I can't tell you what caused the problem, there are a number of possibilities. The most common problem with Marfan's Syndrome is subluxated or dislocated lens. Another possibility if the diagonal lines lasted 5-20 minutes if Ocular or Eye Migraine. you need to start by seeing your Eye MD ophthalmologist now because this is a new symptom, after that you need to see your personal MD. If you want show this to your parents if they are reluctant.