My advice would be to see your optician again and your GP. Maybe you saw your GP after the optician suggested migraine? When I had what was finally diagnosed as optic neuritis, I had more of a problem with my tunnel vision in one eye, but no pain. My mum has glaucoma and I know that this usually affects periferal vision, but did worry at the time that this might be my problem. I will say it took a long time to go through various tests at the eye hospital before they sent me for an MRI that confirmed ON and multiple lesions on my brain. I wish I had gone to my GP as well as my optician and would suggest you do the same.
By the way my vision has almost fully restored itself, it was the complete numbness of my foot that finally got me to the GP and speeded up getting the results of the MRI (eye hospital postponed 2 post MRI consults!) Keep your GP in the loop, they will be your best advocate if further tests are needed.
Take care x