Samsung UE55JU7090 - LED or Direct-lit issue?

hi,

just bought this used TV - Samsung UE55JU7090

i use it as my Computer Monitor.

But i have detected an darker area in the middle of the tv.

It´s kinda darker circle ~ Ø 30-40cm.

The firmware is T-HKMDEUC-1580.0

what can be done?

Thanks

cheers^^