Restart

• The first step to take when you experience this problem is to attempt to shut off the iPhone, according to Apple Support. Pressing the Sleep/Wake button on the top of the iPhone should bring up the red power slider, which you can swipe to shut down the phone. However, due to the nature of the problem, you may not actually be able to see the red slider, which makes it impossible to turn off the device.
  
  

Reset

• In the event that you cannot shut down the phone, your next step should be to reset it, which is similar to rebooting a computer. Pressing the Sleep/Wake button and the Home button at the same time until the Apple logo appears will initiate a reset. This process makes it possible to restart the phone without using the touch screen. If the initial reset doesn't work, resetting the iPhone while it is connected to the computer may be more fruitful.
  
  

Restore

• When a hard reset does not fix the glitch, the final option is to restore the iPhone to factory settings. This process completely wipes the iPhone and reinstalls the basic operating system. You can immediately re-sync your media, but you will lose your personal settings and data. To perform a restore when the screen is white, the iPhone must be connected to the computer. The "Restore" button is located on the Summary page in iTunes, which you can bring up by clicking the iPhone under Devices on the left side of the iTunes browser.
  
  

Physical Damage

• Software glitches are not the only cause of a white screen; internal hardware damage can also make it appear. If the iPhone was recently dropped, exposed to extreme temperatures or soaked with liquid, it is likely that the white screen is a result of hardware damage. This type of damage cannot be solved at home, as it requires opening the iPhone and possibly replacing some parts. However, this type of damage, especially damage caused by liquids, is not typically covered by an Apple warranty.