Diabetes is a common condition which may occur at any time in life. There are two types of Diabetes, namely Type 1 and Type 2.
Both types of diabetes can potentially cause blindness. Unfortunately, at first the damage to the eye may occur without symptoms and hence patients may not be aware that their eyes have been damaged.
As a result ALL diabetics need to have their eyes regularly checked by an ophthalmologist.
Type 1 diabetes will often occur at a young age and is caused by a failure of the pancreas to make insulin. Insulin is a chemical substance naturally produced by the body which controls storage of dietary sugars. Failure to produce insulin cause high levels of circulating blood sugar.
Type 2 diabetes is usually seen in adults and is associated by resistance of the body to the effects of insulin. In Type 2 diabetes, insulin is produced but the body no longer responds to its action.
RETINA: A layer of special light-sensitive tissue at the back of the eye that sends nerve impulses up the optic nerve to the brain.
This process is responsible for vision. If the retina becomes damaged by disease, then the quality of vision is affected or even lost.
In people with diabetes, tiny blood vessels in the retina may become diseased and damaged due to the effects of diabetes. Diabetes can cause the blood vessels to swell and leak blood or fluid around the retina. As they heal, scar tissue forms on the retina. The retina can be damaged so badly that it functions less effectively and vision is impaired.
This disease process is called diabetic retinopathy.
The process is usually slow, over months or years. The longer the person has diabetes, the greater the risk of diabetic retinopathy.
THE MACULA: this is the area of retina that provides the sharpest vision.
Leaking blood or fluid can cause the macula to swell, which is called macula oedema. This causes blurred vision and is a common result of diabetic retinopathy. Blood vessels can grow and eventually bleed. This can cause a less common but more damaging form of retinopathy that can lead to blindness.
All people with diabetes are at risk of developing retinopathy to some degree, whether or not they are insulin dependent. Of every 10 people who have had diabetes for 15 years, about 8 have some damage to their retina.
If left untreated the patient risks serious damage to vision that can lead to blindness. However, due to modern surgical and medical treatments, only a small number of people with diabetic retinopathy have serious damage to their vision. Early diagnosis and treatment is the best way to prevent loss of vision. If the retina becomes damaged so badly that sight is affected, no surgical or medical treatment can restore the lost vision.
Diabetic retinopathy does not cause pain, and the person may not notice any changes to vision until the disease has caused severe damage to the retina. A person with diabetes must have an eye examination every year.
The two types of retinopathy are non-proliferative (or background) retinopathy and proliferative retinopathy.
This is the early stage of the disease. Typical signs include tiny areas of bleeding or leaking from blood vessels. Most people do not notice any changes in vision at this stage hence the need for regular examinations by your ophthalmologist.
In some early cases, macular oedema may develop, which requires immediate treatment. Early treatment is better than waiting for signs or symptoms to develop even though the person may not be aware of problems.
As long as the macula is not threatened, treatment at this stage may not be needed, only careful observation. Patients with this early form of the disease should be careful to control their diabetes, blood pressure and cholesterol very carefully to limit further damage.
As the disease worsens, new blood vessels grow or “proliferate” in an attempt to provide a better blood supply to the retina. These blood vessels are weak and bleed easily into the vitreous of the eye and vision becomes blurred. The blood is slowly absorbed by the body therefore impaired vision can take weeks or months to improve, depending on the size of the bleed.
Scar tissue that forms on the retina can pull the retina out of position and in severe cases may cause the retina to detach from the wall of the eye causing loss of vision. Macular oedema is common at this stage. These processes can lead to poor vision and sometimes blindness.
People with diabetes have a higher risk of developing other eye diseases like glaucoma and cataract. Risk of developing glaucoma or a cataract in either eye is twice that of a non-diabetic person.
Diabetic retinopathy cannot be fully prevented, but the risk of impaired vision or blindness can be greatly reduced by good management of diabetes. Blood pressure, elevated cholesterol and smoking are additional risk factors.
Your ophthalmologist needs to know your complete medical history to plan the best treatment.
Your ophthalmologist will need to know about any:
SMOKING: Patients are advised not to smoke, as this accelerates the damage that diabetes causes to the retina and other vital parts of the body.
