<unk> , is a class of rare genetic disorders affecting one or more of the<unk>  that move the eyeballs. Individuals with<unk>  have varying degrees of ophthalmoplegia (an inability to move the eyes in one or more directions) and ptosis. The condition is present from birth and non-progressive, runs in families, and usually affects both eyes similarly. In the most common form, the superior recti are dysfunctional and the inferior recti, lacking proper opposition, pull the eyes down, forcing the head to be tilted upward in order to see straight ahead. There are three types of<unk> , numbered 1-3.<unk> 1, the most common type, is now known to be caused by one of several mutations in the KIF21A gene, while<unk> 2 is caused by mutations in the PHOX2A gene.<unk> 3 is caused by mutations in the TUBB3 gene.<unk>  was first named in 1956, although papers describing conditions now known or assumed to be<unk>  appear in the medical literature as early as 1840. Due to its rarity, it has been independently cited numerous times under many different names.
Congenital fibrosis of the extraocular muscles
Blast-related ocular trauma
Autoimmune inner ear disease
Late congenital syphilitic oculopathy
Effects of long-term contact lens wear on the cornea
Pachychoroid disorders of the macula
Oculomotor nerve palsy
Recurrent painful ophthalmoplegic neuropathy