Thank you for the photos! It doesn't look like its has light patches. It looks more like it has a large dark patch that makes the area around it look light. I'm no expert with screen issues, so I'm kind of taking a shot in the dark, but my guess is that your backlight has failed in that patch. The only option, therefore, would be to replace the backlight. I'm not sure about your model, but in some models, the backlight is integrated in the screen, necessitating the replacement of the entire screen. There is no information here on iFixit about replacing the screen or backlight, so you'd have to search the internet for a guide, or figure it out yourself. If you do decide to attempt this repair, make sure you take lots of pictures so you can [[Info:Repair Guide|create a guide|new_window=true]] and help other people who may be having similar problems.
Hope this helps!