The toddler was attacked by Alix Bluck, 22, who along with then partner James Bluck, 35, was supposedly caring for the child.
A shocked visitor said the child looked like a "Romanian orphan" as he lay on a mattress in a bare room.
When the child – who cannot be identified for legal reasons – was taken to hospital in Glasgow, medics discovered multiple bruising.
He was severely underweight and had brain haemorrhages and permanently reduced vision in his right eye from his ordeal.
Yesterday at the High Court in Edinburgh, the pair, of Kilmarnock, East Ayrshire, avoided jail. Alix Bluck was sentenced to 100 hours of unpaid work in the community and a three year supervision order.
Her ex-partner was also ordered to perform 100 hours unpaid work and told he would be supervised for one year.