Most patients are diagnosed by the age of 10 years and Duane's is more common in girls (60 percent of the cases) than boys (40 percent of the cases). A French study reports that this syndrome accounts for 1.9% of the population of strabismic patients, 53.5% of patients are female, is unilateral in 78% of cases, and the left eye (71.9%) is affected more frequently than the right. Around 10–20% of cases are familial; these are more likely to be bilateral than non-familial Duane syndrome. Duane syndrome has no particular race predilection.

The gene sal-like 4 (SALL4) or CHN1 ("chimerin") has became a mutated gene (protein) and it is also one of the cause of the body's Duane Syndrome.

In Brown's original series there was a 3:2 predominance of women to men and nearly twice as many cases involved the right eye as the left. 10% of cases showed bilaterality. Familial occurrence of Brown's syndrome has been reported.

Brown's syndrome is a rare form of strabismus characterized by limited elevation of the affected eye. The disorder may be congenital (existing at or before birth), or acquired. Brown syndrome is caused by a malfunction of the Superior oblique muscle, causing the eye to have difficulty moving up, particularly during adduction (when eye turns towards the nose). Harold W. Brown first described the disorder in 1950 and initially named it the "superior oblique tendon sheath syndrome".

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 may be either paretic, restrictive (fibrosis) or overactive effect of the muscles. Congenital cases may have developmental abnormality due to abnormal muscle structure, usually muscle atrophy / hypertrophy or rarely, absence of the muscle and incorrect placement.

Specific & common causes include:

- Superior oblique Palsy / Congenital fourth nerve palsy

- Inferior oblique overaction

- Brown's syndrome

- Duane's retraction syndrome

- Double elevator palsy

- Fibrosis of rectus muscle in Graves Disease (most commonly inferior rectus is involved)

- Surgical trauma to the vertical muscles (e.g. during scleral buckling surgery or cataract surgery causing iatrogenic trauma to the vertical muscles).

Sudden onset hypertropia in a middle aged or elderly adult may be due to compression of the trochlear nerve and mass effect from a tumor, requiring urgent brain imaging using MRI to localise any space occupying lesion. It could also be due to infarction of blood vessels supplying the nerve, due to diabetes and atherosclerosis. In other instances it may be due to an abnormality of neuromuscular transmission, i.e., Myasthenia Gravis.

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.

The eye findings of Parinaud's Syndrome generally improve slowly over months, especially with resolution of the causative factor; continued resolution after the first 3–6 months of onset is uncommon. However, rapid resolution after normalization of intracranial pressure following placement of a ventriculoperitoneal shunt has been reported.

Treatment is primarily directed towards etiology of the dorsal midbrain syndrome. A thorough workup, including neuroimaging is essential to rule out anatomic lesions or other causes of this syndrome. Visually significant upgaze palsy can be relieved with bilateral inferior rectus recessions. Retraction nystagmus and convergence movement are usually improved with this procedure as well.

Parinaud's Syndrome results from injury, either direct or compressive, to the dorsal midbrain. Specifically, compression or ischemic damage of the mesencephalic tectum, including the superior colliculus adjacent oculomotor (origin of cranial nerve III) and Edinger-Westphal nuclei, causing dysfunction to the motor function of the eye.

Classically, it has been associated with three major groups:

1. Young patients with brain tumors in the pineal gland or midbrain: pinealoma (intracranial germinomas) are the most common lesion producing this syndrome.

2. Women in their 20s-30s with multiple sclerosis

3. Older patients following stroke of the upper brainstem

However, any other compression, ischemia or damage to this region can produce these phenomena: obstructive hydrocephalus, midbrain hemorrhage, cerebral arteriovenous malformation, trauma and brainstem toxoplasmosis infection. Neoplasms and giant aneurysms of the posterior fossa have also been associated with the midbrain syndrome.

Vertical supranuclear ophthalmoplegia has also been associated with metabolic disorders, such as Niemann-Pick disease, Wilson's disease, kernicterus, and barbiturate overdose.

Refractive errors such as hyperopia and Anisometropia may be associated abnormalities found in patients with vertical strabismus.

