Intravitreal Ranibizumab or Triamcinolone Acetonide as Adjunctive Treatment to Panretinal Photocoagulation for Proliferative Diabetic Retinopathy

Proliferative diabetic retinopathy (PDR) is manifested in retinal neovascularization at the disc (NVD) or elsewhere (NVE). Vitreous hemorrhage or tractional detachment from PDR is a leading cause of severe visual loss and new onset blindness. Without intervention, 60 percent of individuals with diabetic retinopathy will eventually develop PDR, resulting in significant visual loss in nearly fifty percent.

Proliferative diabetic retinopathy is currently treated with panretinal photocoagulation (PRP) which destroys areas of the retina but preserves central vision. PRP is most effectively seen in a regression of new vessels, stabilization of the neovascularization, and reduced risk of visual loss. However, the treatment is associated with unavoidable side effects including macular edema with transient or permanent central vision loss, diminished vision loss, and night vision loss. The treatment applies laser burns to the peripheral retinal tissue, destroying outer photoreceptors and retinal pigment epithelium of the retina, and is thought to exert its effect by increasing oxygen delivery to the inner retina and decreasing viable hypoxic cells which are producing growth factors such as VEGF. Studies have implicated vascular endothelial growth factor (VEGF) as the substance leading to neovascularization and/or increased vascular permeability. Thus, it is reasonable to expect that inhibition of VEGF could reduce both PDR and transient vision loss from macular edema. There are several anti-VEGF drugs. Ranibizumab is the drug to be evaluated in this trial. In one trial of ranibizumab on DME, ten patients with chronic DME received a series of 0.5 mg intraocular injections. The treatments were well tolerated with no ocular or systemic adverse events. Since intraocular injections of ranibizumab significantly reduced foveal thickness and improved visual acuity in all ten patients, there is strong rationale to consider this drug as adjunctive therapy to PRP in a attempt to reduce the acute, transient edema that may occur with PRP.

Similarly, corticosteroids, a class of substances with anti-inflammatory properties, have demonstrated to inhibit the expression of VEGF. Triamcinolone acetonide is often used as a periocular injection for the treatment of cystoid macular edema (CME) secondary to uveitis. Clinically, triamcinolone acetonide is used in the treatment of proliferative vitreoretinopathy and choroidal neovascularization. Studies on patients with proliferative diabetic retinopathy randomly assigned to receive 4 mg triamcinolone 10 to 15 days prior to PRP treatment showed a reduction in central macular thickening, and fluorescein leakage was greater in the injection group than in the control group at 9 and 12 months follow up. Mean visual acuity improved by one line in the injection group and worsened by two lines in the control group.

In summary, there is strong rationale that using either intravitreal ranibizumab or intravitreal triamcinolone acetonide as an adjunct to PRP could reduce the magnitude of vision loss.

This study is being conducted to determine whether intravitreal injection of an anti-VEGF drug or an intravitreal injection of a corticosteroid can reduce the occurrence of macular edema and visual acuity impairment following PRP. Subjects will be randomly assigned with equal probability to one of the following three injection groups: