What is a detached retina
A retinal detachment occurs when the retina is pulled away from its normal position in the back of the eye. The retina sends visual images to the brain through the optic nerve. When detachment occurs, vision is blurred. A detached retina is a very serious problem that almost always causes blindness unless it is treated.
The retina normally lies smoothly and firmly against the inside back wall of the eyeball and functions much like the film in the back of a camera. Millions of light-sensitive retinal cells receive optical images, instantly "develop" them, and send them on to the brain to be seen. If any part of the retina is lifted or pulled from its normal position, it is considered detached and will cause some vision loss.
The vitreous is the clear collagen gel that fills the back of the eye between the retina and the lens. As we get older the vitreous may pull away from its attachment to the retina at the back of the eye. Usually the vitreous separates from the retina without causing a problem. But sometimes the vitreous pulls hard enough to tear the retina in one or more places. Fluid may pass through the retinal tear and lift the retina off the back of the eye like wallpaper can peel off a wall.
Prevalence of detached retina
The risk of retinal detachment in otherwise normal eyes is around 5 in 100,000 per year. Detachment is more frequent in the middle-aged or elderly population with rates of around 20 in 100,000 per year. The lifetime risk in normal eyes is about 1 in 300.
Retinal detachment is more common in those with severe or extreme myopia (above 5-6 diopters), as their eyes are longer and the retina is stretched thin. The lifetime risk increases to 1 in 20. Myopia is associated with 67% of retinal detachment cases. Patients suffering from a detachment related to myopia tend to be younger than non-myopic detachment patients.
Retinal detachment can occur more frequently after surgery for cataracts. The estimate of risk of retinal detachment after cataract surgery is 5 to 16 per 1000 cataract operations. The risk may be much higher in those who are highly myopic, with a frequency of 7% reportin one study. Young age at cataract removal further increased risk in this study.
Tractional retinal detachments can also occur in patients with proliferative diabetic retinopathy or those with proliferative retinopathy of sickle cell disease. In proliferative retinopathy, abnormal blood vessels (neovascularization) grow within the retina and extend into the vitreous. In advanced disease, the vessels can pull the retina away from the back wall of the eye causing a traction retinal detachment.
Although retinal detachment usually occurs in one eye, there is a 15% chance of developing it in the other eye, and this risk increases to 25-30% in patients who had cataracts extracted from both eyes.
What are the symptoms
A retinal detachment is commonly preceded by a posterior vitreous detachment which gives rise to these symptoms:
- flashes of light (photopsia) - very brief in the extreme temporal (outside away from the nose) part of vision
- a sudden dramatic increase in the number of floaters
- a ring of floaters or hairs just to the temporal side of the central vision
- a slight feeling of heaviness in the eye
Although most posterior vitreous detachments do not progress to retinal detachments, those that do produce the following symptoms:
- a dense shadow that starts in the peripheral vision and slowly progresses towards the central vision
- the impression that a veil or curtain was drawn over the field of vision
- straight lines (scale, edge of the wall, road, etc.) that suddenly appear curved (positive Amsler grid test)
- central visual loss
What causes a detached retina
Thickening of the vitreous humor happens naturally during aging. As volume of the fluid contracts, it can pull the retina along with it, making a small hole in the retina. When the retina tears, this allows vitreous fluid to leak behind the retina and further lift it up.
Retinal detachment can occur at any age, but it is more common in midlife and later.
There are some known risk factors for retinal detachment. There are also many activities which at one time or another have been forbidden to those at risk of retinal detachment, with varying degrees of evidence supporting the restrictions.
Cataract surgery is a major cause, and can result in detachment even a long time after the operation. The risk is increased if there are complications during cataract surgery, but remains even in apparently uncomplicated surgery. The increasing rates of cataract surgery, and decreasing age at cataract surgery, will inevitably lead to an increased incidence of retinal detachment.
Trauma is a less frequent cause. Activities which cause direct trauma to the eye (boxing, kick-boxing, karate and others) can cause a particular type of retinal tear called a retinal dialysis. This type of tear can be detected and treated before it develops into a retinal detachment. For this reason governing bodies in some of these sports require regular ophthalmic examination.
