Welcome to HCM.
Check out a couple of things.
- did u have any injury/strain just before your ocular issue started?
- do you have double vision
/ hazy vision in both halves of the line?
- since you haven't mentioned your age, any systemic issues like diabetics/hypertension/ migraine
- Is it progressing?
It could be an acute PVD/ Retinal detachment(which requires an emergency management)/ simple flashes with vitreous fibrosis
noticed in your migraine episode( which can be observed).
I would recommend you to get an eye examination done at the earliest, with a detailed dilated fundus/retinal examination to know what it is. As previous 20/20 vision doesn't matter as this episode is a fresh one and needs attention now.
Lets hope your get relief soon. Take care.