Also known as diabetic eye disease, this type of retinopathy is a severe complication of Diabetes mellitus (DM), affecting the retina´s blood vessels. This condition can be found in any diabetic patient, both type 1 and 2, and is the most common form of diabetic eye disease, being able of affecting both eyes.
If DM is mistreated or the diabetic patient becomes chronically ill, the chances of developing diabetic retinopathy increase with every day that passes. Almost 80% of people with DM for more than 20 years develop a form of diabetic retinopathy. The gravity of this problem is based on the fact that DM patients are 25 times more likely to become blind than people without it.
With proper treatment and monitoring, approximately 90% of cases could be reduced. Despite this, diabetic retinopathy is the leading cause of blindness, especially in people between 20 and 74 years old.
The risk factors include the duration of DM, lack of control of blood sugar levels (glycemia), high blood pressure, high cholesterol, nephropathy, proteinuria, tobacco consumption, etc. Also, pregnant women have a higher risk of developing DM and diabetic retinopathy.
How diabetic retinopathy is developed?
If your blood sugar levels remain too high for a long period of time, the small blood vessels located in your retina will get weaken and damaged until its blockage, not letting the nutrients pass and cutting off its blood supply. This process produces several changes in the retina, which at the same time produces more local complications, affecting the vision. If this damage continues, the affectation becomes major, possibly leading to blindness.
Some of the changes include the growth of new blood vessels to substitute the damaged ones. In this case, the new blood vessels will not develop in the right way, starting to weaken and leaking fluid (hemorrhages or exudates) into the retina. Due to the inflammatory process developing in the retina, scar tissue appears, increasing the pressure inside your eye, causing your retina to detach.
In this image are shown two kind of eyes. The one at the top is a normal and healthy eye, viewing its structures and especially the blood vessels, which enter and exit from the optic nerve. The eye at the bottom shows signs of diabetic retinopathy with hemorrhages and exudates due to the leaking of the blood vessels. This is one of the reasons that affects vision in diabetic patients.
Which are the diabetic retinopathy stages?
The first stage is the early diabetic retinopathy, medically called no proliferative diabetic retinopathy (NPDR). This is the more common form, in which the development of new blood vessels does not occur. Instead, the walls of the blood vessels located in your retina get weak and damaged.
In these small blood vessels, tiny bulges protrude forming microaneurysms, receiving the medical name of background retinopathy. This usually does not affect vision, however, in more serious cases (approximately 10%) with a larger number of microaneurysms, the affection of the vision is very probable.
Sometimes, blood or fluid can leak from this bulge into the retina. If the macula (the part of the eye that provides us with the central vision) gets affected by this, producing an increase in fluid pressure and swelling in the area (macular edema), blurry vision can appear, especially while reading. Medically, this is called diabetic maculopathy. Also in this stage, dilation of larger vessels and nerve fibers may appear. The severity of the retinopathy is related to the number of affected blood vessels of the retina.
The advanced diabetic retinopathy, which is the second stage, also known as the proliferative stage, is more severe. Its appearance is considered as an attempt to save the retina by growing new blood vessels.
In this type of diabetic retinopathy, new but abnormal blood vessels grow in the retina, leaking into the vitreous humor (the substance that fills the center of the eye and one of the elements that function as a lens). This growth stimulates scar tissue which may cause the retina to detach from its position. Increased eye pressure may appear, damaging the optic nerve, resulting in glaucoma.
What are the signs and symptoms of diabetic retinopathy?
This condition often has no early warning signs or visual symptoms. Macular edema, which is known for its rapid affectation of vision, may not show any symptomatology for some time. The patients that have an installed macular edema usually have blurry or cloudy vision, affecting things such as reading, driving or identifying a person´s face, and darkened or distorted images different in both eyes. During the day, vision may get better or worse.
