Does anyone know at what age would entropion normally be diagnosed .Also if a dog has entropion and comes from lines clear of it could it be misdiagnosed ? .

Enbtropion can occur as a secondary condition to say an eye infection that causes the lid to swell and go into spasm, so care needs to be taken when diagnosing it as congenital and possibly inherited.  When entropion is inherited it generally affects both eyes. 

It isn't the condition itself that is inherited but the conformation that predisposes to it, e.g heavy facial features, deep set eyes etc, so breeds with such exaggerated facial features are more likely to show up with this condition, but it can occur in any breed out of the blue.

One would then carefully need to look at both parents to see if they have a tendency to exaggeration in this area that has been highlighted in the offspring.

Thanks Barbara , this makes sence now