After being diagnosed with hemiplegic migraine i still get yellow flashing in right eye, tv mobile fone noise can trigger this how can i stop this?

Avoid trigger!: Avoid anything that triggers the migraine, most common is caffeine, chocolate, stress. It could be anything though, try and notice and you may be able to decrease the onset of the migraines.

Migraine Meds: Sounds like the visual aura from a migraine. Speak with your neurologist to make sure nothing is wrong with your vision first. If he/she thinks it migrainous, you can have your migraine meds adjusted to try to counter this.