Misspell Last Name in VISA obtained 2 years ago

[makunag]

My parents got their 5 years visitor visa around 2 years ago, but beacause of some unavoidable circumstances they never came to USA. Now they want to come. And now they noticed that the last name of my father is mispelled in the VISA. Its just one letter mistake.
Will it be risky to let them come as it is ? Or I have to contact consulate and get it changed ? What is the procedure, as its been so long since they got visa? Searched Conulate/US State website couldn't find any info on that. Any help will be appreciated.
Thanks.

[Murali]

dont worry abt such small mistake as long as its not a big or toatally wrong name.
Such type of problems are known and common and doesnt create problem.

[makunag]

Thanks.