Retinal detachment

The purpose of this article is to explain what a retinal detachment is in addition to outlining its causes, symptoms, common risk factors and treatment.

What is a retinal detachment?

A retinal detachment is a serious and potentially blinding condition that has to be treated urgently. The eye is a hollow, ball-shaped organ that is filled with a watery jelly called vitreous. When we are children the vitreous has a firm consistency similar to dessert jelly. As we get older, this jelly becomes softer. This “mushy” jelly can swirl around inside the eye and exert pulling forces where it is attached to the retina. It is common in many people for the vitreous jelly to eventually disintegrate and separate from the retina and usually this happens without complication. This is called a “posterior vitreous detachment” (PVD) and is usually not a problematic condition.

The retina is the innermost lining of the wall of the eyeball and it is a very important tissue. The retina converts light energy into nerve impulses that go to the brain and allow us to see. It is a thin lining that is only one quarter of a millimetre in thickness and is very fragile. Occasionally when the aforementioned PVD occurs it can cause a tear in the retina that can lead to a retinal detachment. The reason a tear can cause a retinal detachment is that water (within the vitreous jelly) can leak in underneath the retina and lift it off the wall of the eyeball causing a retinal detachment. Some eye doctors compare this process to dampness getting underneath wallpaper (akin to the retina) and the wallpaper peeling of the plasterwork, this is a good analogy. If the retina is detached from the wall of the eyeball then it stops working and stops converting light into nerve energy and this is why the eye goes blind.

 

Flashes and Floaters

As explained above, the first step of a retinal detachment is the disintegration and separation of the vitreous jelly called a PVD. The symptoms of this process are “flashes and floaters”. Flashes occur when the retina is being “tugged” by the disintegrating jelly. People often describe this symptom as being like a camera flash or sometimes they initially think someone is shining a torch towards them. Sometimes patients experience a fleeting arc of light in their peripheral vision. The symptom of ‘floaters’ are usually due to pieces of the fabric of the vitreous jelly floating around in the eye and casting shadows on the retina. Occasionally if there is a small bleed in the eye patients can also complain of floaters. Patients often describe floaters as being like cobwebs floating in their vision or like tadpoles swimming around in the vision, sometimes they think there is a hair hanging down over the eye that can’t be brushed away. It is important to realise that a PVD is a very common condition that only rarely leads to retinal tears and detachments. However, it is important to have your pupils dilated and your eyes examined by an eye doctor if you notice these symptoms.

If a patient is unlucky and the PVD pulls on the retina causing a tear, a retinal detachment can occur. The symptoms of a retinal tear can be similar to a PVD i.e. flashes and floaters, but these are often more severe and pronounced. Sometimes the retinal tear can bleed into the eye making the central vision blurry or causing floaters that are very large and alarming.

If the torn retina starts to detach the patient will notice a shadow coming across the vision. Most retinal detachments start in the upper retina which is the part of the eye that sees downwards so these people notice a shadow coming up from the bottom of their vision but shadows can also come from the sides or the top of the vision. If you notice this symptom you really need to get examined by an eye doctor urgently.

 

What are the risk factors for retinal detachment?

Short sightedness (myopia) is probably the biggest risk factor for retinal detachment. It is not known exactly why but it probably has something to do with short-sighted eyes being larger than normal and therefore the retina may be stretched and thin. Myopia of more that minus 3 dioptres causes a 10-fold increase in the risk of retinal detachment and more than half of all retinal detachments occur in short-sighted eyes.

Previous cataract surgery is also an important risk factor. Approximately one in 200 people who have cataract surgery will suffer a retinal detachment and 20% of all retinal detachments occur in eyes that have already undergone cataract surgery.

Prior personal history of retinal detachment is also important; one in ten people who suffer a retinal detachment go on to have a detachment of the retina in the other eye. So if you have had a retinal detachment you should be especially vigilant for symptoms in your second eye.

Other risk factors include: advancing age, trauma to the eye or head and family history of retinal detachment.

 

What is the treatment for retinal detachment?

