External ophthalmoplegia Progressive external ophthalmoplegia SNOMEDCT_US:46252003 HP:0000590 External ophthalmoplegia, progressive Progressive external ophthalmoplegia (PEO) can be regarded as a diagnosis, or as a feature of several other syndromes. The latter is the meaning of this term. UMLS:C0162674 HP:0000562 Initial bilateral ptosis followed by limitation of eye movements in all directions and slowing of saccades.