I go to an ophthalmologist every year, and my vision's always excellent... don't need glasses or any of that.

All of a sudden twenty minutes ago, my left eye started to get kind of weird. It's blurry around the edges of the left visual field and when relaxed/looking ahead, I can see red, blue and green flecks and lines (which clearly don't actually exist). My right eye is totally fine.
Except for a massive headache that started around when the weird vision thing started, I'm totally fine.

Does anyone know what would cause this/what it is? And maybe how to get rid of it? It's really annoying, and I have somewhere I need to be in a couple of hours.

These are signs of a stroke. The flashes are also signs of a torn or detached retina. I hope you're online or you get this soon because I think you're going to miss your appointment in a couple of hours and head for the ER. Right Now!! It might be something simple (like a migraine headache), but it might not. Unless you're prone to migraines and have been diagnosed with them in the past, you must take this seriously.

This is a medical emergency. Please don't delay having it checked out!

I had something similar and it was a migraine event. Migraines can make you see weird things. I would take the time to go and have it checked out for sure. You don't want to be messing around with your brain or your eyesight.

These are signs of a stroke. The flashes are also signs of a torn or detached retina. I hope you're online or you get this soon because I think you're going to miss your appointment in a couple of hours and head for the ER. Right Now!!! It might be something simple (like a migraine headache), but it might not. Unless you're prone to migraines and have been diagnosed with them in the past, you must take this seriously.

This is a medical emergency. Please don't delay having it checked out!
I quoted this because I simply couldn't have said it better myself.

Does no one just go to the ER or their doctor ?

These are signs of a stroke. The flashes are also signs of a torn or detached retina. I hope you're online or you get this soon because I think you're going to miss your appointment in a couple of hours and head for the ER. Right Now!!! It might be something simple (like a migraine headache), but it might not. Unless you're prone to migraines and have been diagnosed with them in the past, you must take this seriously.

This is a medical emergency. Please don't delay having it checked out!

I again quote this as it is most likely the closest accurate reason for your change in vision. It is imperative that you seek medical treatment ASAP!1

More signs of a migriane than stroke, go get it checked out

This thread is 2 months old. We're not here to diagnose. Hopefully the OP went to the doctor.