The treatment for retinal detachment is surgery and the surgery is, generally-speaking, very successful. There are two main operations used and these are called Scleral Buckle and Vitrectomy, sometimes a combination of both operations is used. There are various advantages and drawbacks to each type of procedure and the best one to use depends on lots of different variables that the surgeon will take into account before or even during the operation.

 

Scleral Buckle

This is when the retinal surgeon stiches a piece of plastic onto the outside of the eye that causes an indentation of the wall of the eye. This indentation brings the outside wall of the eye inwards so that it touches or comes close to the detached retina where the tear is. This stops or reduces the flow of water through the tear and under the retina and also tends to relax any inward pulling forces that are caused by the vitreous jelly or by scar tissue. Sometimes the plastic goes all the way around the eye like a belt-buckle or otherwise a smaller piece of plastic is used over a segment of the eye. During the operation the retinal tear is “sealed” to make it watertight. This is achieved by either heating it with laser energy or freezing it with cryotherapy both causing helpful scar tissue that “glues” the torn retina to the outer wall of the eye. Sometimes, if there is a lot of fluid under the retina, a small drainage hole can be made through the wall of the eye and the fluid can be drained but often this is not necessary, as the body tends to absorb this fluid naturally once the retinal tear is closed off adequately.

 

Vitrectomy

This is surgery that is done mainly inside the eyeball through tiny “keyhole” ports that are placed through the wall of the eyeball by the retinal surgeon. In this operation, there are generally three ports, one is for the fibre-optic light-pipe that allows the surgeon to see inside, the second is for the vitrectomy instrument that cuts away and aspirates the vitreous jelly and the third port is where the all-important infusion line is placed. The infusion line pumps a salty liquid into the eye and keeps it inflated while the vitreous jelly is removed from the inside.

The patient has an anaesthetic, usually the patient is asleep but nowdays, it is becoming more common for the procedure to be done under local anaesthetic. The patient lies down and the surgeon usually sits at the top of the table where the patient’s head is. The ports are inserted and the vitreous jelly is removed from inside the eye. This allows the retina to “fall” back into place against the outside wall of the eye. Fluid that is underneath the retina is aspirated away through the tear and the retina goes flat against the wall of the eye. When the retina is back in place cryo or laser therapy can be applied around the tear, which sticks the tear down and prevents fluid from getting back under the retina. Usually a special type of “bandage” consisting of either gas or oil is placed in the eye at the end of the operation. This keeps fluid away from the tear and allows the retina some time to heal. If a gas bandage is used the gas will slowly disappear over a number of weeks as it is absorbed naturally by the body. However, if oil is used it will have to be removed after period of time with a second operation, usually oil is not removed for at least three months after the first surgery.

An important part of successful retinal detachment surgery depends on the patient posturing correctly following surgery. Often, the surgeon will ask the patient to lie with the head at a certain angle. This posturing is designed to keep the tear covered with the internal bandage while the retina heals. This is most important with a gas bandage and the idea is to get the gas bubble to float up against the tear so that the tear stays dry while it heals. The patient usually needs to posture for approximately two weeks after surgery and some patients find this to be quite a challenge.

 

Prognosis and conclusion

For the most common types of retinal detachment the main factor that determines how well a patient will do depends on how quickly they seek help after the detachment starts to occur. Retinal detachment surgery has improved hugely over the last twenty years and is generally speaking very successful nowadays.

Between 80 and 90 percent of retinal detachments can be successfully “fixed” with one operation. This means that the surgeon is usually able to re-attach the retina with one operation. Unfortunately, the level of vision that a patient maintains can be quite variable as the retina can be damaged and bruised on account of being detached. If, at the time of surgery, the area of detached retina is small and the central part of the retina (the macula) is still attached the prognosis is good and most people maintain a level of vision in the eye that is good enough to read or drive a car. However, if the central part or macula is detached before the operation and the vision is already reduced then the level of vision a patient gets back can be very variable with some people regaining good vision but others not. Overall, approximately 50% of people who have a retinal detachment involving the central retina regain vision that is good enough to read (6/15 visual acuity) however there are many different variables at work in these cases and the most important thing from a patient’s perspective is to seek help as soon as any symptoms are noticed.