefits
Since floaters do not harm the eye, and in the vast majority of people do not cause a significant problem, we generally do not need recommend any form of treatment for them. It is possible to carry out an operation to the eye to remove the vitreous gel (vitrectomy), which will also remove the floaters. Occasionally, this course of treatment is useful in people with very severe floaters or in those who are cannot adapt to them. Modern day vitrectomy with smaller incisions and finer instruments has a lower risk of retinal tears and detachments during surgery, but no surgery is without risks.
A floater only vitrectomy, FOV, also known as a core vitrectomy, only removes the body of the gel containing the floaters but does not peel away gel from the retina or the back surface of the lens. It does not separate the vitreous attachments from the retina, reducing the risks of a retinal tear or detachment during the operation. It also leaves the vitreous gel on the back surface of the lens, which is thought to reduce the risk of early onset cataract.
The residual vitreous attached to the retina will separate at some point in the future, and there is a risk of retinal tears or detachment when this occurs. It may be months or years after the FOV. Separation of the vitreous may be associated with a new onset of floaters, but these may be different to the ones for which surgery was performed.
A complete vitrectomy removes as much vitreous gel as possible, including peeling it away from the posterior surface of the retina. This carries a risk of retinal tears or detachment during the surgery, but reduces the risk of developing a tear later on as there is no gel to separate spontaneously. Although this is not necessary to remove the floaters, it does reduce the risk of further floaters months or years in the future when the attached membrane of vitreous gel separates naturally.
Questions I usually ask
· Are you having difficulty seeing the TV screen clearly or reading subtitles?
· Are you struggling to recognize bus numbers or people’s faces until they are really close?
· Is it difficult reading small print unless the lighting is really bright?
· Do you feel that your glasses aren’t giving you clear vision, and your optician has said that
they can’t improve with a new prescription?
· Do you have hazy vision?
· Is it difficult to see clearly when you are driving?
· Do you have glare with night driving or in bright lights (such as supermarket lighting)?
· Are you having difficulty reading music?
· Is your vision affecting your work?
· Do have a particular hobby or interest that your vision is affecting?
Options, risks and benefits
Vitrectomy surgery, as with any surgery, carries with it the risk of various complications and it is for this reason that we generally do not recommend it for the treatment of all floaters.
The most common side effect of the vitrectomy surgery is the development of cataract at an earlier stage than it would have done otherwise. Rarely this can be weeks or months after surgery but more commonly this may come on 2-3 years after the operation. This is one of the reasons we try to avoid this approach in younger patients.
About 4% of patients develop a retinal detachment after the surgery. In this situation, further surgery is required to reattach the retina, which can sometimes lead to reduced vision in the eye afterwards.
The most severe complication from this kind of surgery is an extremely rare occurrence (approximately 1 in every 1000 cases) of blindness in the eye, usually because of a severe bleed during surgery or an infection in the eye after the operation. It is important that patients are aware that there is a chance, albeit very small, that it could happen.
Anaesthesia for Vitrectomy surgery
Most vitrectomy surgery can be done with just local anaesthetic, using using a sharp needle or blunt cannula technique for injection to numb the eye (you will be awake during surgery).
Some patients are not good candidates for local anaesthesia – either they are unable to lie still for the required time, or they are very nervous or simply have a fear of being awake whilst they have an eye operation. In such situations I can arrange for you to have general anaesthesia as long as your general health can tolerate it – the decision is one that we make with the anaesthetist looking after you to make sure you are safe at all times. I also have the option of offering light sedation instead of full general anaesthesia.
How long do I have to stay in hospital for vitrectomy surgery?
Vitrectomy surgery is usually done as a daycase procedure. This means that you will be in hospital for a few hours, and can go home the same day. Often, patients can also go home the same day after general anaesthesia, but this depends on how well you recover.