Do you see flashing lights with this stringy thing? What other medical conditions do you have? How is your vision?
To answer your questions, occasionally I have seen glimpses of flashing lights, yes. However the flashing light thing is not continuous as this stringy thing is continuous.
I am very health conscious and take supplements every day. I am large boned and 5'3" and weight 150 pounds. While I am usually busy doing first one thing and then another, I do not exercise on a daily basis, nor do I go to the gym. I was diagnosed with hypolowthyroid over a year ago, but do not take the medicine as I now do not have insurance. I do not know whether or nor these things are relevant however to the eye mystery.
You are experiencing what is called a posterior vitreous detachment. There is a gel in the back of the eye that you are born with, called the vitreous. As you age, the gel breaks into little pieces and float around. Sometimes as it is breaking up, it can tug on the retina; and this causes you to see a flash of light. All of this is harmless, although can be annoying. If you can make it to see an eye doctor, it would be helpful to make sure the retina is OK from this vitreous pulling on it. However, if you have a swarm of new floaters or flashing lights or shadows coming across your vision, you should have your eye checked right away.
On another note, the Lion's Club is very good with paying for eye exams and/or glasses for those who are uninsured and are below a certain income level. Likewise, the American Academy of Ophthalmology has a program called EyeCare America (www.eyecareamerica.org) that also supplies uninsured people with free eye exams through volunteer ophthalmologists. In terms of medications, many drug companies have indigent programs where they will supply you with free medications if you qualify. I am concerned about your not taking thyroid medications. This can have serious implications for your health.
Hope this helps and thank you.