What realistic options are there for adult on set of strabismus?

Adult strabismus. The cause needs to be analyzed. Is this destabilization of childhood strabismus? Or is this doubling of vision due to trauma, nerve damage, vascular malformation or tumor in the brain? You need to have a neuro-ophthalmologist sort this out and then decide on correction of the cause, or optical correction or surgical options.
Ask ophtalmologist. There are surgical correction and or injections of botox. Your best bet is to consult with an ophtalmologist dedicated to that: adult strabismus.
E. It depends why you have the strabismus and what the pattern is, but eye exercises, prism glasses and surgery can all be options. An ophthalmologist who specializes in adult strabismus, usually a neuro- or pediatric ophthalmologist could help you with this.