My left eye has been doing this weird light refraction for the past twenty minutes. what is causing it?

Probably migraine: Occipital migraine can produce an entertaining greying out of vision on 1/2 of the field of vision of both eyes (check this by covering each eye in turn) with a light flickering pattern surrounding the grey-out last 2 minutes to an hour or so. These are benign but annoying and are rarely so often as to require treatment. Wait it out and if it leaves you needn't worry. Otherwise see your eyemd.