Exophoria can be caused by several factors, which include:

- Refractive errors - distance and near deviation approximately equal.

- Divergence excess - exodeviation is more than 15 dioptres greater for distance than near deviation.

- Convergence insufficiency - near exodeviation greater than distance deviation.

These can be due to nerve, muscle, or congenital problems, or due to mechanical anomalies. Unlike exotropia, fusion is possible in this condition, causing diplopia to be uncommon.

Among fifth and sixth grade children convergence insufficiency is 13%. In studies that used standardized definitions of Convergence insufficiency, investigators have reported a prevalence of 4.2% to 6% in school and clinic settings. The standard definition of Convergence insufficiency is exophoria greater at near than at distance, a receded near point of convergence, and reduced convergence amplitudes at near.

Exophoria is particularly common in infancy and childhood, and increases with age.

Strabismus can be seen in Down syndrome, Loeys-Dietz syndrome, cerebral palsy, and Edwards syndrome. The risk is increased among those with a family history of the condition.

Heterophoria is an eye condition in which the directions that the eyes are pointing at rest position, when "not" performing binocular fusion, are not the same as each other, or, "not straight". There can be esophoria, where the eyes tend to cross inward in the absence of fusion; exophoria, in which they diverge; or hyperphoria, in which one eye points up or down relative to the other. Phorias are known as 'latent squint' because the tendency of the eyes to deviate is kept latent by fusion. A person with two normal eyes has single vision (usually) because of the combined use of the sensory and motor systems. The motor system acts to point both eyes at the target of interest; any offset is detected visually (and the motor system corrects it). Heterophoria only occurs during dissociation of the left eye and right eye, when fusion of the eyes is absent. If you cover one eye (e.g. with your hand) you remove the sensory information about the eye's position in the orbit. Without this, there is no stimulus to binocular fusion, and the eye will move to a position of "rest". The difference between this position, and where it would be were the eye uncovered, is the heterophoria. The opposite of heterophoria, where the eyes are straight when relaxed and not fusing, is called orthophoria.

In contrast, fixation disparity is a very small deviation of the pointing directions of the eyes that is present while performing binocular fusion.

Heterophoria is usually asymptomatic. This is when it is said to be "compensated". When fusional reserve is used to compensate for heterophoria, it is known as compensating vergence. In severe cases, when the heterophoria is not overcome by fusional vergence, sign and symptoms appear. This is called decompensated heterophoria.

Heterophoria may lead to squint or also known as strabismus.

Convergence insufficiency or convergence disorder is a sensory and neuromuscular anomaly of the binocular vision system, characterized by a reduced ability of the eyes to turn towards each other, or sustain convergence.

When the fusional vergence system can no longer hold back heterophoria, the phoria manifests. In this condition, the eyes deviate from the fixating position.

People of all ages who have noticeable strabismus may experience psychosocial difficulties. Attention has also been drawn to potential socioeconomic impact resulting from cases of detectable strabismus. A socioeconomic consideration exists as well in the context of decisions regarding strabismus treatment, including efforts to re-establish binocular vision and the possibility of stereopsis recovery.

One study has shown that strabismic children commonly exhibit behaviors marked by higher degrees of inhibition, anxiety, and emotional distress, often leading to outright emotional disorders. These disorders are often related to a negative perception of the child by peers. This is due not only to an altered aesthetic appearance, but also because of the inherent symbolic nature of the eye and gaze, and the vitally important role they play in an individual's life as social components. For some, these issues improved dramatically following strabismus surgery. Notably, strabismus interferes with normal eye contact, often causing embarrassment, anger, and feelings of awkwardness, thereby affecting social communication in a fundamental way, with a possible negative effect on self esteem.

Children with strabismus, particularly those with exotropia (an outward turn), may be more likely to develop a mental health disorder than normal-sighted children. Researchers have theorized that esotropia (an inward turn) was not found to be linked to a higher propensity for mental illness due to the age range of the participants, as well as the shorter follow-up time period; esotropic children were monitored to a mean age of 15.8 years, compared with 20.3 years for the exotropic group. A subsequent study with participants from the same area monitored congenital esotropia patients for a longer time period; results indicated that esotropic patients "were" also more likely to develop mental illness of some sort upon reaching early adulthood, similar to those with constant exotropia, intermittent exotropia, or convergence insufficiency. The likelihood was 2.6 times that of controls. No apparent association with premature birth was observed, and no evidence was found linking later onset of mental illness to psychosocial stressors frequently encountered by those with strabismus.

Investigations have highlighted the impact that strabismus may typically have on quality of life. Studies in which subjects were shown images of strabismic and non-strabismic persons showed a strong negative bias towards those visibly displaying the condition, clearly demonstrating the potential for future socioeconomic implications with regard to employability, as well as other psychosocial effects related to an individual's overall happiness.

Adult and child observers perceived a right heterotropia as more disturbing than a left heterotropia, and child observers perceived an esotropia as "worse" than an exotropia. Successful surgical correction of strabismus—for adult patients as well as children—has been shown to have a significantly positive effect on psychological well-being.

Very little research exists regarding coping strategies employed by adult strabismics. One study categorized coping methods into three subcategories: avoidance (refraining from participation an activity), distraction (deflecting attention from the condition), and adjustment (approaching an activity differently). The authors of the study suggested that individuals with strabismus may benefit from psychosocial support such as interpersonal skills training.

No studies have evaluated whether psychosocial interventions have had any benefits on individuals undergoing strabismus surgery.

The causes of exotropia are not fully understood. There are six muscles that control eye movement, four that move the eye up and down and two that move it left and right. All these muscles must be coordinated and working properly in order for the brain to see a single image. When one or more of these muscles doesn't work properly, some form of strabismus may occur. Strabismus is more common in children with disorders that affect the brain such as cerebral palsy, Down syndrome, hydrocephalus, and brain tumors. One study has found that children with exotropia are three times more likely to develop a psychiatric disorder in comparison with the general population.

Exotropia is a form of strabismus where the eyes are deviated outward. It is the opposite of esotropia and usually involves more severe axis deviation than exophoria. People with exotropia often experience crossed diplopia. Intermittent exotropia is a fairly common condition. "Sensory exotropia" occurs in the presence of poor vision. Infantile exotropia (sometimes called "congenital exotropia") is seen during the first year of life, and is less common than "essential exotropia" which usually becomes apparent several years later.

The brain's ability to see three-dimensional objects depends on proper alignment of the eyes. When both eyes are properly aligned and aimed at the same target, the visual portion of the brain fuses the forms into a single image. When one eye turns inward, outward, upward, or downward, two different pictures are sent to the brain. This causes loss of depth perception and binocular vision. There have also been some reports of people that can "control" their afflicted eye. The term is from Greek "exo" meaning "outward" and "trope" meaning "a turning".

Dissociation refers to the situation where the innervation of one eye causes it to move involuntarily and independently of the other eye. Usually both eyes work together as described by Hering's and Sherrington's laws of innervation. A DVD is a slow upward and sometimes temporal movement of one eye, with cortical suppression of the vision in that eye while it is deviated. On returning downward and possibly inward to take up fixation, the DVD slow movement will be reversed.

The dissociative movement seen 'objectively' should not be confused with the dissociation that occurs 'subjectively' - as when the brain begins to not visualise both images simultaneously (by ignoring or suppressing vision in that eye).

DVD typically becomes apparent between 18 months and three years of age, however, the difficulties of achieving the prolonged occlusion required for accurate detection in the very young, make it possible that onset is generally earlier than these figures suggest.