DVD error correction is found on the disc itself, not on the laser.
The DVD file structure has a BUP file that backs up the IFO file, so that even if the IFO is damaged, the player will read the data on the BUP file to get pointers as to how it should play the disc without an IFO.
Scratches can cause minor data errors that are easily corrected by a DVD's error correction system, which is 10 times more robust than a CD's error correction system.
However, a very small scratch on a DVD can sometimes be uncorrectable, while a very large scratch can be easily correctable. It all depends on the orientation and refraction of the scratch.