Diabetic Retina Management

1. Nonproliferative (background) diabetic retinopathy.
2. Proliferative diabetic retinopathy.

Nonproliferative (background) diabetic retinopathy (includes diabetic macular edema)

It is the earliest stage in the development of retinopathy. It is rare before 8-10 years of diabetes. At this stage vision is normal and there is no threat to sight.To understand diabetic retinopathy, you must understand the changes that occur in the retina from this disease.  The vessel itself consists of endothelial cells which make up the wall of the blood vessel surrounded by pericytes which make the blood vessel wall strong and keep the endothelial cells from leaking. In diabetes these cells (pericytes and endothelial cells) have problems with the glue that holds cells together and the cells themselves stop working properly.

As diabetic retinopathy (diabetic effects on the retina) progresses pericytes are lost and the endothelial cells' connections are not as strong as a normal vessel. These cells develop outpouchings called microaneurysms, begin to leak and sometimes the vessels completely block off. When a blood vessel closes, the area that blood was going to flow to becomes what we call "ischemic" which means that it is basically having a stroke (no oxygen getting to the tissue). As a result that area of retina may stop working or have difficulty working properly  (swollen retina from lack of oxygen). If all the changes that occur in the blood vessels are confined to the retina (loss of cells and leakage) then the retina may thicken in the area of leakage and if this is in the center of vision (macula) we call this clinically significant macular edema (CSME). This thickening of the retina, much like a dry sponge changing to a wet sponge, keeps the nervous tissue from working properly and decreases vision. All of the above changes occur within the retina and are considered "background" diabetic retinopathy (BDR). 

Proliferative diabetic retinopathy

When the retina is not getting enough oxygen this can stimulate the growth of new blood vessels and these new vessels usually do  not grow within the retina. They will grow out of the retina and along the surface of the vitreous or into the vitreous cavity and are called "neovascularization" (new vessels). Along with neovascularization, scar tissue may form and this scar tissue (fibrovascular proliferation) then grows on the surface of the retina and contracts causing a retinal detachment.

Another problem that can occur is that a new blood vessel can break and blood can fill the eye in what we call a vitreous hemorrhage. These later problems might require, in some instances, a vitrectomy to remove the vitreous hemorrhage or scar tissue that has occurred from this type of retinopathy. This is then "proliferative" (new vessels and scar tissue proliferating) diabetic retinopathy (PDR).

The most important tool for treating diabetes and its complications including diabetic retinopathy is medical management of the diabetes. Tight control of blood sugar and strict blood pressure control have been clearly demonstrated as critically important in helping to prevent the eye complications of diabetes and in slowing their progression. 

Once retinopathy has developed, laser surgery is currently the mainstay of treatment. Lasers have been used in the treatment of diabetic retinopathy for more than 20 years and their benefit has been clearly established by numerous well-designed studies. Laser surgery is an office outpatient procedure in which highly focused green laser light is aimed through a dilated pupil at the retina. Usually, the laser light is focused by treating through a contact lens placed on the patients eye. 

Laser treatment for diabetic macular edema

In treating diabetic macular edema, the goal is to help stabilize vision by attempting to stop the damaged blood vessels from leaking fluid into the retina causing it to swell. Usually this form of laser surgery helps stabilize vision rather than improving it (although sometimes it can). When indicated, laser treatment has been demonstrated to allow patients to maintain their vision longer than those left untreated. Both focal and grid laser treatment are done. Focal treatment is possible when there are a small number of discreet areas of leakage which can be targeted directly for treatment. The fluorescein angiogram is often used as a guide for this procedure. When the leakage is diffuse in nature, a grid pattern of laser may be used instead. Laser spots are applied in a grid pattern over the swollen areas of retina. After laser treatment, the patient may notice small spots in visual field caused by the laser energy. Over time, these spots will often become less noticeable to the patient. Its is important to recognize that the effects of laser are not immediate. It is possible that the vision may get a little worse shortly following laser but, in the long run, most of the patients who receive laser for macular edema will have better vision than if they hadn't received the treatment. 

Laser treatment for proliferative diabetic retinopathy 

The abnormal neovascular vessels (new blood vessels) of proliferative diabetic retinopathy are treated with panretinal (scatter) laser photocoagulation or PRP. This type of laser involves treatment to the peripheral retina which is not receiving adequate blood flow. It is believed that by treating these sick areas of retina the stimulus that drives the neovascular process may be halted. Since this treatment often involves many laser applications (often over 1,000) it may be divided into two or more separate sessions. This type of laser treatment is frequently successful in stopping the growth of the abnormal vessels and in some cases they may shrink. It is important to recognize that panretinal photocoagulation does not improve vision. It is intended to help prevent blinding complications of diabetic retinopathy. It is not without side effects. Some loss of side (peripheral) and color vision is normal following this type of treatment as is a decrease in night vision. Some patients will experience some generalized blurring of vision which is usually transient but may persist indefinitely. Since there are these side effects, panretinal photocoagulation should be performed only for specific indications which have been well established through clinical trials. Despite these side effects, when indicated, panretinal photocoagulation has been clearly shown to reduce the risk of severe visual loss in proliferative diabetic retinopathy. 


Vitrectomy surgery for proliferative diabetic retinopathy 

While panretinal photocoagulation is frequently successful in halting the proliferative process, some patients progress despite laser treatment. Other patients may have bleeding (vitreous hemorrhage) occur before laser can be applied which may prevent laser from being delivered to the back of the eye. Some of these eyes may ultimately require vitreous surgery. The main indications for vitrectomy in diabetic retinopathy are persistent vitreous hemorrhage and tractional retinal detachment secondary to proliferative disease. Vitrectomy surgery is considered a major eye operation. It involves removal of the vitreous gel from the cavity of the eye. Frequently, the retina has to be reattached by surgically dissecting the scar tissue membranes off the surface of the retina. Laser treatment is often applied at the time of vitrectomy. In some cases, a gas bubble is left in the eye following surgery to keep the retina flat against the back wall of the eye. These patients may be asked to position their head face down for a week or more following the surgery. The gas bubble is gradually absorbed and replaced by the eye's own fluid.