Individuals prone to retinal detachment due to a high level of myopia are encouraged to avoid activities where there is a risk of shock to the head or eyes, although without direct trauma to the eye the evidence base for this may not be convincing. Some doctors recommend avoiding activities that increase pressure in the eye, including diving, skydiving, again with little supporting evidence.
Activities that involve sudden acceleration or deceleration also increase eye pressure and are discouraged by some doctors. These include bungee jumping, but may also include rollercoaster rides.
How is a detached retina diagnosed
Retinal detachment can not be seen unless the eye is dilated. Diagnosis can be done by examining the retina via:
- Ophthalmoscopy (shining light in to visualize the retina)
- Slit Lamp Examination (shining light in to visualize the retina)
- Fluorescein Angiography (dye-aided photography of the retina)
Retinal examination is done in conjunction with standard tests of vision ability and eye function:
- Refraction Test
- Color Perception
- Pupillary Reflex Response
How can a detached retina be treated
Retinal tears will usually need to be treated with laser surgery or cryotherapy (freezing), to seal the retina to the back wall of the eye again. These treatments cause little or no discomfort and may be performed in your ophthalmologist's office. This treatment will usually prevent progression to a retinal detachment. Occasionally retinal tears are watched without treatment.
Retinal detachments may require surgery to return the retina to its proper position in the back of the eye. There are several ways to fix a detached retina. The decision of which type of surgery and anesthesia (local or general) to use depends upon the characteristics of the retinal detachment. In each of the following methods, your ophthalmologist will locate any retinal tears and use laser surgery or cryotherapy (freezing) around them to seal the tear.
Pneumatic retinopexy describes the injection of a gas bubble into the vitreous space inside the eye enabling the gas bubble to push the retinal tear back against the wall of the eye and close the tear. Laser or cryo-surgery is used to secure the retina to the eye wall around the retinal tear. Your ophthalmologist will ask you to maintain a certain head position for several days. The gas bubble will gradually disappear. Sometimes this procedure can be done in the ophthalmologist's office.
A scleral buckle or flexible band is placed around the equator of the eye to counterbalance any force pulling the retina out of place. Often the ophthalmologist will drain the fluid from under the detached retina allowing the retina to return back to its normal position against the back wall of the eye. This procedure is performed in the operating room, usually on an outpatient basis.
Vitrectomy may be necessary to remove any vitreous gel which is pulling on the retina. This may also be necessary if the vitreous is to be replaced with a gas bubble. Your body's own fluids will gradually replace this gas bubble, but the vitreous gel does not return. Sometimes a vitrectomy may be combined with a scleral buckle.
You can expect some discomfort after retinal surgery. Your ophthalmologist will prescribe any necessary medications for you and advise you when to resume normal activity. You will need to wear an eye patch for a short time. If a gas bubble was placed in the eye, your ophthalmologist may recommend that you keep your head in special positions for a time. A change of glasses may be necessary after the retina has been reattached.
What are the risks of surgery?
Any surgery has risks; however, an untreated retinal detachment will usually result in permanent severe vision loss or blindness. Some of these surgical risks include infection; bleeding; high pressure inside the eye; or cataract. Most retinal detachment surgery is successful, although a second operation is sometimes needed. If the retina cannot be reattached, the eye will continue to lose sight and ultimately become blind.
Will my eyesight improve
Vision may take many months to improve and in some cases may never fully return. Unfortunately, some patients, particularly those with chronic retinal detachment, do not recover any vision. The more severe the detachment, and the longer it has been present, the less vision may be expected to return. For this reason, it is very important to see your ophthalmologist at the first sign of trouble.
If the macula has not detached, prognosis for return of normal vision remains good.
For vitrectomy the hole is successfully plugged in nine out of ten cases.
Afterward about half of patients can make out two lines further down the standard eye chart.
Reattachment of the retina is also effective in ninety percent of patients.
The remaining ten percent will need a repeat procedure, which is usually then successful.