Double vision can occur when the two eyes are not correctly aligned while aiming at an object, such as in esotropia and exotropia - these result in uncrossed diplopia and crossed diplopia, respectively (i.e. "crossed eyes", in esotropia, result in uncrossed diplopia). When the eyes are misaligned and aimed at different targets, two non-matching images are sent to the viewer's brain. When the viewer's brain accepts and uses two non-matching images simultaneously, double vision results.Double vision is dangerous to survival, therefore, the brain naturally guards against its occurrence. In an attempt to avoid double vision, the brain can ignore one eye (suppression). Due to the brain's ability to suppress one eye, double vision can appear to go away without medical evaluation or treatment. The causes of the double vision are very likely still present and loss of vision in one eye can occur due to lack of treatment. The loss of vision in one eye can be temporary or permanent depending on detection and treatment.