The early diabetic retinopathy stage has none or little symptomatology. These patients usually have 20/20 vision and their visual signs are not visible with a simple physical exam. The only way to detect this stage is with a funduscopic (back of the eye) exam, in which the microaneurysms can be seen. Narrowed or blocked blood vessels, which causes retinal ischemia or lack of blood flow, can also be seen.
In the advanced diabetic retinopathy, the abnormal new blood vessels can burst and bleed, leaking into the vitreous humor, blurring the vision and causing eye pain. The first bleeds are not that severe. Usually, they leave a few spots floating (floaters) in the patient´s visual field, which often go away after a few hours.
A few days or weeks later, a much greater bleeding occurs (often during sleep), blurring the vision in a major way only being able to differentiate light from dark. The blood may clear in a varied period of time, which could take from days to months or even years. In some cases, the blood does not clear. With the use of the funduscopic exam, the physician will see cotton wool spots and flame or dot-blot hemorrhages.
Image that shows how a normal vision looks like.
Image that shows how the vision of a patient with advanced diabetic retinopathy looks like.
Image that shows how blurry vision can be in patients with macular edema.
How is diabetic retinopathy diagnosed?
Your ophthalmologist will do a complete examination of your eyes. Pupillary dilation is needed to have a better view of your eyes. To do so, the doctor will put a few drops in your eyes that will turn your vision blurry. This effect may last several hours until it disappears completely.
During the eye’s examination, the physician will search for abnormal growth of new blood vessels in your retina. Is important to discover if there are hemorrhages, swelling like macular edema, fatty deposits (exudates) or scar tissue. Also, the ophthalmologist is in the obligation to discover any complications produced by the diabetic retinopathy such as bleeding in the humor vitreous, retinal detachment or any abnormal signs in the eye´s optic nerve (neuropathy).
Your vision will be tested through a visual acuity test using an eye chart like the Snellen chart. The acuity is measured relating the patient´s perception with the size of the correspondent letters or symbols viewed on the chart. The result may be expressed as a fraction or a decimal number. The normal is to have a vision of 20/20 or 6/6.0 (which represents the same but in different measures) or 1.00 in decimals.
Your eyes pressure needs to be measured due to the possibility of glaucoma. The doctor will apply anesthetic drops to numb the eyes. After a few seconds, a specialized instrument is applied very gently in the front of the surface of the eyes. The physician will notice how much pressure appears indicated in the device. It is very important to remain calm and breathe normally. The procedure does not generate any pain. Normal eye pressure can go from 10 to 21 mmHg (scale in millimeters of mercury).
The other regular exam is the ophthalmoscopy or funduscopy, which is the examination of the retina using an ophthalmoscope or
Images that show photo documentation of two ophthalmoscopy exams. The one at the left shows a normal fundus. The one at the right show’s signs of diabetic retinopathy with macular edema, several hemorrhages (red spots) and exudates (yellow spots), humor vitreous opacity, and serious loss of vascularity.
An important ophthalmological exam is the fundus fluorescein angiography. This is an imaging technique in which the physician injects a special colorant into one of your arm´s veins, coloring your eyes´ blood vessels and taking pictures while the dye passes by. Your doctor will search for closed, broken or abnormal blood vessels.
The other specialized ophthalmological test is the optical coherence tomography (OCT). It is also an imaging technique which generates cross-sectional images of the retina, showing its thickness. This exam helps determine if the fluid has leaked into the tissue belonging to the retina. The technique is also used while treatment is being applied to monitor the developing results.
Diabetic retinopathy can be treated in different ways.
In early diabetic retinopathy stages, treatment is not that urgent. However, your ophthalmologist will closely pay attention to the state of your eyes, and depending on it, he will recommend you treatment or not. In this stage, prevention is key and usually, with good blood sugar levels the progression of diabetic retinopathy slows down.
In advanced diabetic retinopathy stages, the best treatment at the moment is surgery. Depending on the problems that your retina may present, the options are different.
