This study tests tonabersat, a pill that might help people with diabetic macular edema (DME), a condition where fluid builds up in the eye, affecting vision. The study compares tonabersat to a placebo (a pill that does nothing) to see if it reduces the thickness of the fluid in the eye over 6 months. The study also looks at kidney health to see if there are any benefits.

• The study lasts 6 months and involves taking a pill.
• Participants must have diabetes and good vision in at least one eye.
• Participants cannot have had certain eye surgeries or treatments recently.

Adults with type 1 or 2 diabetes and a specific eye condition can join if they meet certain criteria, like having good vision and no recent major eye surgeries. It's important to note that if you've had other treatments for DME or certain health conditions, you may not be eligible. This study helps researchers decide if a bigger study on tonabersat is needed. Participants won't get any treatment during the first 6 months, so it's important to be okay with that before joining.