An Oklahoma man who admitted he tied-up, raped and sodomised a 13-year-old girl in a horrific sex assault has been spared a prison sentence because he is blind.

Benjamin Lawrence Petty, from Spencer, admitted charges including forcible sodomy, first-degree rape, and rape by instrumentation.

The 36-year-old has been sentenced to 15 years on probation despite the brutal rape at the Falls Creek summer camp in Texas in 2016, where he was working as a cook.

The court heard that Petty invited her into his cabin to perform magic tricks, before he tied her up and raped her.

"Petty closed the door to his bedroom, tied the (victim's) hands behind her back, pulled down her jeans, pushed her face down on his bed, and violently raped and sodomised her," court documents state.

Petty received three 15-year suspended sentences in exchange for his guilty plea, all of which will run concurrently, reported NewsOK.

Murray County Assistant District Attorney David Pyle, who negotiated the guilty plea deal, said Petty is "legally blind" which was a major factor in the decision to spare him prison time.

"The big thing is Mr. Petty is legally blind and the parents (of the victim) live out of state and this little girl lives out of state and didn't want to make all the travels back and forth," Pyle said.

"The plea was negotiated with their permission."

The attorney who representing the victim's interests in a civil case said the family were told by the district attorney's office that the rapist "would not serve any meaningful prison time due to his medical conditions" so agreed to the deal.

Bruce Robertson said according to KOFR News: "Based on this representation, the family did not object to the probationary sentence."

The family has also filed civil charges against the church that employed Petty to work as a cook and the church that brought their child to the camp.

Under the terms of Petty's probation the rapist will be required to wear an ankle monitor for 24 months, register as a sex offender and obtain treatment.