How long do the flashes last? Do you see black things floating around also? What is your age? What other medical conditions do you have?
There are two prominent causes of flashing in eyes.
One is migraines. These usually last 15-20 minutes and may or may not be followed by a headaches.
The second is a vitreous pulling or detachment. There is a gel inside the eye. As you age or if you are very near-sighted (which you are), sometimes the gel breaks up into little pieces. It can also pull and tug on the retina. When it does this, you will see a flash of light. The little pieces then sometimes float around and are called floaters. This process is harmless. However, as the gel tug on the retina, sometimes it tears the retina which can lead to a retinal detachment (which is a major problem requiring surgery). It sounds like you are just having the gel tug on the retina some. It sounds harmless, but I would have your eye checked to make sure the retina is OK (not urgent).
I hope this helps and thank you.
You do need exams every year, especially if the symptoms are new or returning.
I'm not sure that the pain in left eye is related to the flashing. It could be from allergies, sinus, contact lens irritation, or not perfectly corrected contact prescription. This may explain why the glasses relieve some symptoms if the contacts are irritating or not fully corrected (especially if you have some astigmatism).
As far as the ictal tendency, this would only make sense if it is located to the occipital area of the brain.
What type of contacts are you wearing? There are newer more comfortable brands like Oasys or AO Aqua. If affordable, have you considered LASIK?
Bausch and Lomb is just the company name. They make many products. I'm not sure which you are using. They have the newest AO contacts that I think are the best. Acuvue also has Oasys that is pretty good too.