What are "floaters"?

Most of the volume of the inside of the eye is filled with a jelly-like material called the 'vitreous' (meaning 'glassy'). The vitreous is tethered to a structure near the front of the eye called the 'ciliary body', to the retina along the line of the retinal blood vessels and to the optic nerve head at the back of the eye (figure 1).

Early on in life the vitreous is quite solid and rather immobile, but as the eye ages the vitreous develops splits in its structure that fill with fluid. This allows part of the vitreous to become more mobile. In most people, the vitreous eventually separates from its moorings to the optic nerve head and the retina allowing the back surface of the gel to float forwards. This event, called posterior vitreous detachment' (figure 2) can be precipitated by trauma, such as a blow to the head or to the eye, or can be a natural accompaniment of aging.

Figure 1

Figure 2

Floaters are particles embedded in the vitreous. Most are harmless remnants of a primitive blood vessel system that supplies the developing front of the eye during embryonic life. Whilst the vitreous is solidly in place the particles are immobile. They cast shadows on the retina but, because the shadows are always in the same place, the visual system adapts to their presence and they are rarely visible to their owner.

As the vitreous becomes more mobile the floaters start to move around more and their shadows move. This is when they become noticeable.

New floaters can arise and in the case of any sudden or rapid onset of floaters the person should seek the advice of an ophthalmologist (a doctor specialising in eye problems) without delay. If the vitreous detaches from the retina, the retina can be torn and bleed. A sudden shower of tiny black floaters may result. Inflammation in the eye can also produce an increase in floaters. When the vitreous detaches from the retina it can pull an arc or a ring of pigment from around the optic nerve head. This 'Weiss ring' floats forward almost directly into the line of sight. It is not dangerous at all but it can be particularly annoying. Sometimes people adapt to the presence of a Weiss ring over two or three months. Actually the term 'ring' is erroneous as less than a third of these floaters are complete rings!

The further forward the floaters are in the eye, the bigger the shadow they cast. A floater that looks small to the observer but that is near the front of the vitreous may seem very big to the subject, and vice versa.

How are floaters treated?

Treatment of floaters depends somewhat on their cause. Obviously, any underlying eye disease must be managed appropriately if present. For the floaters themselves there are three options:

1) Do nothing and put up with them;
2) YAG laser vitreolysis;
3) Surgical vitrectomy.

Laser treatment works best for fairly large, dense, central floaters. The large floater(s) are broken up into very small ones the annoyance value of which is usually much less. The Weiss ring floaters are often particularly good ones to treat by this method because of their size and their position in the field of vision, and thus their annoyance value, and because they are usually well clear of both the retina behind and the lens of the eye in front. Very diffuse, cloud-like, floaters and very tiny, fast moving, floaters are usually not suitable for laser treatment.

The success rate rather depends on the size, density and location of the floaters in the eyes, but if they can be lasered then there nearly always will be an improvement.

Is the surgical treatment of floaters safe?

The procedure is very safe, but not totally safe! There is an outside chance of incidentally damaging other structures in the eye due to the acoustic shock waves that are generated by the impact of the laser energy on the floaters. Both retinal detachment and cataract have rarely been reported. Retinal detachment is, of course, potentially sight threatening but can usually be repaired successfully. Cataract is eminently treatable although there is still a very small risk of sight-threatening complications in cataract surgery. Cataract following laser treatment occurs immediately.

If the floaters are unsuitable for laser treatment then the only other management option is surgical vitrectomy. This involves cutting the vitreous up inside the eye and sucking it out. It is very invasive and carries significant risk to sight, including infection inside the eye, which is potentially blinding, irreversible damage to the retina, and the inevitability of premature cataract that develops over months or a few years. It is rarely performed for floaters and only then if they are visually disabling.

C S Bailey BSc FRCS DO CertLRS, 99 Harley Street  London W1G 6AQ. Tel: +44 (0)207 935 1010  Fax: +44 (0)20 7084 7729