Blackberry back light settings Blank screen - White...!!!.

ENSURE THAT ALL PLASTIC SCREEN COVERS ARE REMOVED
You might not have removed the plastic film off the screen; removing the plastic film resolves this issue.
MAKE SURE THAT THE BLACKBERRY SMARTPHONE IS FULLY CHARGED
Also verify that you have not had any issues with charging the BlackBerry smartphone. Some screen issues occur because the battery has not been fully charged. Charging the battery could resolve this issue.
CHECK THE LIGHT SENSOR
You might have an issue with the light sensor under the LCD screen.
To check that the light sensor is functioning, complete the following steps:

1. Cover the LED/light sensor with your thumb while the LCD screen is bright.
2. Hold your thumb in place until the LCD screen dims.
3. Uncover the LED/light sensor in bright light. The LCD should now be bright.

CHECK THE BACK LIGHT SETTING
The back light on the LCD screen might not function correctly.
To change the back light settings,complete the following steps:

1. On the Home screen, click Options.
2. Click Screen/Keyboard.
3. Set the following fields to adjust the settings:
   1. Back light Brightness
   2. Back light Timeout
   3. Automatically Dim Back light
   4. LED Coverage Indicator
4. Press the Menu key.
5. Click Save.

CHECK THE CONTRAST
Change the contrast and see if this solves the issues you are having. You can set the color contrast of application interfaces, menus, and dialog box to Normal, Gray scale, or Reverse Contrast.
To change the color contrast, complete the following steps:

1. On the Home screen, and then click Options.
2. Click Advanced Options.
3. Click Accessibility.
4. Set the Color Contrast field to Normal, Reverse Contrast, or GREY SCALE.
5. Press the Menu key.
   Click Save.