What are the causes of waves in front of eyes?

Most likely migraine: Visual events described as wavy, zigzag, saw toothed, jagged, scintillating, often are a result of a migrainal event that has stimulating the visual path in the brain. They may or may not be associated with headache, nausea, vomiting or othe associated symptoms. To be sure, ; because you are diabetic, see your eye md for an exam to make sure it isn't a retinal issue.