Understanding vision-threatening retinal conditions: Diabetic macular edema and wet AMD
Our scientists are researching new ways to address vision-threatening retinal conditions like diabetic macular edema and wet age-related macular degeneration (wet AMD)
October 9, 2025
Retinal conditions such as diabetic macular edema (DME) and neovascular (wet) age-related macular degeneration (AMD) threaten the eyesight of millions worldwide. While anti-VEGF treatments have helped to improve outcomes, a significant number of patients – up to 40% – fail to respond or only partially respond.
“A diagnosis of diabetic macular edema or wet age-related macular degeneration can profoundly affect a patient’s quality of life,” said Dr. David Guyer, founder, chief executive officer and president at EyeBio, a wholly-owned subsidiary of Merck & Co., Inc., Rahway, N.J., USA, “The fear of progressive vision loss looms large, and beyond the physical challenges, many patients carry the emotional burden of worrying about their declining eyesight.”
To find alternatives for these patients, our scientists are investigating novel therapeutic targets for certain retinal conditions.
Our research exploring the Wnt signaling pathway
Our eyes have a blood-retinal barrier that protects our delicate retinal tissue. When the barrier is compromised, fluid can leak into the macula – the central part of the retina responsible for sharp, detailed vision – and other areas of the eye, causing swelling that can lead to vision loss for people living with DME and wet AMD.
Research suggests that changes in the Wnt (pronounced “wint”) pathway are associated with the breakdown of this blood-retinal barrier in DME and wet AMD. MSD and EyeBio scientists are exploring the Wnt pathway as a potential approach to help improve the integrity of the blood-retinal barrier.
“We hear from retinal physicians about the demand for novel approaches to treat serious retinal conditions like diabetic macular edema and wet AMD.”
- Dr. Tony Adamis
Chief scientific officer, EyeBio, a wholly-owned subsidiary of Merck & Co., Inc., Rahway, N.J., USA
NOTE: These images are diagrammatic representations of the eye for illustrative purposes only.
What is diabetic macular edema (DME)?
Diabetic macular edema (DME) is serious eye condition that poses a risk to vision in people with diabetes:
- DME is caused by excess fluid buildup in the retina and characterized by swelling and thickening of the macula due to fluid leakage from damaged blood vessels.
- DME may be present in patients who are not experiencing visual symptoms, at times delaying a definitive diagnosis.
What is wet age macular degeneration (wet AMD)?
Wet AMD is the most frequent cause of vision loss in older adults, caused by the growth of abnormal blood vessels under the retina.
- Current therapies are limited to slowing or reducing AMD-associated vision loss.
Through research, our scientists hope to improve vascular stability and reduce fluid leakage. We are working to potentially redefine the treatment of certain retinal conditions to help patients worldwide.
Learn more about our research and commitment to ophthalmic health.