New blood vessels are characteristic of proliferative diabetic retinopathy. Photo credit: Community Eye Health Journal Vol. 24 No. 75 SEPTEMBER 2011.
By Rebecca Salowe
Scheie Vision Summer 2020
A recent publication in JAMA Ophthalmology compared visual field changes in patients with proliferative diabetic retinopathy after random assignment to two treatment groups. This report was led by Maureen Maguire, PhD, the Carolyn F. Jones Professor of Ophthalmology and Director of the Center for Preventive Ophthalmology & Biostatistics.
Diabetic retinopathy is a complication of diabetes that can occur when high blood sugar levels cause damage to blood vessels in the retina. Proliferative diabetic retinopathy (PDR), a more severe form of the disease, involves the growth of new, abnormal blood vessels in the retina. These blood vessels can leak into the vitreous or form scar tissue that may lead to retinal detachment.
Historically, PDR has been treated with a laser therapy called panretinal photocoagulation, which makes many tiny burns (>1,000) to prevent abnormal blood vessels from growing and leaking. One of the side effects of these burns, however, can be the loss of peripheral vision.
More recently, anti-VEGF (vascular endothelial growth factor) drugs have emerged as an alternative treatment approach for PDR and other diseases involving ocular neovascularization. By targeting and inhibiting VEGF, a protein involved in the formation of blood vessels, this treatment helps to block growth signals to generate new, abnormal blood vessels. Though patients must receive frequent injections to maintain therapeutic benefit, one merit of this approach is thought to be the preservation of the peripheral visual field.
In order to understand which treatment approach—laser or anti-VEGF injections—leads to the best visual outcomes in PDR patients, Dr. Maguire and her team conducted an analysis of patients in these two treatment groups. They analyzed data from a clinical trial (“Protocol S”) conducted by the DRCR Retinal Network at 55 sites across the United States.
This study included 234 eyes randomly assigned to either treatment group. Patients in the laser group could receive anti-VEGF injections if diabetic macular edema emerged. Similarly, if patients in the anti-VEGF group reached “failure and futility” criteria, they could receive a laser treatment.
Both groups maintained good visual acuity after five years of monitoring, with low rates of complications. Overall, the magnitude of visual field loss experienced by the anti-VEGF group was lower than the level observed in the panretinal photocoagulation group.
Important differences in the pattern of visual field loss also emerged between groups. The laser group had large losses of visual field at the one-year mark, followed by further decline over the next four years. In contrast, the group receiving anti-VEGF injections had little loss of visual field at the two-year visit, but lost visual field over the next three years.
The losses in the anti-VEGF group were unexpected. Of note, these losses were still seen even when the patients who received laser treatments at a later point, due to the severity of their disease, were removed from the cohort.
Possible reasons for the losses seen in patients solely receiving anti-VEGF injections are increasing retinal ischemia (inadequate blood supply) due to underlying diabetes, greater cumulative number of injections, or a decrease in injections in later years, allowing PDR to take its natural course.
“Both anti-VEGF treatment and laser treatment can be very effective for treatment of PDR,” said Dr. Maguire. “With regular follow-up to assess the need for additional treatment, both can provide excellent visual acuity. Patients and their ophthalmologists need to consider the immediate side effects of laser, such as loss of visual field, and the need for multiple injections with anti-VEGF treatment, when choosing a therapy.”