Diabetic retinopathy, is retinopathy (damage to the retina) caused by complications of diabetes, which can eventually lead to blindness. The retina is the light-sensitive layer of cells at the back of the eye converting light into electrical signals. The signals are sent to the brain through the optic nerve and the brain interprets them to produce the images. To work effectively, the retina needs a constant supply of blood, which it receives through a network of tiny blood vessels. Over time, a continuously high blood sugar level can cause the blood vessels to become blocked or to leak. This damages the retina and stops it from working.
Blood vessels damaged from diabetic retinopathy can cause vision loss in two ways:
- Fragile, abnormal blood vessels can develop and leak blood into the center of the eye, blurring vision.
- Fluid can leak into the center of the macula (is an oval-shaped highly pigmented yellow spot near the center of the retina of the human eye), the part of the eye where sharp, straight-ahead vision occurs. The fluid makes the macula swell, blurring vision. This condition is called macular edema. It can occur at any stage of diabetic retinopathy, although it is more likely to occur as the disease progresses
Diabetic retinopathy often has no early warning signs.
Diabetic retinopathy is the result of micro-vascular retinal changes. Hyperglycemia-induced intramural pericyte death and thickening of the basement membrane lead to incompetence of the vascular walls. These damages change the formation of the blood-retinal barrier and also make the retinal blood vessels become more permeable. These bursting of blood vessels lead to development of abnormal blood vessels (neo-vascularization) on or adjacent to the optic nerve and vitreous.
The abnormal blood vessels formed from neo-vascularization (development of abnormal blood vessels) tend to break and bleed into the vitreous humor of the eye. Besides sudden vision loss, more permanent complications can include tractional retinal detachment (retinal detachment that which occurs due to pre-retinal membrane formation and scarring that pulls the retina from its attachment.) and neo-vascular glaucoma (is a severe form of secondary glaucoma characterized by proliferation of fibro-vascular tissue in the anterior chamber angle) .
Macular edema, which may cause vision loss more rapidly, may not have any warning signs for some time. In general, however, a person with macular edema is likely to have blurred vision, making it hard to do things like read or drive. In some cases, the vision will get better or worse during the day. About 10 percent of diabetic patients will get vision loss related with macular edema. The first time this happens, it may not be very severe. In most cases, it will leave just a few specks of blood, or spots, floating in a person's visual field, though the spots often go away after a few hours. These spots are often followed within a few days or weeks by a much greater leakage of blood, which blurs vision. In extreme cases, a person will only be able to tell light from dark in that eye. It may take the blood anywhere from a few days to months or even years to clear from the inside of the eye, and in some cases the blood will not clear. These types of large hemorrhages tend to happen more than once, often during sleep.
Diabetic retinopathy has four distinct stages.
- Mild Nonproliferative Retinopathy: At this earliest stage, micro-aneurysms occur. They are small areas of balloon-like swelling in the retina's tiny blood vessels.
- Moderate Nonproliferative Retinopathy: As the disease progresses, some blood vessels that nourish the retina are blocked. Non-proliferative diabetic retinopathy (NPDR) there are no symptoms, it is not visible to the naked eye and patients will have 20/20 vision.
- Severe Nonproliferative Retinopathy: Many more blood vessels are blocked, depriving several areas of the retina with their blood supply. These areas of the retina send signals to the body to grow new blood vessels for nourishment.
- Proliferative Retinopathy the signals sent by the retina for nourishment trigger the growth of new blood vessels. This condition is called proliferative retinopathy. These new blood vessels are abnormal and fragile. They grow along the retina and along the surface of the clear, vitreous gel that fills the inside of the eye.
As abnormal new blood vessels (neo-vascularisation) form at the back of the eye as a part of proliferative diabetic retinopathy (PDR). These can burst and bleed (vitreous hemorrhage) and blur vision, because the new blood vessels are weak.
The risk prone population includes all people with diabetes mellitus. The longer a person has diabetes, the higher the risk of developing some ocular problem.
People with Down's syndrome (people with three copies of chromosome 21) are lesser prone to acquire diabetic retinopathy. This protection appears to be due to the elevated levels ofendostatin, an anti-angiogenic protein, (derived from collagen XVIII, located on chromosome 21).
Several factors increase your risk of developing diabetic retinopathy.
1). the longer you have had diabetes, the greater your chance of developing retinopathy.
- About 90% of people with type 1 diabetes will have some degree of retinopathy after 10 years of having diabetic symptoms.
- For people with type 2 diabetes who do not need to take insulin, about 67% will have some degree of retinopathy after 10 years of having diabetic symptoms.
- For people with type 2 diabetes who need to take insulin, about 79% will have some degree of retinopathy after 10 years of having diabetic symptoms.
2). If you have diabetes and your blood glucose level (measured using the HbA1C test-- HbA1C is a form of haemoglobin and is the oxygen-carrying substance that is found in red blood cells and has glucose attached to it) is high, you have a higher risk of developing retinopathy.
3). If you have diabetes and high blood pressure, you have a higher risk of developing advanced retinopathy.
Early changes that are reversible and do not threaten central vision are sometimes termed simplex retinopathy or background retinopathy.
Diabetic retinopathy is the result of micro-vascular retinal changes. Hyperglycemia-induced intramural pericyte death and thickening of the basement membrane lead to incompetence of the vascular walls. These damages change the formation of the blood-retinal barrier and also make the retinal blood vessels become more permeable.
