When strabismus is congenital or develops in infancy, it can cause amblyopia, in which the brain ignores input from the deviated eye. Even with therapy for amblyopia, stereoblindness may occur. The appearance of strabismus may also be a cosmetic problem. One study reported 85% of adult strabismus patients "reported that they had problems with work, school, and sports because of their strabismus." The same study also reported 70% said strabismus "had a negative effect on their self-image." A second operation is sometimes required to straighten the eyes.

Medication is used for strabismus in certain circumstances. In 1989, the US FDA approved Botulinum toxin therapy for strabismus in patients over 12 years old. Most commonly used in adults, the technique is also used for treating children, in particular children affected by infantile esotropia. The toxin is injected in the stronger muscle, causing temporary and partial paralysis. The treatment may need to be repeated three to four months later once the paralysis wears off. Common side effects are double vision, droopy eyelid, overcorrection, and no effect. The side effects typically resolve also within three to four months. Botulinum toxin therapy has been reported to be similarly successful as strabismus surgery for people with binocular vision and less successful than surgery for those who have no binocular vision.

The prognosis for each patient with esotropia will depend upon the origin and classification of their condition. However, in general, management will take the following course:

1. Identify and treat any underlying systemic condition.

2. Prescribe any glasses required and allow the patient time to 'settle into' them.

3. Use occlusion to treat any amblyopia present and encourage alternation.

4. Where appropriate, orthoptic exercises can be used to attempt to restore binocularity.

5. Where appropriate, prismatic correction can be used, either temporarily or permanently, to relieve symptoms of double vision.

6. In specific cases, and primarily in adult patients, botulinum toxin can be used either as a permanent therapeutic approach, or as a temporary measure to prevent contracture of muscles prior to surgery

7. Where necessary, extra-ocular muscle surgery can be undertaken to improve cosmesis and, on occasion, restore binocularity.

Suppression may treated with vision therapy, though there is a wide range of opinions on long-term effectiveness between eye care professionals, with little scientific evidence of long-term improvement of suppression, if the underlying cause is not addressed (strabismus, amblyopia, etc.).

A determination of the prevalence of anisometropia has several difficulties. First of all, the measurement of refractive error may vary from one measurement to the next. Secondly, different criteria have been employed to define anisometropia, and the boundary between anisometropia and isometropia depend on their definition.

Several studies have found that anisometropia occurs more frequently and tends to be more severe for persons with high ametropia, and that this is particularly true for myopes. Anisometropia follows a U-shape distribution according to age: it is frequent in infants aged only a few weeks, is more rare in young children, comparatively more frequent in teenagers and young adults, and more prevalent after presbyopia sets in, progressively increasing into old age.

One study estimated that 6% of those between the ages of 6 and 18 have anisometropia.

Notwithstanding research performed on the biomechanical, structural and optical characteristics of anisometropic eyes, the underlying reasons for anisometropia are still poorly understood.

Anisometropic persons who have strabismus are mostly far-sighted, and almost all of these have (or have had) esotropia. However, there are indications that anisometropia influences the long-term outcome of a surgical correction of an inward squint, and vice versa. More specifically, for patients with esotropia who undergo strabismus surgery, anisometropia may be one of the risk factors for developing consecutive exotropia and poor binocular function may be a risk factor for anisometropia to develop or increase.

Refractive surgery causes only minimal size differences, similar to contact lenses. In a study performed on 53 children who had amblyopia due to anisometropia, surgical correction of the anisometropia followed by strabismus surgery if required led to improved visual acuity and even to stereopsis in many of the children ("see:" Refractive surgery#Children).

Young children with strabismus normally suppress the visual field of one eye (or part of it), whereas adults who develop strabismus normally do not suppress and therefore suffer from double vision (diplopia). This also means that adults (and older children) have a higher risk of post-operative diplopia after undergoing strabismus surgery than young children. Patients who have undergone strabismus surgery at a young age often have monofixation syndrome (with peripheral binocular fusion and a central suppression scotoma).

According to a Cochrane review of 2012, controversies remain regarding type of surgery, non-surgical intervention and age of intervention.

The aims of treatment are as follows:

The elimination of any amblyopia

A cosmetically acceptable ocular alignment

long term stability of eye position

binocular cooperation.

A comprehensive eye examination including an ocular motility (i.e., eye movement) evaluation and an evaluation of the internal ocular structures will allow an eye doctor to accurately diagnose the exotropia. Although glasses and/or patching therapy, exercises, or prisms may reduce or help control the outward-turning eye in some children, surgery is often required.

There is a common form of exotropia known as "convergence insufficiency" that responds well to orthoptic vision therapy including exercises. This disorder is characterized by an inability of the eyes to work together when used for near viewing, such as reading. Instead of the eyes focusing together on the near object, one deviates outward.

