well, if you feel like you're up to it, replacing the backlight is possible. Call toshiba first and get a price for a new backlight. if you can afford it, it would be ALOT simpler to replace the whole LCD panel. meaning, the panel inside the LCD screen casing. you need to take the whole assembly off, remove the front bezel, and take out the LCD panel. a new LCD panel can cost in the range of 200-400 bucks.
the age of the laptop will definetely determine whether the work and the money involved is worth it...is it a newer laptop? or is it getting up there in years?
you can also search around on google and possibly find a repair or disassembly guide for that particular model.