1,2 Old photographs can help you distinguish congenital Horner's by documenting heterochromia that was present at birth. If a patient presents with recent onset ptosis, your first suspicion should include cranial third-nerve palsy. Even if there is no complaint of diplopia, this entity should be considered. In some instances, the ptotic eyelid can block vision sufficiently to prevent the perception of diplopia. If palsy is not present and you observe anisocoria that's exaggerated in dim illumination, then Horner's syndrome is the likely cause.
Pharmacological testing is then necessary to confirm the diagnosis and localize the lesion.
This solution acts as an indirect sympathomimetic agent. Evaluate the test 15-30 minutes after instilling the drops to ensure accuracy. Eyes that fail to dilate or that dilate poorly have Horner's syndrome. Since cocaine can inhibit the uptake of these two medicines and reduce accuracy, you should wait 24-48 hours after the cocaine test before instilling either of these two agents. These agents release the endogenous neurotransmitter norepinephrine from the presynaptic vesicles.