"Consecutive exotropia" is an exotropia that arises after an initial esotropia. Most often it results from surgical overcorrection of the initial esotropia. It can be addressed with further surgery or with vision therapy; vision therapy has shown promising results if the consecutive exotropia is intermittent, alternating and of small magnitude. (Consecutive exotropia may however also spontaneously develop from esotropia, without surgery or botulinum toxin treatment.)

Because of the risks of surgery, and because about 35% of people require at least one more surgery, many people try vision therapy first. This consists of visual exercises. Although vision therapy is generally not covered by American health insurance companies, many large insurers such as Aetna have recently begun offering full or partial coverage in response to recent studies.

Strabismus surgery is sometimes recommended if the exotropia is present for more than half of each day or if the frequency is increasing over time. It is also indicated if a child has significant exotropia when reading or viewing near objects or if there is evidence that the eyes are losing their ability to work as a single unit (binocular vision). If none of these criteria are met, surgery may be postponed pending simple observation with or without some form of eyeglass and/or patching therapy. In very mild cases, there is a chance that the exotropia will diminish with time. The long-term success of surgical treatment for conditions such as intermittent exotropia is not well proven, and surgery can often result in a worsening of symptoms due to overcorrection. Evidence from the available literature suggests that unilateral surgery was more effective than bilateral surgery for individuals affected with intermittent exotropia.

The surgical procedure for the correction of exotropia involves making a small incision in the tissue covering the eye in order to reach the eye muscles. The appropriate muscles are then repositioned in order to allow the eye to move properly. The procedure is usually done under general anesthesia. Recovery time is rapid, and most people are able to resume normal activities within a few days. Following surgery, corrective eyeglasses may be needed and, in many cases, further surgery is required later to keep the eyes straight.

When a child requires surgery, the procedure is usually performed before the child attains school age. This is easier for the child and gives the eyes a better chance to work together. As with all surgery, there are some risks. However, strabismus surgery is usually a safe and effective treatment.

Treatment is done by changing the optical magnification properties of the auxiliary optics (corrective lenses). The optical magnification properties of spectacle lenses can be adjusted by changing parameters like the base curve, vertex distance, and center thickness. Contact lenses may also provide a better optical magnification to reduce the difference in image size. The difference in magnification can also be eliminated by a combination of contact lenses and glasses (creating a weak telescope system). The optimum design solution will depend on different parameters like cost, cosmetic implications, and if the patient can tolerate wearing a contact lens.

Note however that before the optics can be designed, first the aniseikonia should be known=measured. When the image disparity is astigmatic (cylindrical) and not uniform, images can appear wider, taller, or diagonally different. When the disparity appears to vary across the visual field (field-dependent aniseikonia), as may be the case with an epiretinal membrane or retinal detachment, the aniseikonia cannot fully be corrected with traditional optical techniques like standard corrective lenses. However, partial correction often improves the patient's vision comfort significantly. Little is known yet about the possibilities of using surgical intervention to correct aniseikonia.

It is essential that a child with strabismus is presented to the ophthalmologist as early as possible for diagnosis and treatment in order to allow best possible monocular and binocular vision to develop. Initially, the patient will have a full eye examination to identify any associated pathology, and any glasses required to optimise acuity will be prescribed – although infantile esotropia is not typically associated with refractive error. Studies have found that approximately 15% of infantile esotropia patients have accommodative esotropia. For these patients, antiaccommodative therapy (with spectacles) is indicated before any surgery as antiaccommodative therapy fully corrects their esotropia in many cases and significantly decreases their deviation angle in others.

Amblyopia will be treated via occlusion treatment (using patching or atropine drops) of the non-squinting eye with the aim of achieving full alternation of fixation. Management thereafter will be surgical. As alternative to surgery, also botulinum toxin therapy has been used in children with infantile esotropia. Furthermore, as accompaniment to ophtalmologic treatment, craniosacral therapy may be performed in order to relieve tension ("see also:" Management of strabismus).

When this magnification difference becomes excessive the effect can cause diplopia, suppression, disorientation, eyestrain, headache, and dizziness and balance disorders.

Esotropia is a form of strabismus in which one or both eyes turns inward. The condition can be constantly present, or occur intermittently, and can give the affected individual a "cross-eyed" appearance. It is the opposite of exotropia and usually involves more severe axis deviation than esophoria. Esotropia is sometimes erroneously called "lazy eye", which describes the condition of amblyopia—a reduction in vision of one or both eyes that is not the result of any pathology of the eye and cannot be resolved by the use of corrective lenses. Amblyopia can, however, arise as a result of esotropia occurring in childhood: In order to relieve symptoms of diplopia or double vision, the child's brain will ignore or "suppress" the image from the esotropic eye, which when allowed to continue untreated will lead to the development of amblyopia. Treatment options for esotropia include glasses to correct refractive errors (see accommodative esotropia below), the use of prisms and/or orthoptic exercises and/or eye muscle surgery. The term is from Greek "eso" meaning "inward" and "trope" meaning "a turning".

