Hypertropia is a type of strabismus, also known as misalignment of the eyes. Hypertropia happens when either eye drifts or looks upward. Infants' eyes usually align by the age of 2 to 3 months, even if the eyes seem to wander in newborns. What Causes Hypertropia? Hypertropia happens when the eye muscles are imbalanced and don't work together. The most common cause is weakness (called palsy) in the nerves in the brain that control eye movement. Some people are born with this eye weakness, but it can also happen later in life.