Ophthalmoparesis refers to weakness (-paresis) or paralysis (-plegia) of one or more extraocular muscles which are responsible for eye movements.

Internal ophthalmoplegia means involvement limited to the pupillary sphincter and ciliary muscle.

External ophthalmoplegia refers to involvement of only the extraocular muscles.

Ophthalmoparesis can result from disorders of various parts of the eye and nervous system: Thiamine deficiency can cause ophthalmoparesis in susceptible persons; this is part of the syndrome called Wernicke encephalopathy.

It can also be classified by the directions of affected movements, e.g. "vertical ophthalmoparesis".