I have seen an atrophic patch/scar in the retina

If the scar is inactive, there is no need to refer. Scars are common and some are of an unknown origin. Old toxoplasmosis scars are extremely common and require no treatment or investigation. A scar in isolation does not require referral, unless there is the suspicion of an active progressive process. Old toxoplasmosis scars can reactivate but this will be associated with other symptoms, such as blurred vision.