Take-home: The goal of treatment for diabetic macular edema is to maintain or improve vision, but improvement of edema is a better metric for determining whether the treatment is having a benefit or failing.
Because diabetes is a growing epidemic, retina specialists can expect to treat more patients for diabetic macular edema (DME) in the future. Pharmacotherapy with anti-VEGF agents or a corticosteroid can be effective, but it helpful to have some criteria for defining treatment failure to guide decisions on changing therapy.
Recognizing the potential for lack of correspondence between structural and functional measures and how multiple factors can affect visual acuity, assessing failure of treatment for DME is best judged by persistence of macular edema identified with optical coherence tomography (OCT), said Patricia Udaondo, MD.
“The pathophysiology of DME is a very complex and involves VEGF and many inflammatory factors. Therefore, it may not respond to monotherapy,” explained Dr. Udaondo, Hospital Universitario y Politécnico La Fe Aiken, Valencia Spain. “Stabilizing and/or improving visual acuity is the main objective of any treatment in ophthalmology, including for DME. However, visual acuity can be an imprecise endpoint for evaluating treatment response because it can be influenced by confounding factors. Unlike visual acuity, change in the OCT is objective and independent of other factors.”
Visual acuity limitations
A ceiling effect in patients who have good baseline visual acuity (> 69 letters) is one reason why lack of improvement in visual acuity may not necessarily represent treatment failure. Alternatively, DME may improve in some patients without a corresponding improvement in visual acuity if there is permanent structural damage or, in the case of corticosteroid treatment in a phakic patient, because of treatment-induced cataractous changes.
Another situation to consider is the patient whose visual acuity improves to 20/20, but who still has residual edema on the OCT. “Is that patient a treatment responder because the visual acuity is good?,” Dr. Udaondo added.