What is Diabetic retinopathy, what causes diabetic retinopathy, what are the stages of Diabetic retinopathy, what is the treatment for diabetic retinopathy, what is its pathophysiology?
All these questions and more will be answered in this write-up.
So what is Diabetic Retinopathy?
Diabetic retinopathy can be defined as damage to the retina of the eyes caused by complications arising from diabetes. The nature of the damage to the eyes may be the swelling and leaking of blood into the aqueous fluid of the eyes or the growth of abnormal new blood vessels on the surface of the retina.
Either way this condition can lead to blindness. In fact it is estimated that the condition afflicts up to 80 percent of people who have had diabetes for 10 years or more and each year in the United States, diabetic retinopathy is responsible for 12 percent of all new cases of blindness.
Diabetic Retinopathy progresses through various stages and as with most conditions the earlier it is diagnosed the better the prognosis for recovery.
The first stage called None-Proliferative Diabetic Retinopathy (NPDR) may not be obvious to the sufferer. At this stage it is not visible to the naked eye, there are no symptoms and patients will have normal vision. In fact the only way to detect Diabetic Retinopathy or DR at this stage is to undergo an ophthalmoscope or fundus photography – a type of photography in which microscopic blood-bulges in the artery walls otherwise known as micro aneurysms can be seen.
Where there is reduced vision, fluorescein angiography (FFA) to see the back of the eyes can be done. This will enable the examiner to clearly see whether there is narrowing or blocked retinal blood vessels, a condition known as retinal ischemia (lack of blood flow).
Where blood vessels leak into the macular region of the eye, this is known as Macular oedema and it can occur at all stages of NPDR. Symptoms of this condition include darkening, blurring or distorted images although the degree of such usually varies between the two eyes.
It is stated that 10 percent of diabetic patients will lose their vision as a direct result of macular oedema. Optical Coherence Tomography (OCT) can help show areas of the retina most severely affected by the condition.
At stage 2, moderate none-proliferative Retinopathy-the excessive accumulation of blood glucose and/or fructose damage and block the tiny blood vessels in the retina that nourish it. After this comes severe none proliferative Retinopathy where many blood vessels are blocked. As a result many areas of the retina is blocked from their blood supply. These then send signals to the body requiring it to grow new blood vessels for nourishment. In response the body begins to do so.
However due to a lack of oxygen in the retina, the blood vessels that grow are abnormal and are known as neovascularization form.They grow at the back of the eye, along the retina and in the vitreous humour (These new blood vessels are however weak. As such they can burst and leak into the vitreous humour (vitreous haemorrhage) causing blurred vision, destroying the retina and ultimately causing blindness. This is known as Proliferative diabetic retinopathy-PDR.
The first occurrence of this may not be severe and specks of blood left in a person’s visual field often go away after a few hours. Following experiences a few days or weeks after however, may lead to a greater leakage of blood which causes blurred vision. And the clearing of this type of leakage from the eyes can take anywhere from between a few days to a few years to never. These type of haemorrhages tend to happen during sleep.
So who is at risk of this condition?-basically anyone with diabetes, whether Type 1 or 2. Moreover the longer a person has diabetes, the greater the risk of him coming down with diabetic retinopathy.
In America between 40 to 45 percent of people diagnosed with diabetes are at some stage of the disease. As such it is recommended that everyone with diabetes should do a comprehensive dilated eye exam at least once a year. Spotting it on time will enable treatment essential to arresting its progress.
Furthermore, it has been established that diabetic pregnant women are at an increased risk for this condition. As such, the recommendation is that every pregnant woman with diabetes should undergo a comprehensive dilated eye exam each trimester to guard against loss of vision.
So then if you are diabetic or have an interest in prevention, you may want to know what you or a person at risk can do to protect his vision. Well first things first-take a comprehensive dilated eye exam at least once a year. Don’t think because your vision is 20/20 now, you don’t need it. Remember that proliferative Retinopathy can occur without any outward symptoms and it is best treated in its first stage when there are no overt symptoms or manifestation of impaired vision. As a matter of fact, studies show that risk of blindness due to proliferative Retinopathy can be reduced by 95% where timely intervention and appropriate care is applied.
This comprehensive test will include the Visual Acuity test- an eye chart test, to measure vision accuracy at various distances; the Dilated eye exam- where drops are placed in your eyes to dilate or widen the pupils, thereby enabling the examiner to see more of the inside of the eyes to check for signs of damage; Tonometry, where an instrument is used to measure the pressure inside the eyes; Slit-lamp Bio microscopy Retinal Screening programs- a system that uses slit lamp bio microscopy in the detection of diabetic retinopathy.
Early signs of the disease which can be spotted during this examination are; leaking blood vessels, retinal swelling (macular oedema); damaged nerve tissue, pale fatty deposits on the retina, this being a sign of leaking blood vessels and any changes to the blood vessels. These early interventions will enable your doctor determine the best course of action to take to arrest the disease
Again, it has been found by the Diabetes Control and Complications Trial (DCCT) that better control of blood sugar levels, high blood pressure and cholesterol impedes the development and progression of retinopathy. As a result, the need for sight saving laser surgery is reduced.
That said, barring macular oedema, generally, no treatment is necessary during the first three stages of diabetic retinopathy. Nevertheless where treatment is needed, Scatter Laser surgery may be employed for diabetic retinopathy. Two or more sessions are normally required to complete this treatment and the side effects may include some loss of side vision and/or reduction in colour and night vision.
Where there is bleeding of the new blood vessels and such bleeding severe, a surgical operation known as a vitrectomy may be carried out to remove the blood from the eyes. Both of these treatments are quite effective.
In the case of Macular oedema, laser surgery is also employed. Called Focal laser treatment, several small laser burns are placed by the doctor in the area of retinal leakage surrounding the macula. These both slow the leakage of and reduce the amount of fluid in the retina. Usually completed in one session, the treatment has been found to reduce the risk of vision loss by 50 percent.
In treating macular oedema, the prompt use of the drug Lucentis, Avastin or Aylea with or without laser treatment, is also found to result in better vision than laser treatment alone or steroid injections. When injected into the eye, it reduces fluid leakage and interferes with the growth of new blood vessels in the retina.
Today ongoing research supported by the National Eye Institute (NEI), United States, is looking into drugs that may stop the retina from sending signals to the body to grow new blood vessels and so prevent diabetic retinopathy.