In early stages of proliferative retinopathy with macular edema, photocoagulation or focal laser treatment is practiced. This is a laser technique used to stop or slow the leakage process that some blood vessels may present. This procedure is commonly done in your ophthalmologist´s office or clinic in just one session. The blurred vision produced by the macular edema may not completely disappear with the procedure, but this can reduce the possibility of having a worst evolution.
Another type of photocoagulation is the pan retinal one or scatter laser treatment. This procedure is used to reduce the abnormal blood vessels located in the portions of the retina far from the macula. It is also done in your ophthalmologist´s office or clinic in multiple sessions. It may be possible to present some loss of peripheral, color or night vision after the treatment.
These procedures are done only after applying a few anesthetic drops to achieve the eye´s numbness. The laser machine is placed in front of the patient´s correspondent eye while the physician uses a special lens. Is normal for the patient to see flashes of light while the laser is being applied. Blurry vision and headache are normal after the surgery.
Image that shows the result of panretinal photocoagulation treatment. The yellow spots represent the laser burns done to treat abnormal blood vessels. Notice that the laser treatment is done in the periphery, away from the macula.
In cases where there is a high amount of blood in the humor vitreous, a vitrectomy can be practiced. In this technique, a microscopic incision is done in your eye in order to remove the cloudy humor vitreous full of abnormal blood and replacing it with saline solution. The scar tissue that is damaging your retina is also removed.
Local or general anesthesia may be used. This procedure is done in a hospital or specialized surgery center. The patient may be able to return home or may be recommended to stay in the health center for one night. After the surgery, patients commonly use an eyepatch for a small period of time to protect the eye, along with medicated eye drops to prevent infections.
Your ophthalmologist may suggest injecting medication into your eye, specifically into the humor vitreous. This medication is known as vascular endothelial growth factor (VEGF) inhibitors and it works by blocking the signals sent by the body that promote the generation and growth of new blood vessels. This treatment may be applied as a stand-alone therapy or combined with photocoagulation.
The use of corticosteroids, injected or implanted into the eye, is also recommended by ophthalmologists to treat macular edema cases. The implants used are biodegradable, may last months, and are able to release a continuous dose of corticosteroids. This treatment may increase the risk of cataract and glaucoma, for this reason, patients submitted to this should be regularly monitored for increased eye pressure. This therapy may be used alone or combined with other medical or surgical therapies.
Even after surgery or medical treatment is applied, the diabetic retinopathy will remain as a lifelong condition. For this reason, is still possible to continue presenting damage to the retina and vision loss. Chronic patients may require multiple eye examinations and therapies to solve complications.
Several research studies and clinical trials using alternative therapies, such as light treatment, C-peptide therapy, and stem cells therapy are developing, but further investigation is needed.
If mistreated, what are the complications of diabetic retinopathy?
Severe vitreous hemorrhage can completely block the vision, which is not permanent unless there is a damage in the retina. As stated before, retinal detachment may happen due to the growth of scar tissue, which can pull the retina away from its location in the back of the eye. The abnormal blood flow happening in the retina increases the pressure inside the eye, leading to glaucoma. With time, this pressure affects the optic nerve. Chronic diabetic retinopathy, glaucoma or both can finally lead to the complete loss of vision.
How the diabetic patient can prevent diabetic retinopathy?
This condition is not always preventable, but with a few habit changes, vision loss can be prevented.
Include into your daily routine a healthy diet and regular physical activity. Do not stop taking your DM medication or insulin as prescribed. Keep monitoring your blood sugar levels depending on the severity of your case (once every 6 months, once every month, once every week, once a day or multiple times a day). Also, keep track of your blood pressure and cholesterol levels. Stop smoking and avoid alcohol abuse.
A very important point is to pay major attention to vision changes. If you experience sudden or progressive vision issues, consult your ophthalmologist right away. You have to remember that DM not always lead to vision loss, so taking an active role in its management can generate positive results in the prevention of complications.
- Harrison’s Principles of Internal Medicine (19th Ed).