Ranibizumab and Peripheral Scatter Laser in Patients With Diabetic Macular Edema and Peripheral Nonperfusion

Diabetic retinopathy is a leading cause of moderate and severe visual loss in developed countries. It is of paramount socioeconomic impact as the prevalence of diabetes is sharply increasing, diabetic macular edema is the leading cause of vision loss in working age patients, it is a significant cause of vision loss in patients older than 65 years of age, it frequently affects patients bilaterally, and the costs of therapy are increasing.

Diabetic macular edema (DME) is the most common cause of vision loss in diabetic retinopathy. The pathophysiology of DME is complex and multifactorial. Chronic hyperglycemia, protein kinase C (PKC) formation, free radical accumulation, advanced glycation end-product (AGE) proteins, and ischemia-driven release of vascular endothelial growth factor (VEGF) are some of the better understood factors that contribute to chronic retinal arterial and capillary damage and increased permeability.

The RIDE and RISE Studies demonstrated the superiority of anti-VEGF monotherapy with ranibizumab over sham therapy, when all groups were allowed to receive macular laser therapy after month 3 based on predefined criteria. Furthermore, other studies have demonstrated VEGF inhibitors to be beneficial for DME, either as monotherapy or in combination with macular laser.

The benefit of VEGF antagonists in treating DME validates that the VEGF pathway is a key target. The need for repeated anti-VEGF injections to maintain the benefit of treatment begs the question whether persistent peripheral retinal ischemia may be driving VEGF production in at least a subset of patients with DME. Fluorescein angiographic studies of the mid- and far-periphery of diabetic patients by Shimizu in the 1980's demonstrated areas of peripheral retinal nonperfusion in diabetic patients. These findings have been reproduced and substantiated more recently utilizing a novel, commercially-available imaging system for ultrawide-field angiography (UWFA) that employs a scanning laser ophthalmoscope and an ellipsoidal mirror.

We investigated whether patients with diabetic macular edema associated with peripheral nonperfusion on UWFA would have improved visual acuity, resolution of retinal thickening on OCT, and durability of therapy using a novel strategy of a single intravitreal injection of Ranibizumab, a VEGF-A inhibitor + UWFA-guided peripheral Scatter Laser, or RaScaL. A second goal of the study was to guide DME treatment by the imaging signature of UWFA and OCT.

Inclusion criteria

Subjects will be eligible if the following criteria are met:

• Ability to provide written informed consent and comply with study assessments for the full duration of the study
• Age > 18 years

Patient related considerations:

• Patients with Type I or Type II diabetes

Disease related considerations:

• Study eye with clinically significant diabetic macular edema characterized by macular edema, peripheral nonperfusion, and absence of macular traction on clinical exam, UWFA, and OCT.
• Study eye with best corrected visual acuity between 20/40 (≤ 73 letters on Early Treatment of Diabetic Retinopathy Study (ETDRS) chart and 20/320 (≥ 19 letters on ETDRS chart) Other considerations
• Patient able to complete all study visits
• Female patients must be using two forms of contraception

Exclusion criteria

• Pregnancy (positive pregnancy test) or lactation. Premenopausal women not using adequate contraception. The following are considered effective means of contraception: surgical sterilization or use of oral contraceptives, barrier contraception with either a condom or diaphragm in conjunction with spermicidal gel, an Intra Uterine Device, or contraceptive hormone implant or patch.
• Prior enrollment in the study
• Any other condition that the investigator believes would pose a significant hazard to the subject if the investigational therapy were initiated
• Participation in another simultaneous medical investigation or trial
• Therapy with intravitreal triamcinolone, pegaptanib, ranibizumab, or bevacizumab within the previous 3 months
• Previous panretinal scatter laser photocoagulation
• Previous pars plana vitrectomy
• Visually-significant significant cataracts as primary reason for vision loss
• Uncontrolled or advanced glaucoma
• Patients on more than one anti-glaucoma agent
• Myocardial infarction or cerebrovascular accident within 6 months
• Subjects with poor glycemic control that have initiated intensive insulin treatment or plan to do so in the next 4 months