Management of this condition is surgical and typically involves reducing the strength of the superior rectus muscle or anterior transposition of the inferior oblique muscle of the affected eyes.

Several different surgical procedures exist for the correction of DVD including: inferior oblique anteriorization, inferior oblique anteriorization plus resection, superior rectus recession, superior rectus recession plus posterior fixation suture, and inferior oblique myectomy, though there is insufficient evidence to determine which procedure results in the best outcomes for patients.

Convergence insufficiency may be treated with convergence exercises prescribed by an eyecare specialist trained in orthoptics or binocular vision anomalies. Some cases of convergence insufficiency are successfully managed by prescription of eyeglasses, sometimes with therapeutic prisms.

Pencil push-ups therapy is performed at home. Patient brings a pencil slowly to within 2–3 cm of the eye just above the nose about 15 minutes per day 5 times per week. Patients should record the closest distance that they could maintain fusion (keep the pencil from going double as long as possible) after each 5 minutes of therapy. Computer software may be used at home or in an orthoptists/vision therapists office to treat convergence insufficiency. A weekly 60-minute in-office therapy visit may be prescribed. This is generally accompanied with additional in home therapy.

In 2005, the Convergence Insufficiency Treatment Trial (CITT) published two randomized clinical studies. The first, published in Archives of Ophthalmology demonstrated that computer exercises when combined with office based vision therapy/orthoptics were more effective than "pencil pushups" or computer exercises alone for convergency insufficiency in 9- to 18-year-old children. The second found similar results for adults 19 to 30 years of age. In a bibliographic review of 2010, the CITT confirmed their view that office-based accommodative/vergence therapy is the most effective treatment of convergence insufficiency, and that substituting it in entirety or in part with other eye training approaches such as home-based therapy may offer advantages in cost but not in outcome. A later study of 2012 confirmed that orthoptic exercises led to longstanding improvements of the asthenopic symptoms of convergence sufficiency both in adults and in children. A 2011 Cochrane Review reaffirmed that office-based therapy is more effective than home-based therapy, though the evidence of effectiveness is a lot stronger for children than for the adult population.

Both positive fusional vergence (PFV) and negative fusional vergence (NFV) can be trained, and vergence training should normally include both.

Surgical correction options are also available, but the decision to proceed with surgery should be made with caution as convergence insufficiency generally does not improve with surgery. Bilateral medial rectus resection is the preferred type of surgery. However, the patient should be warned about the possibility of uncrossed diplopia at distance fixation after surgery. This typically resolves within 1–3 months postoperatively. The exophoria at near often recurs after several years, although most patients remain asymptomatic.

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".

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.

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

Dissociated vertical deviation (DVD) is an eye condition which occurs in association with a squint, typically infantile esotropia. The exact cause is unknown, although it is logical to assume it is from faulty innervation of eye muscles.

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.

Esophoria is an eye condition involving inward deviation of the eye, usually due to extra-ocular muscle imbalance. It is a type of heterophoria.

Causes include:

- Refractive errors

- Divergence insufficiency

- Convergence excess; this can be due to nerve, muscle, congenital or mechanical anomalies.

Unlike esotropia, fusion is possible and therefore diplopia is uncommon.

There is no definite treatment.

Because syphilis may be an underlying cause, it should be treated.

Treatment includes penicillin g benzathine 2.4mU IM as a single dose

Or Doxycycline (100 mg PO aid)for those being allergic to penicillin.

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.

A rostral lesion within the midbrain may affect the convergence center thus causing bilateral divergence of the eyes which is known as the WEBINO syndrome (Wall Eyed Bilateral INO) as each eye looks at the opposite "wall".

If the lesion affects the PPRF (or the abducens nucleus) and the MLF on the same side (the MLF having crossed from the opposite side), then the "one and a half syndrome" occurs which, simply put, involves paralysis of all conjugate horizontal eye movements other than abduction of the eye on the opposite side to the lesion.

A spasm of accommodation (also known as a ciliary spasm, an accommodation, or accommodative spasm) is a condition in which the ciliary muscle of the eye remains in a constant state of contraction. Normal accommodation allows the eye to "accommodate" for near-vision. However in a state of perpetual contraction, the ciliary muscle cannot relax when viewing distant objects. This causes vision to blur when attempting to view objects from a distance. This may cause pseudomyopia or latent hyperopia.

Although antimuscarinic drops (homoatropine 5%) can be applied topically to relax the muscle, this leaves the individual without any accommodation and, depending on refractive error, unable to see well at near distances. Also, excessive pupil dilation may occur as an unwanted side effect. This dilation may pose a problem since a larger pupil is less efficient at focusing light (see pupil, aperture, and optical aberration for more.)

Patients who have accommodative spasm may benefit from being given glasses or contacts that account for the problem or by using vision therapy techniques to regain control of the accommodative system..

Possible clinical findings include:

Normal Amplitude of accommodation and Near point of convergence

Reduced Negative relative accommodation

Difficulty clearing plus on facility testing