In diabetic retinopathy, the blood vessels of the retina become abnormal and cause the problems that diabetic patients have with their eyesight. In a normal eye, the blood vessels in the retina do not leak. In patients with diabetes, the retinal blood vessels can develop tiny leaks. These leaks cause fluid or blood to seep into the retina. The retina then becomes wet and swollen and cannot work properly. The form of diabetic retinopathy caused by leakage of the retinal blood vessels is called non-proliferative diabetic retinopathy (NPDR).
Another problem with the retinal blood vessels in diabetes is that they can close. The retinal tissue, which depends on those vessels for nutrition, will no longer work properly. The areas of the retina in which the blood vessels have closed then foster the growth of abnormal new blood vessels that can be very bad for the eye, as they can cause bleeding and scar tissue that may result in a total loss of vision. This is called proliferative diabetic retinopathy (PDR).
Early Diagnosis Of Nonproliferative Diabetic Retinopathy
It is very important for all patients with diabetes to have an annual eye exam. Depending of the severity of one’s eye disease, one may need to be examined as often as ever every 1-6 months. It is also important that patients be aware of what they are seeing with each eye. If a patient can detect a problem with vision very early, the chance of saving eyesight with laser surgery or antiVEGF therapy is much greater. For this reason, everyone should test the vision in each eye, separately, each day.
One way to test vision in order to detect even small changes when they first appear is to use the Amsler grid. Follow these instructions:
- Wear your reading glasses and hold the Amsler grid at a normal reading distance.
- Cover one eye.
- Look at the center dot and keep looking at it at all times.
- While looking directly at the center, be sure that all the lines are straight and all the small squares are the same size.
- If you should notice any changes on the grid such as distortion, blur, discoloration, or other abnormality, and it stays that way for a few days, call and see your eye doctor right away.
- Be sure to test the other eye in the same manner.
Laser Surgery For Diabetic Retinopathy
The laser is often used to stop abnormal retinal blood vessels from leaking fluid into the retina. Vision does not usually improve with a laser, but laser treatments can frequently stop further loss of vision. When the swelling of the retina or amount of exudate in the macula has reached a critical stage, laser treatments should be performed so that vision does not deteriorate further. Your own doctor can help you evaluate your chances with laser surgery and discuss the options with you.
Even when laser surgery has successfully sealed the leaking vessels, new areas of leakage frequently appear later, causing more swelling and more loss of vision. The patient who is treated with laser should continue to check the vision in each eye daily and tell the doctor immediately if there are new changes, such as a return of distortion or blurriness. Vision does not usually improve with laser surgery, but if NPDR is discovered early enough, laser surgery may stop further loss.
Anti VEGF Therapy For Diabetic Macular Edema
VEGF (Vascular endotheilial growth factor) is the chemical in the retina that causes blood vessels to leak resulting in diabetic macular edema. Recent studies have shown that anti-VEGF injections of either Avastin or Lucentis into the eye are very effective in treating diabetic macular edema. Thus, either Anti-VEGF alone or in combination with laser treatment appears to be the better treatment for macular edema. Studies are ongoing.
Proliferative Diabetic Retinopathy
In Proliferative Diabetic Retinopathy, retinal blood vessels close off, and large areas of retina lose their source of nutrition. The retina responds by developing new blood vessels that are abnormal, called neovascularization. The development of neovascularization is dangerous to the eye. Neovascularization does not nourish the retina properly, and it may cause bleeding into the vitreous cavity and the growth of scar tissue on the retina. Some patients will develop a tractional retinal detachment, leading to severe vision loss or blindness.
Neovascularization can also occur on the iris, the colored part of the eye, rather than just on the retina. When neovascularization grows on the iris (called rubeosis), it may close off normal flow of fluid out of the eye and cause the pressure in the eye to rise to dangerously high levels. The high pressure (called neovascular glaucoma) can cause permanent changes, resulting in visual loss, pain, or even loss of the eye.
It is very important to understand that the closing of retinal blood vessels and the development and growth of neovascularization may occur without any noticeable change of vision. So, it may be impossible for the person with diabetes and early PDR to know that such changes are occurring. For this reason, it is essential that every person with diabetes be examined regularly by a specialist who is familiar with diagnosing diabetic retinopathy. Such examinations should occur regularly–at least every six to twelve months–for the lifetime of the person with diabetes. The earlier neovascularization is discovered, the better the chance the vision will be saved. The later the neovascularization is discovered, the greater the chance for blindness.
When one develops proliferative diabetic retinopathy, pan retinal photocoagulation (PRP) is often recommended and performed. The idea is to use the laser to destroy all of the dead areas of retina where the blood vessels have been closed. When these areas are treated with the laser, the retina stops manufacturing new blood vessels, and those that are already present tend to decrease or disappear.
Pan retinal laser photocoagulation does not improve vision. However, it is the best possible means of holding vision stable to prevent further loss. After laser surgery, patients may still have reduced vision or may continue to lose more vision. But if pan retinal laser photocoagulation is indicated, the chances are that it will prevent severe loss of vision.
Because PRP is placed in the peripheral retina, peripheral (side) vision will be diminished to some extent. These side areas are sacrificed in order to save as much of the central vision as possible and to save the eye itself. Night vision will also be diminished. After laser, blurred vision is very common. Usually, this blur goes away, but in a small number of patients, some blur will continue forever.
Some patients with proliferative diabetic retinopathy will develop bleeding into their vitreous cavity. This will cause significant blurring of vision and the appearance of black spots in the vision. If this occurs, it is often observed for a few weeks to months. Many of these bleeds will clear on their own. If it does not clear, one may need to have a vitrectomy, a surgery in which the vitreous gel and blood are removed from the eye.
When neovascularization proceeds untreated, the new vessels and scar tissue grow along the surface of the retina the back surface of the vitreous gel. This can lead to a tractional retinal detachment and ultimately blindness. This is a condition that often needs to be treated with surgery in the operating room. This is an outpatient procedure called a vitrectomy. The scar tissue and blood vessels are removed and laser is applied. While the retina can often be reattached, one’s visual potential will be limited due to the underlying nature of the diabetic eye disease.