In a recently televised town hall, the live audience raised concern when former vice president Joe Biden's eye began to change colors. As the presidential candidate spoke, the white part of his eye began to turn red. Shortly after the incident media reports exploded, questioning Biden's health and relating the incident to previous health concerns. 

The eye condition Biden experienced is called a subconjunctival hemorrhage. In this condition, a very small blood vessel on the outer surface of the eye breaks, allowing blood to pool just beneath the surface.  This same process occurs in bruises.  However, in an eye, the outer most layer is clear, so the blood appears much brighter than in a bruise, which can be frightening.  Isolated occurrences of subconjunctival hemorrhages are not typically indicative of any serious pathology.  They can arise from episodes of coughing, sneezing, valsalva, rubbing, and are more common in people who are taking blood thinning medications. Subconjunctival hemorrhages are almost always painless and do not impact vision.  There is no treatment, but they will usually resolve fully within a few days to weeks.  

Here you can find more information along with a photo of the former vice president during the town hall appearance.