In the presence of macular edema or proliferative diabetic retinopathy, a patient should receive immediate referral to an ophthalmologist experienced in treating diabetic retinopathy. Treatment usually involves surgical procedures — either laser photocoagulation surgery and/or vitrectomy.6 Laser surgery and appropriate follow-up care can reduce the risk of blindness by 90%.2 In some cases, it may even restore lost vision.
Two large NIH-funded clinical studies have shown promising results that laser photocoagulation therapy prevents vision loss in patients with diabetic retinopathy.
Results of the Diabetic Retinopathy Study showed that panretinal, or scatter, photocoagulation surgery reduced the risk for severe vision loss from proliferative retinopathy by 60% — from 15.9% in untreated eyes to 6.4% in treated eyes.8
Scatter laser treatment helps to shrink abnormal blood vessels and is most effective before damaged vessels begin to leak and bleed. The treatment involves placing between 1,000 to 2,000 laser burns in the areas of the retina away from the macula, causing the abnormal blood vessels to shrink. This procedure can produce some loss of side vision, night vision and color vision, but it is effective in preserving remaining eyesight.
Less-intensive focal photocoagulation surgery is used to treat macular edema. Instead of a thousand or more laser burns, focal laser surgery involves several hundred. Again, the burns are applied to blood vessels leakage surrounding the macula.
Results from the NIH-funded Early Treatment Diabetic Retinopathy Study showed that focal photocoagulation therapy preserves vision and reduces the risk of vision loss by 50% or more.
With both scatter and focal surgeries, treatments are delivered several weeks apart if both eyes are involved.
If the bleeding is severe, vitrectomy may be performed to remove blood from the center of the eye. During the procedure, the vitreous gel that has been contaminated with blood is removed. A salt solution replaces lost volume.
Panretinal laser photocoagulation may be done during vitrectomy to treat any underlying proliferative disease. Vitrectomy can accelerate development of cataracts and raise the risk of retinal detachment and endophthalmitis.
Injectable intraocular medications have been proposed for treating diabetic retinopathy and macular edema. Intraocular steroid injections, such as with triamcinolone, have been shown to improve visual acuity and retinal thickness in patients with refractory diabetic macular edema despite photocoagulation therapy.2,8
Also, anti-vascular endothelial growth factor (VEGF) drugs have been developed for the purpose of preventing new blood vessel formation. Elevated VEGF has been implicated in the development of diabetic retinopathy at all stages of disease, though it is found in the highest levels in proliferative diabetic neuropathy and macular edema.9
The FDA has approved several anti-VEGF medications for age-related macular degeneration, including pegaptanib (Macugen, Eye Tech Inc.) and ranibizumab (Lucentis, Genentech), but none have received approval in the treatment of diabetic retinopathy or diabetic macular edema.
But the small clinical trials that are available for these indications are encouraging. Results from the trial Ranibizumab in Diabetic Macular Edema With Center Involvement, a phase-2 study, showed that intravitreal ranibizumab improves visual acuity in diabetic macular edema.10 Similar results were recently presented for intravitreal pegaptanib and intravitreal bevacizumab.11
Interest remains high among researchers about the potential use of anti-VEGF medications in the treatment of diabetic retinopathy, particularly for macular edema, as part of combination therapy with photocoagulation surgery or for photocoagulation-refractory disease. However, results from large-scale trials are not yet available to endorse their use for this indication.
Researchers are also investigating anti-tumor necrosis factor agents, such as infliximab (Remicade, Centocor Ortho Biotech, Inc.), in diabetic macular edema with good results.12
Alice McCarthy is a freelance medical writer.
11. Arevalo JF. Curr Diabetes Rev. 2010; 6: 13-22.