The retina is a structure at the back of the eye which is important for sight. When two layers of the retina become separated, it is known as retinal detachment (RD). It is a very serious eye condition and can cause severe visual impairment if it is not treated promptly. However, with rapid diagnosis and treatment, which is usually surgery, the outlook (prognosis) may be very good for some types of detachment.
Understanding the retina
Light enters the eye and is focused on the retina by the lens. The retina produces a picture which is then sent to the optic nerve which transports the picture to the brain. If the retina is damaged or not in its correct position, a clear picture cannot be produced.
The macula is the small area of the retina where your central vision is formed. It is about 5 mm in diameter. The macula is the most densely packed with rods and cones. In the middle of the macula is an area called the fovea, which only contains cones. The fovea forms your pinpoint central vision.
The tiny blood vessels of the choroid bring oxygen and nutrients to the retina. Bruch's membrane is a thin protective barrier between the choroid and the delicate retina.
When you look at an object, light from the object passes through the cornea, then the lens and then hits the retina at the back of the eye.
What is retinal detachment (RD) and what causes it?
RD occurs when the inner layer of rods and cones separates off from the RPE. The light-sensitive cells lose contact with their nourishing layer and eventually start to atrpohy and die.
The separation can happen in three different ways:
Rhegmatogenous retinal detachment
In this type of RD a hole or break develops in the retina. This can allow fluid from the jelly-like centre of the eye (the vitreous humour) to creep in between the two layers of the retina (the light-sensitive cell layer and the RPE). This causes these two layers to separate (detach). This is the most common type of RD.
The most common cause of the retinal break is a posterior vitreous detachment. This is a very common condition of older people which occurs when the vitreous (the jelly like substance filling the globe of the eye) shrinks and pulls away from the retina. A high proportion of people aged over 60 years have a detached retina. However, in most cases the detachment will not damage the retina. Vitreous detachment leads to retinal tear in 10-15% of cases.
Retinal breaks are also more likely with the following:
- Near-sightedness (myopia). The greater the myopia, the greater the risk.
- Cataract removal. A cataract is clouding of the lens of your eye. The risk is greater if the lens is not replaced when the cataract is removed.
- Previous RD. Having had RD in one eye increases the risk of RD in the other eye.
- If you have Marfan's syndrome.
- Older age. Most cases of RD occur in people over the age of 40 years.
- RD is becoming increasingly common in children, due to injury from contact sports and leisure activities such as paintball.
Traction retinal detachment
Inflammation, eye surgery, eye infection or eye trauma can cause scar tissue (fibrous tissue) to form in the eye between the vitreous and the rods and cones. It can tug on the rods and cones, causing them to lift off the RPE. This is seen as a complication of inflammatory conditions such as uveitis.
Exudative retinal detachment
In this type of RD, fluid seeps out of blood vessels in the retina into the space between the retina and the RPE. This can occur as an uncommon complication of various conditions such as very severe high blood pressure, certain cancers and certain types of uveitis. Exudative RD generally resolves with successful treatment of the underlying disease, with very good recovery.
What are the symptoms of retinal detachment (RD)?
Possible symptoms of RD include:
- Flashing lights. Initially, you may notice flashing lights in your vision. This is noticed in 6 out of 10 people with RD and is most obvious in dim lighting and in side (peripheral) vision. It is thought to be caused by the retina being tugged and can be a warning sign.
- Floaters. These typically appear as one or more black moving dots in your vision. Sometimes they appear like cobwebs or curved shapes. The presence of floaters does not necessarily mean that you have RD, as floaters are very common. However, if you have any new floaters, a sudden increase in size and number of floaters and, in addition to floaters, you have a sensation of flashing lights then see your doctor urgently.
- Vision loss. You may notice shadowing in your peripheral vision, cloudy vision or loss of vision like a curtain coming over your eye. This is a sign of the retina actualy detaching and you should seek medical help at once.
- Early RD or a tear in the retina causes no symptoms and is detected on routine eye checks.
It is very important to see your doctor or optician immediately if you have any of these symptoms. If it is RD, the quicker it is treated, the better the outcome.
Are there any complications?
If retinal detachment (RD) is not treated promptly, it can lead to severe visual impairment in the affected eye. Occasionally the second eye is also affected.
How is retinal detachment (RD) diagnosed?
RD is diagnosed by an eye specialist using a special lamp to look into the back of your eye. The specialist can also check your vision.
If your GP suspects RD from your symptoms or their examination, you should be referred immediately to an eye specialist who can confirm the diagnosis and arrange treatment. The specialist will need to put some drops into your eye to open wide (dilate) your pupil so they can see the retina properly. These drops will cause a temporary blurring of your vision, which wears off over a few hours.