Small blood vessels – such as those in the eye – are especially vulnerable to poor blood sugar (blood glucose) control. An over accumulation of glucose and/or fructose damages the tiny blood vessels in the retina. During the initial stage, called non proliferative diabetic retinopathy (NPDR), most people do not notice any change in their vision.
Narrowing or blocked retinal blood vessels can be seen clearly and this is called retinal ischemia (lack of blood flow).
Macular edema may occur in which blood vessels leak contents into the macular region can happen at all stages of Non Proliferative Diabetic Retinopathy. The macular edema symptoms are blurring, darkening or distorted images with not the same between two eyes.
Diagnosis Treatment and Cure
The eye care professional will look at the retina for early signs of the disease, such as any changes in the blood vessels, leaking blood vessels, pale fatty deposits on the retina (exudates), damaged nerve tissue (neuropathy), retinal swelling or macular edema.
- If there is reduced vision, fluorescein angiography can be done to see the back of the eye.
- Optical Coherence Tomography can show areas of retinal thickening (fluid accumulation) of macular edema.
- Visual acuity test: This test uses an eye chart to measure how well a person sees at various distances (i.e., visual activity).
- Pupil dilation: The eye care professional places drops into the eye to widen the pupil. This allows him or her to see more of the retina and look for signs of diabetic retinopathy. After the examination, close-up vision may remain blurred for several hours.
- Ophthalmoscopy or fundus photography: Ophthalmoscopy is an examination of the retina in which the eye care professional: (1) looks through a slit lamp biomicroscope with a special magnifying lens that provides a narrow view of the retina, or (2) wearing a headset (indirect ophthalmoscope) with a bright light, looks through a special magnifying glass and gains a wide view of the retina. Hand-held ophthalmoscopy is insufficient to rule out significant and treatable diabetic retinopathy. Fundus photography generally recreate considerably larger areas of the fundus, and has the advantage of photo documentation for future reference, as well as availing the image to be examined by a specialist at another location and/or time. The only way to detect Non Proliferative Diabetic Retinopathy is by fundus photography, in which micro aneurysms (microscopic blood-filled bulges in the artery walls) can be seen.
- Fundus Fluorscein angiography (FFA): This is an imaging technique which relies on the circulation of Fluorescein dye to show staining, leakage, or non-perfusion of the retinal and choroidal vasculature.
- Optical coherence tomography (OCT): This is an optical imaging modality based upon interference, and analogous to ultrasound. It produces cross-sectional images of the retina (B-scans) which can be used to measure the thickness of the retina and to resolve its major layers, allowing the observation of swelling.
- Digital Retinal Screening Programs or Diabetic Retinopathy Screening Service (DRSS): This involves digital image capture and transmission of the images to a digital reading center for evaluation and treatment referral.
- Computer Vision Approach: It uses data analytics capabilities to automatically compare and analyse retina images of the patient. It can tell if the patient has Diabetic Retinopathy and also provides risk categorisation ranging from low to medium and high.
- Slit Lamp Biomicroscopy: Systematic programs for the early detection of diabetic retinopathy using slit-lamp bio-microscopy.
- Tonometry An instrument measures the pressure inside the eye. Numbing drops may be applied to your eye for this test.
Treatment for retinopathy will depend on the stage the condition has reached. If you have more advanced retinopathy, you may need to have laser surgery or injection therapy to prevent further damage to your eyes.
There are three major treatments for diabetic retinopathy; laser surgery, injection of corticosteroids or Anti-VEGF (a group of medicines which reduce new blood vessel growth or oedema (swelling)) into the eye, and vitrectomy (the surgical removal of the vitreous gel from the middle of the eye, in case of retinal detachment).
Preventive Care in Diabetic retinopathy involves following steps:
- Taking steps to prevent high blood pressure, such as giving up smoking and cutting down salt in your diet, can help reduce your risk of developing retinopathy.
- Avoiding tobacco use and correction of associated hypertension are important therapeutic measures in the management of diabetic retinopathy.
- Further preventive steps in diabetic retinopathy includes :
- Keep blood sugar within normal limits.
- Monitor blood pressure and keep it under good control.
- Maintain a healthy diet.
- Exercise regularly.
- Attending your annual screening appointment. Everyone with diabetes who is 12 years old or over should have their eyes examined once a year for signs of damage.
- informing your GP if you notice any changes to your vision (do not wait until your next screening appointment)
- taking your medication as prescribed
- losing weight (if you're overweight) and eating a healthy, balanced diet
Rehabilitation and Coping in Diabetic Retinopathy involves following measures:
Proliferative retinopathy can develop without symptoms. At this advanced stage, you are at high risk for vision loss.
Macular edema can develop without symptoms at any of the four stages of diabetic retinopathy.
You can develop both proliferative retinopathy and macular edema and still see fine. However, you are at high risk for vision loss.
- The best way of addressing diabetic retinopathy is to monitor it vigilantly and achieve euglycemia (The condition of having a normal concentration of glucose in the blood).
- Your eye care professional can tell if you have macular edema or any stage of diabetic retinopathy. Whether or not you have symptoms, early detection and timely treatment can prevent vision loss.
- If you have diabetic retinopathy, you may need an eye exam more often. People with proliferative retinopathy can reduce their risk of blindness by 95 percent with timely treatment and appropriate follow-up care.
- Other studies have shown that controlling elevated blood pressure and cholesterol can reduce the risk of vision loss. Controlling these will help your overall health as well as help protect your vision.