Phorias or tropias can be caused by a variety of factors. One of the most common causes is having a large amount of hyperopia or farsightedness. 3 When young children have high amounts of farsightedness that is undiagnosed, they struggle to see clearly.

How common is a phoria?

The overall prevalence and 95% CI of phoria, exophoria, and esophoria were 12.9% (10.7 to 15.6), 11.7% (9.6 to 14.3), and 1.2% (0.6 to 2.3), respectively. There was a significant difference in the overall prevalence of exophoria according to the age (0.021).

What causes vertical misalignment of eyes?

Hypertropia may be either congenital or acquired, and misalignment is due to imbalance in extraocular muscle function. The superior rectus, inferior rectus, superior oblique, and inferior oblique muscles affect the vertical movement of the eyes. These muscles can be paretic, restrictive (fibrosis) or overactive.