Abraham Lincoln suffered from double vision caused by intermittent vertical hypertropia. Biographers have speculated this, combined with his physical characteristics – notably his 6’4” frame – suggests the 16^th US president had Marfan syndrome, as did Lincoln’s great-great-grandfather.

Most people with Marfan syndrome suffer ocular defects including myopia, abnormal curvature of the eye, astigmatism, corneal thinning, flattened cornea, cataracts, glaucoma, strabismus or retinal detachment. However, authors of a 1999 Nature Medicine article wrote that these facts are not conclusively indicative of Marfan. Aside from the most obvious, Lincoln had more than his share of mishaps – smallpox; malaria (twice); syphilis; childhood near-drowning; and clubbed in the head by attackers in 1828, and twice more in the 1860s by his wife – which may have contributed to his intermittently upturned left eye. Vertical hypertropia is also consistent with failure of the superior oblique muscle, which could be attributed to trochlear nerve damage from a horse kick that concussed the nine-year-old Lincoln, according to the authors of a 2007 Archives of Ophthalmology paper.