The symptoms you describe could well be the side effects of a severe migraine. Migraine headaches may be preceded by a visual aura, lasting for 20 to 30 minutes, and then proceeding to the headache.
Some people, however, experience the aura but do not have a headache. This visual aura can be very dramatic. Classically, a small blind spot appears in the central vision with a shimmering, zigzag light inside of it. This enlarges, and moves to one side or the other of the vision, over a 20 to 30 minute period. When it is large, this crescent shaped blind spot containing this brightly flashing light can be difficult to ignore, and some people fear that they are having a stroke. In reality, it is generally a harmless phenomenon, except in people who subsequently get the headache of migraine. Since migraine originates in the brain, the visual effect typically involves the same side of vision in each eye, although it may seem more prominent in one eye or the other.
There are different variations of this phenomenon, with the central vision being involved, or with the visual effect similar to heat rising off of a car. Some people describe a kaleidoscope effect, with pieces of the vision being missing. All of these variations are consistent with ophthalmic migraine.
Although this is the most likely cause of your symptoms there are many things that can bring on problems with vision and strange shapes and flashing lights in your eyes. There could be a problem with the retina for example. You should seek the advice of an optometrist as soon as possible and if this is not possible then a doctor as if this is a serious problem, action may need to be taken immediately to prevent further damage.
Some people, however, experience the aura but do not have a headache. This visual aura can be very dramatic. Classically, a small blind spot appears in the central vision with a shimmering, zigzag light inside of it. This enlarges, and moves to one side or the other of the vision, over a 20 to 30 minute period. When it is large, this crescent shaped blind spot containing this brightly flashing light can be difficult to ignore, and some people fear that they are having a stroke. In reality, it is generally a harmless phenomenon, except in people who subsequently get the headache of migraine. Since migraine originates in the brain, the visual effect typically involves the same side of vision in each eye, although it may seem more prominent in one eye or the other.
There are different variations of this phenomenon, with the central vision being involved, or with the visual effect similar to heat rising off of a car. Some people describe a kaleidoscope effect, with pieces of the vision being missing. All of these variations are consistent with ophthalmic migraine.
Although this is the most likely cause of your symptoms there are many things that can bring on problems with vision and strange shapes and flashing lights in your eyes. There could be a problem with the retina for example. You should seek the advice of an optometrist as soon as possible and if this is not possible then a doctor as if this is a serious problem, action may need to be taken immediately to prevent further damage.