If your optometrist said all is ok but your having light flashes did you mention it to the doctor? If not tell him about this for sure. I dont think you have anything to worry about as i have some light flashes sometimes. Just last week i was looking at some blue christmas lights at night and later for about 10 minuits i was seeing blue flashes out of the corner of my eye. I think its normal but if you worried do mention it to the doctor.
The most common source of flashes would be migraine.
To keep migraines away and also protect your eye health, take supplements. Whole-food supplements are best. Go to the healthfood store and have them help you find one that is suitable for you, and make sure it contains lutein for eye health.
Take a separate magnesium supplement every day and I think your migraines will go away.
I don't exactly have light flashes, I am just curious to know what they are.
Unless you have had an accident with a head injury, chances of someone your age having RD is very low. Flashing lights could be from anything, including migraines. You can have an optical migraine without having a headache, which most people grow out of, as they get older. If you have flashing, followed by dark spots covering your vision in one spot, then you need to be seen ASAP. Otherwise, I think you need to relax about this and try not to worry so much.