I'm sorry to hear you are struggling with your thoughts of going blind.

I'm not a doctor but I have experienced very similar situations with my eyes where there were shimmering lights and then boom, a bad headache. These are called migraine headaches and very often they can come from stress as well as other reasons too.

Since you went to your eye doctor and he said your retinas were absolutely healthy, I would say do your best to accept what the doctor told you (they have no reason to lie to you about such things) and look into the situation that it could have been a migraine. You can see your regular doctor about that. They will question you about what happened before you got your headache.

Oh, and the shimmering lights are called an aura. Migraine auras can come in different forms. Ask your doctor about those as well. To me, I appreciate getting the auras because then I'm able to take my migraine medicine before or just when the headache is hitting me so that it's not as bad as if I didn't take any meds.

I hope I've been able to help at least a little bit. Good luck with this and I hope you are able to calm your anxiety very soon.