David McFeeters, 70, first attacked the girl at an address on Benbecula in the Western Isles when she was just eight. The abuse continued for three years.
At Stranraer Sheriff Court, Sheriff Kenneth Robb said former driving instructor McFeeters, of Essex, had betrayed the trust of the girl, who is now 18.
The court heard the abuse claims were only brought to the attention of the police after his wife's death in 2011. She had been diagnosed with Alzheimer's Disease.
Murray Macara, QC, said the health of McFeeters had also declined. He has had a triple heart bypass and he has developed sleep apnoea. He added: "He acknowledges this is a serious matter aggravated by a breach of trust."
McFeeters admitted using lewd, indecent and libidinous practices and behaviour towards the girl between August 1, 2003, and August 31, 2006.
At an earlier hearing his plea of not guilty to abusing a 12-year-old girl at an address in Stranraer was accepted.
He was sentenced to 38 months in prison and placed on the sex offenders register indefinitely.