Your symptoms sound consistent with a migraine headache. People who have had typical migraine headaches in the past can have the character of their migraine phenomena change to where they just have the typical "light show" associated with migraines. This light show can include these colored blobs, shades or shadows with shimmering lights around them, and also tend to come along with some of the other side effects of the migraines: light and/or noise sensitivity, nausea, irritability.
While you may not be having significant headaches, these sound like migraines without the headaches (for the most part), or what's called acephalgic migraines. Migraine headache medicine can be prescribed by your primary care doctor that can help you prevent these from happening, and can also abort them once they start. I would suggest starting with your PCP.
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