In the early stages of diabetic retinopathy, you may have no symptoms. Vision may not change until the disease gets worse. Then you may have blurry or double vision; dark or floating spots; pain or pressure in one or both eyes; or rings, flashing lights, or blank spots in your vision.
A decrease in your central vision could be caused by macular edema which may occur from diabetic retinopathy. It happens when the macula, a part of the retina, swells from the leaking fluid and causes blurred vision. When new vessels grow on the surface of the retina, they can bleed into the eye. This may decrease vision.