Diabetes is a disorder of sugar utilization and storage which causes damage to blood vessels throughout the body. When blood vessels in the eye are affected, the condition is called diabetic retinopathy, the leading cause of blindness in patients 20 to 74 years of age. There are two stages of diabetic retinopathy: nonproliferative diabetic retinopathy and proliferative diabetic retinopathy.
Nonproliferative Diabetic Retinopathy (NPDR)
In nonproliferative diabetic retinopathy, the normally water-tight retinal blood vessels begin to leak. This causes blood, serum, and lipid to collect in the retina. If leakage is excessive, fluid builds up in the retina causing it to swell. This is called macular edema. Serum and lipid which leak may cause the formation of solid deposits in the retina called exudate.
Proliferative Diabetic Retinopathy (PDR)
Proliferative diabetic retinopathy is the more advanced form of diabetic retinopathy. In PDR, abnormal blood vessels begin growing from the surface of the retina into the vitreous gel, a condition called neovascularization. These abnormal vessels can break and bleed into the vitreous cavity, causing a vitreous hemorrhage. Symptoms usually include the appearance of spots, strands, or a curtain in the vision. The abnormal blood vessels may also cause scar tissue to form, which can block light from reaching the retina or pull on the retina causing a traction retinal detachment. Either of these complications may lead to severe loss of vision. A person with PDR may also have macular edema, as in NPDR.
Diabetic retinopathy, in its early stages, is often asymptomatic. When the disease (ischemia or edema) involves the central macula, the vision will decrease.
In proliferative diabetic retinopathy, scarring and bleeding interferes with the transmission of images to the retina and usually causes substantial decline in vision.
In addition to frequent, thorough eye exams, optical coherence tomography (OCT) may be used to detect macular edema. OCT is a scanning laser that images a slice of the retina in cross section.
Fluorescein angiography is another test used in which dye is injected into a vein in the arm. Digital images of the retina are obtained as the dye passes through blood vessels in the eye. Any abnormal blood vessels leak the injected dye, becoming detectable to the physician.
Ultrasonography allows an assessment of the retina behind a vitreous hemorrhage.
Focal laser treatment for macular edema is a painless in-office procedure during which laser energy is applied to areas of leakage. The goal is to decrease the swelling by diminishing leakage, thereby stopping the loss of vision. Most, but not all, patients show a beneficial response to laser treatment. In some cases, multiple laser treatments are required. Even when laser treatment successfully seals leaking vessels, new areas of leakage may arise later.
Intravitreal Drug Therapy
Intravitreal drug therapy is frequently recommended for treating macular edema. The goal of these injections is to make the retinal vessels less leaky. This treatment, administered at 6-8 week intervals, is very effective and can improve vision in many cases. In some patients, macular edema resolves completely following a brief series of intravitreal injections. Other, more severe diabetics, may require a more prolonged treatment regimen, sometimes lasting years. Intravitreal drug therapy has been proven to be the most successful way of managing diabetic macular edema.
Pars Plana Vitrectomy
Vitrectomy is effective for patients with diabetic macular edema. During this surgical procedure, the vitreous gel is removed. Fibrous membranes on the macula surface are also removed with the use of microscopic forceps. Following surgery, most patients experience a decrease in macular edema, along with improved vision.
Vitrectomy is also indicated in patients who develop vitreous hemorrhage or traction retinal detachment. During this procedure, the vitreous gel and blood are removed and microscopic forceps used to remove scar tissue. Leaking blood vessels are then cauterized or treated directly with laser. This is an outpatient procedure performed at the surgery center under local anesthesia. Most patients experience improvement in vision and eye health following vitrectomy.
Pan-Retinal Photocoagulation (PRP)
Pan-retinal photocoagulation is a laser treatment targeted at the peripheral retina, causing abnormal blood vessels to shrink. Although PRP can sometimes reduce night or side vision, it decreases the likelihood of bleeding, thereby reducing the risk of severe visual loss by up to 50%. PRP laser is an in-office procedure, often carried out over several sessions.
Treatment of diabetic retinopathy is very effective in limiting disease progression and subsequent vision loss. As with any treatment, complications may occur. Here is a partial list of the most common complications:
From the Expert…
The treatment for diabetic retinopathy has come a long way in the past forty years. Initially an untreatable, blinding disease, it is now quite responsive to therapy.
In the 1970’s and 80’s the development of laser photocoagulation limited vision loss from diabetic retinopathy.
Vitrectomy has evolved to treat scarring, bleeding, and retinal detachment with excellent results.
Intravitreal drug therapy has revolutionized the treatment of diabetic retinopathy. Now macular edema can usually be cured with return of vision common. This was unthinkable 15 years ago.
Of course the best treatment for diabetic retinopathy is prevention. Controlling blood sugar, blood pressure, and cholesterol will significantly reduce the risk of vision loss. It is recommended that patients take an active role in managing blood sugar, keeping hemoglobin A1C levels low, optimally 7 or less. A close relationship between patient and primary care physician is vital for preserving eyesight and overall health.
American Academy of Ophthalmology Retina/Vitreous Panel. Preferred Practice Pattern® Guidelines. Diabetic Retinopathy. San Francisco, CA: American Academy of Ophthalmology; 2017. Available at: www.aao.org/ppp. Accessed June 18, 2019.
Retina Health Series. Diabetic Retinopathy. The Foundation of the American Society of Retina Specialists. https://www.asrs.org/content/documents/fact_sheet_22_diabetic_retinopathy_new.pdf. Accessed July 9, 2019.
Summary Benchmarks for Preferred Practice Pattern® Guidelines. Diabetic Retinopathy. American Academy of Ophthalmology; 2018. Accessed June 17, 2019.