Your ophthalmologist will give you a vision test and a full eye examination.
Drops are put in the eyes to enlarge the pupils. An ophthalmoscope with a bright light is used to examine the retina. Fluid pressure inside the eye is checked, and photographs of the retina may be taken with a special camera.
A test called fluorescein angiography may be needed in some cases. A special yellow dye is injected into a vein in the arm or hand. This dye enters the bloodstream, and as it passes through blood vessels in the retina, photos are taken to detect whether dye has leaked from the tiny retinal blood vessels. The most common side effects of fluorescein angiography include brief nausea and a mild allergic The yellow dye does not stain the eye, but urine will be bright yellow for a day or two afterwards.
If your ophthalmologist finds signs of advanced retinopathy or macular oedema, laser treatment may be recommended.
The two surgical treatments for diabetic retinopathy are laser treatment and vitrectomy.
It is important to realise that neither laser treatment nor surgery will cure diabetic retinopathy but can be effective in slowing or preventing further vision loss.
IT IS IMPORTANT TO REALISE THAT TREATMENT AT THIS STAGE WILL BE PERFORMED FOR TWO MAIN REASONS:
Laser treatment (photocoagulation)
Laser treatment in diabetes is the most important modality used. Laser treatment aims to either:
Your doctor will usually instil drops to enlarge the pupil to give a better view of the retina. A special lens is held to the eye to stop the eye blinking and to help the ophthalmologist see the retina.
The laser (a high-energy, pinpoint light beam) is focused on each area to be treated. The ophthalmologist uses the laser beam to seal leaking blood vessels and to shrink abnormal vessels.
Macular oedema (fluid leakage in the reading part of the retina) is treated by using the laser to seal leaking blood vessels near the macula. This is usually completed in one session, but more sessions may be needed. This shorter laser treatment for sealing blood vessels is usually not painful. However the multiple, more complicated and longer treatments to shrink blood vessels in proliferative disease can cause discomfort. Local anaesthetic and pain-relieving medication can be given at the time of treatment. Several sessions of laser treatment may be needed. Each treatment session takes about 15 to 30 minutes.
When a lot of blood has leaked into the eye, and vision does not clear or the retina has detached, a vitrectomy may be needed. Many patients will require laser treatment of retinal blood vessels before a vitrectomy is performed.
Whilst vitrectomy surgery is always performed in the operating theatre, some types of laser treatment will be done in day surgery or in the ophthalmologists’ rooms.
Vitrectomy Surgery
The ophthalmologist uses an operating microscope to see the retina and other structures inside the eye. Tiny cuts are made into the sclera (white of the eye). Special instruments and a bright fibre optic light are then inserted into the vitreous cavity. Vitreous contaminated with blood is removed with a hand-held cutting device and replaced with a clear salt solution similar to the liquid removed from the eye. This salt solution is absorbed over time and slowly replaced by fluid produced by the eye.
In some cases, depending on the surgeon’s techniques, a special synthetic gas or silicone oil may be applied inside the eye. The gas is slowly absorbed and replaced by the eye’s natural fluid. If silicone oil is required, it cannot be absorbed by the body and may have to be removed during second operation at a later time. The surgeon may remove retinal scar tissue if any is present and causing a problem. Long-term outcome is generally good. This outcome also depends on whether the retinopathy.
The procedure usually takes between 1 and 2 hours. You may have to stay overnight. If cataract is present, the surgeon may remove the lens during the vitrectomy. This can also be helpful during difficult cases where scar tissue takes a long time to remove. During the vitrectomy or at a later procedure, the lens can be replaced with an artificial lens implant. Cataract with intraocular lens implant may also be necessary to monitor less severe forms of retinopathy and allow effective laser treatment.
Recovery of vision after laser or vitrectomy surgery depends on many factors, which are different in each patient. The main factor which will determine recovery of vision in diabetes, is the amount of blood vessel damage from the disease process. This is why good control of the actual disease is far more important than the surgery or the laser.
Your doctor will discuss your specific expected visual recovery, and will advise you about when it is safe to start work or driving, if appropriate.
