The earliest retinal changes of diabetic retinopathy are called non–proliferative or background diabetic retinopathy and result from damage to the small blood vessels in the retina. At first these vessels may begin to bleed and leak fluid into the surrounding retinal tissue. In the earliest stages of this condition, the patients usually have no symptoms and have 20/20 vision. A qualified practitioner, such as a general ophthalmologist or retinal specialist, may detect these changes by performing a dilated eye examination.

The doctor looks for small spots of bleeding or areas of retinal swelling due to fluid leakage. Sometimes, fatty material leaks from damaged vessels and collects in the retina as deposits called exudates. The ophthalmologist will often take color photos of the back of the eye to document the retinal changes. Non–proliferative diabetic retinopathy is further sub–divided into mild, moderate, and severe depending on the number and amounts of bleeding and leaking areas.

Frequently, especially if there is reduced vision, the ophthalmologist may elect to investigate the retinal changes further with a special diagnostic test known as a fluorescein angiogram. This test involves injecting a yellow dye into an arm vein and photographing the back of the eye as the dye passes through the retinal circulation. This test is especially useful for identifying areas of blood vessel damage and abnormal leakage from them. The test does not involve the use of X–rays. Patients should be aware that their urine will be bright yellow for a day or two following the injection.

Optical Coherence Tomography

Optical Coherence Tomography (OCT) is another test that is commonly obtained in order to assess fluid accumulation (macular edema) in the retina in patients with diabetes. OCT can demonstrate areas of retinal thickening and can be a useful tool in assessing a patients response to a treatment.

Macular Swelling (Oedema)

In some cases of non–proliferative diabetic retinopathy, enough leakage may occur in the retina to cause it to become swollen with fluid. This condition is called diabetic macular edema. Macular edema is the most common cause of vision loss in patients with diabetes, occurring in upwards of 10% of all diabetic patients. Patients with diabetic macular edema experience reduced vision in the form of blurring, darkening or distorted images. Often the amount of retinal and macular edema, and associated symptoms, will be unequal between the two eyes.

The treatment of diabetic macular edema is rapidly evolving. Treatment options include focal laser photocoagulation and intraocular injections of steroids or other medications such as Lucentis.

Treatment of Diabetic Retinopathy

Laser Surgery
Once certain levels of retinopathy have 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–based outpatient procedure in which highly focused green, yellow, red or infrared 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 patient’s eye. Anaesthetic eyedrops are usually all that is required to keep the patient comfortable. Laser surgery is used to treat both diabetic macular edema and proliferative diabetic retinopathy.

We currently use the PASCAL (Pattern Scan Laser) to deliver highly precise laser in various patterns at a fraction of the burn energy compared to conventional laser photocoagulation. The main advantages are: efficient and regular placement of burns; comfort and tolerance; faster speed; and less side effects (www.optomedica.com). 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 surgery has been demonstrated to allow patients to maintain their vision longer than those left untreated. Both focal and grid laser surgery are used in the treatment of diabetic macular edema. 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. It 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.

Injection of Intraocular Steroids and Other Medications

Lucentis & Other Anti-VEGF Therapy

Recently, the intraocular injection of anti–vasogenic drugs, that tell blood vessels to stop growing and leaking, has shown promising results in the control of retinal neovascularization and retinal edema. One such medication is Lucentis (ranibizumab). Intraocular injections of Lucentis have shown promising early results, and a good safety profile, in the control of retinal swelling and neovascularization due to a variety of retinal conditions including diabetes. Lucentis lasts about 4 weeks in the eye after a single injection and the injection may need to be repeated if the disease reactivates.

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 is advisable to divide the treatment 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.

Panretinal laser 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. 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. The vast majority of vitreous hemorrhages that are due to diabetic retinopathy will be absorbed by the body and clear on their own. If a vitreous hemorrhage does not clear on its own after about six weeks, then vitrectomy surgery to remove that blood may be indicated. Vitrectomy surgery is also indicated if the abnormal blood vessels and scar tissue contract and pull enough to cause a tractional retinal detachment.

A vitrectomy is a common retinal surgery in which the vitreous gel is removed with the aid of tiny surgical instruments in the operating room. If scar tissue has accumulated on the retina small instruments are used to peel the scar tissue off of the surface of the retina to relieve the traction. Once the blood is removed, laser is usually added to the side part of the retina during the surgery. The goal of surgery for a traction retinal detachment is to try to stabilize the vision and decrease the chance of the vision worsening.

A vitrectomy is performed in the operating room while you are sedated and your eye is numb. The surgery takes about one to two hours and patients go home that night. The surgeon may place a gas bubble in the eye at the end of surgery to act as a splint to keep things in place as they heal. The gas bubble will be slowly absorbed by your body over several weeks. It is important to note that if a gas bubble is left in the eye patients canno fly and must stay at sea level until the gas disappears.