Flashes & Floaters: Vitreous syneresis & posterior vitreous detachment
The vitreous is the jelly material that fills the back of your eye. When you are born this is a solid structure which is firmly attached to the retina at the back of your eye. As you get older, however, the vitreous starts to break down and becomes more liquid; this process can start in your late teenage years or, rarely, younger. This ‘liquefaction’ of the vitreous gives rise to pockets of fluid inside the gel which causes light to hit the interface between the two, and cast shadows on to the retina. These shadows are what we perceive when we see ‘floaters’.
As we get older still, the pockets of liquefied gel become more confluent (syneresis); they then break through the vitreous cortex – the outside layer of the gel that was adherent to the retina. This leads to separation of the gel from the retina. This event is called Posterior Vitreous Detachment (PVD).
PVD is very common over the 50 years of age but can occur earlier if you are short sighted (myopic). The symptoms of PVD are a sudden onset of floaters, often described as being like a cobweb, or frog-spawn. As the gel separates from the retina it can pull on it; this will set off flashes of light inside the eye.
Floaters are more noticeable with high contrast lighting or backgrounds – a bright sunny day, or a looking at a computer screen will make these more visible. The brain is very good at ‘filtering’ out this junk information but if you look for floaters you will find them!
Some people have significant troubles with numerous floaters and are unable to ignore them. Surgery can be performed to remove these. This operation is known as a vitrectomy – to remove the vitreous.
See vitrectomy video
As the vitreous gel separates from the retina, during Posterior vitreous detachment, there may be focal points of strong adhesion between the gel and the retina. The gel will pull on these points, as the eye swings back and forth, and can lead to a tear in the retina. A retinal tear is a dangerous situation as fluid from the vitreous cavity can get through the break, and then go under the retina leading to a retinal detachment. We call this type of retinal detachment ‘rhegmatogenous’ (from the greek rhegma meaning break or tear).
The symptoms of a retinal tear are big bright flashes of light in the eye – often compared to fireworks; accompanying these can be black floaters, like “black rain”, “dust”, or “flies”. If you get these symptoms it would be wise to see an ophthalmologist who can have a look at your retina.
Treatment of a retinal tear: The commonest ways to treat a retinal tear are with either a laser to create a scar around the tear like spot welding (laser retinopexy). This prevents fluid getting under the retina. Sometimes freezing treatment can be used – this is called cryopexy. Laser retinopexy can be done in clinic, whilst cryopexy often requires a short trip to the operating theatre, but is usually done under local anaesthetic.
Rhegmatogenous Retinal Detachment
A rhegmatogenous retinal detachment is an ophthalmic emergency. The aim is always to try to treat the detachment before the central portion of the retina – the macula – has detached. If the macula is still ‘on’ by the time you get to theatre, the chances that you will regain most of your vision are much greater. If however the macula has been detached for more than 24 hours you will likely not regain all your vision. Furthermore, patients who have had macula ‘off’ retinal detachments frequently report that the image from that eye is smaller and distorted. The analogy is like that of wallpaper – it never goes back on quite the same second time round.
Retinal detachment surgery
There are three main techniques used to treat rhegmatogenous retinal detachments:
Vitrectomy: This procedure is done most commonly under local anaesthetic – though a general anaesthetic, or sedation can be arranged. Entry into the eye is through micro-incisions that rarely require stitches. In this procedure the surgeon operates inside your eye to remove the vitreous gel. Once the gel has been removed, the fluid is removed from under the retina. The breaks in the retina are sealed with freezing or laser treatment. The eye is then filled with either an inert gas that slowly dissolves away over the next few weeks or silicone oil that will require a second operation to remove.
Retinal detachment video
Post-operative care: You may be asked to lie or sit in a particular position for a period after the surgery. The reason for this is to ‘put the bubble on the trouble’. The scar around the break in the retina takes 5 days to form. While this occurs there is a risk of fluid lifting the retina off again. The gas or oil bubble is used to block the hole in the retina to prevent this occurring. Talk to your surgeon about posturing requirements. Posturing is advised for 45 minutes in the hour 24 hours per day for the specified period.
While you have gas inside your eye you CANNOT fly or ascend to altitude. Depending on which gas is used, it will take between 3-8 weeks to disappear.
Bath/Shower: you can have a shower but the recommendation is to close your eye for the first week. You can clean the eye with cool boiled water and clean cotton wool balls.
Makeup: Please avoid eye make-up for the first week after surgery
Infection (1:1000) an infection inside the eye (endophthalmitis) is very rare but can lead to permanent loss of vision.
Bleeding: (1:1000) a major bleed in the wall of the eye is very rare but can lead to permanent loss of vision.
Failure or re-detachment: The recognised re-detachment rate in a number of series is 20%. At London Retina Consultants our most recent audit shows a 7.6% re-detachment rate. This means that a further surgery will be required to attach the retina.
Cataract: 60% of patients will require cataract surgery within 2 years of surgery, many require it sooner.
A macular hole is a vitreo-retinal condition where a hole appears at the middle of the patient’s vision at the fovea in the centre of the retina.
It is usually caused by abnormal adhesions between the jelly of the eye (vitreous) and the retina. As we get older, the vitreous frequently separates away from the retina in a process known as posterior vitreous detachment (PVD). In some cases however the vitreous is firmly stuck to the retina and traction from the gel pulls a hole. Patients frequently complain of difficulty with reading or seeing faces and there is often distortion at the centre of the vision.
This hole can be closed with surgery. Your surgeon will perform a vitrectomy (removal of the vitreous); a thin membrane on the surface of the retina is then peeled off (ILM peel); and the eye is then filled with gas.
You may be asked to “posture” after surgery: this involves looking or lying face down so that the gas bubble is in contact with the hole. This may be for a number of days. Not all surgeons advocate this however.
The vision will take some time to recover and is unlikely to be quite as good as it used to be. The distortion is usually much improved and there is more central detail than preoperatively.
An epiretinal membrane (also known as macular pucker, or cellophane maculopathy) is a layer of scar tissue that forms over the centre of the retina at the macula. This acts like all scar tissue does – which means that it contracts. This pulls the underlying retina into folds causing thickening and distortion of the retinal architecture. This in turn can cause distortion of a patient’s vision and blur.
Treatment is most commonly with surgery. Your surgeon will perform a vitrectomy – to remove the vitreous gel of the eye. The epiretinal membrane is then stained with a special dye. It can then be peeled off the surface of the retina.
The vision takes some time to recover; it can sometimes get transiently worse post operatively, as removal of the membrane causes inflammation and thickening of the retina (rather as the skin becomes red and swollen after removal of a sticky plaster). Over several months, however, the retinal architecture improves and the quality of vision with it.