There are usually no other tests required to diagnose RD.
If the doctor cannot see into your eye properly - for example, if you have a clouding of the lens in your eye (a cataract) - the following may be done to view your retina:
- An ultrasound scan of your eye; or
- An eye scan called optical coherence tomography.
What is the treatment for retinal detachment (RD)?
Treatment is usually needed urgently. The sooner RD is treated, the better the outcome. In particular, it is best to fix an RD before it extends to affect the macula - the most important, central, seeing part of the retina.
The aim of treatment is to persuade the retina and the RPE to stick back together again, whilst sealing any tears to stop them from spreading and worsening.
There are several procedures that can be used to achieve these aims. More than one procedure may be used for the same person, depending on circumstances. The procedure or procedures that are done depend on the size, exact site, duration, severity and type of RD.
The procedures that may be considered include the following:
Treatment of retinal breaks with a laser or by freezing
A retinal break can be fixed with a fine laser or by freezing (cryotherapy) of the break. This may be sufficient if no fluid has started to seep under the tear. Treatment is in a hospital clinic using local anaesthetic drops. It seals the break, rather like 'welding' the layers back together.
This is an operation done under general or local anaesthesia. A small piece of silicone is stitched next to the outer wall of the eye (the sclera) over the site of the retinal tear. This pushes the sclera (and therefore the retina) inwards against the detached segment. This procedure is called scleral buckling because the sclera is 'buckled' inwards by the silicone. In some cases a band of silicone may be placed all around the outside of the eye, like a belt.
During the operation, some of the fluid that has built up behind the retina may be drained away. This can help the retina to re-attach better. However, if the fluid is not drained away at the time of the operation, it will gradually become absorbed back into the bloodstream.
Once the silicone or plastic buckle is in place, a gas bubble may be injected into the vitreous cavity to keep the retina flat up against the RPE so that it can re-attach. The gas bubble gradually disperses over a few weeks.
The silicone buckle is usually left on the eye permanently. Someone looking at you cannot see the buckle, as it is stitched to the sclera somewhere towards the back of the eye.
Scleral buckling may be done in addition to laser or freezing treatment to fix a retinal break.
This may be done under local anaesthetic. The eye specialist injects a gas bubble into the vitreous cavity of the eye. The bubble pushes the detached part of the retina flat back up against the RPE. This then allows the retina and the RPE to re-attach permanently.
The gas bubble gradually disperses and goes over a few weeks.
For this treatment to work, you must keep your head in a set position for most of the time for a few weeks, to encourage the bubble to sit in the right spot. Some people find this very uncomfortable and so pneumatic retinopexy may not be suitable for everyone. It is most commonly done for RDs in the upper part of the retina. For this, the position needed is for your head to be down and forward to allow the bubble to rise and push gently over where the RD is situated. This head positioning can be tedious and hard work for the few weeks that it may be needed until the retina is firmly attached back to its proper place.
Pneumatic retinopexy may be done in addition to laser or freezing treatment to fix a retinal break.
This is done under general or local anaesthesia. The gel-like substance called the vitreous humour is removed. The space left is then filled with a gas liquid or oil which pushes the retina back into place. The gas eventually disperses but is replaced by natural body fluid made in the eye.
A scleral buckle may be applied at the same time as a vitrectomy is performed.
After any of these treatments you will usually be given antibiotic and steroid drops to prevent infection and soothe inflammation. You may also need drops to lower the pressure in your eye and to relax the muscles of the iris.
After any treatment, if you experience significant pain or deterioration in your vision, you must inform your doctor immediately.
What is the outlook (prognosis)?
This depends on several factors:
- The length of time that the retina has been detached.
- The cause of the retinal detachment (RD).
- The amount of the retina that is involved.
- Whether the macula is involved.
If the RD does not involve the macula and is treated promptly, a good recovery with restoration of most of your vision is expected. It may take some weeks for vision to improve and glasses may be required permanently to aid vision.
If the macula has detached then the chances of treatment restoring your vision are much lower. Around 4 out of 10 people with macular detachment will recover useful vision. They tend to be patients in whom the macula was detached for a shorter period and they tend to be younger patients. Other patients may be left with some functional vision. However, for some, macular detachment will lead to severe visual impairment in the affected eye.
Having had RD in one eye increases the risk of it happening in the other eye. It can also occasionally recur in the first eye. For this reason you should be alert to any new symptoms and attend regular eye checks well into the future.
Dr Tim Kenny
Dr Mary Lowth
Dr Colin Tidy