The vertical miscoordination between the two eyes may lead to

- Strabismic amblyopia, (due to deprivation / suppression of the deviating eye)

- cosmetic defect (most noticed by parents of a young child and in photographs)

- Face turn, depending on presence of binocular vision in a particular gaze

- diplopia or double vision - more seen in adults (maturity / plasticity of neural pathways) and suppression mechanisms of the brain in sorting out the images from the two eyes.

- cyclotropia, a cyclotorsional deviation of the eyes (rotation around the visual axis), particularly when the root cause is an oblique muscle paresis causing the hypertropia.

Duane-radial ray syndrome is caused by mutations in the "SALL4" gene which is a part of a group of genes called the SALL family. This gene plays an important role in embryonic development by providing instructions to make proteins that are involved in the formation of tissues and organs. SALL proteins act as transcription factors in that they attach themselves to certain regions in DNA in order to help control certain gene activities. Due to the mutations in the "SALL4" gene, proteins can not be made because one copy of the gene in each cell is stopped from performing its duty. These mutations are heterozygous and can be nonsense, short duplications, or deletions. At this time, there is no clear reason as to why a reduced amount of the SALL4 protein causes the symptoms of Duane-radial ray syndrome and similar conditions.

Duane-radial ray syndrome is inherited through autosomal dominance meaning that a mutation in one copy of the SALL 4 gene is all it takes to cause this syndrome. Those with this condition can have affected parents, but it can also manifest for the first time with no family history which is called de novo. Since Duane-radial ray syndrome is an autosomal dominant disorder, there is a 50% chance of passing the mutation on to offspring.

Von Graefe's sign is the lagging of the upper eyelid on downward rotation of the eye, indicating exophthalmic goiter (Graves' Disease). It is a dynamic sign, whereas lid lag is a static sign which may also be present in cicatricial eyelid retraction or congenital ptosis.

A pseudo Graefe's sign (pseudo lid lag) shows a similar lag, but is due to aberrant regeneration of fibres of the oculomotor nerve (III) into the elevator of the upper lid. It occurs in paramyotonia congenita.

A pseudo Graefe's sign is most commonly manifested in just one eye but can occasionally be observed in both. The reason only one eye is affected is not yet clear.

Use of high doses of opioid drugs such as morphine, oxycodone, heroin, or hydrocodone can cause ptosis. Pregabalin (Lyrica), an anticonvulsant drug, has also been known to cause mild ptosis.

The mechanism for this disorder is somewhat unclear. What is known is that Duane-radial ray syndrome begins with mutations in the SALL4 gene. Due to these mutations, the proteins involved in embryonic development for making tissues and organs are not functioning properly. These proteins then cause improper development of bones (e.g. absence of the radius), abnormal eye movements, and other miscellaneous symptoms.

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.

Ptosis occurs due to dysfunction of the muscles that raise the eyelid or their nerve supply (oculomotor nerve for levator palpebrae superioris and sympathetic nerves for superior tarsal muscle). It can affect one eye or both eyes and is more common in the elderly, as muscles in the eyelids may begin to deteriorate. One can, however, be born with ptosis. Congenital ptosis is hereditary in three main forms. Causes of congenital ptosis remain unknown. Ptosis may be caused by damage/trauma to the muscle which raises the eyelid, damage to the superior cervical sympathetic ganglion or damage to the nerve (3rd cranial nerve (oculomotor nerve)) which controls this muscle. Such damage could be a sign or symptom of an underlying disease such as diabetes mellitus, a brain tumor, a pancoast tumor (apex of lung) and diseases which may cause weakness in muscles or nerve damage, such as myasthenia gravis or Oculopharyngeal muscular dystrophy. Exposure to the toxins in some snake venoms, such as that of the black mamba, may also cause this effect.

Ptosis can be caused by the aponeurosis of the levator muscle, nerve abnormalities, trauma, inflammation or lesions of the lid or orbit. Dysfunctions of the levators may occur as a result of autoimmune antibodies attacking and eliminating the neurotransmitter.

Ptosis may be due to a myogenic, neurogenic, aponeurotic, mechanical or traumatic cause and it usually occurs isolated, but may be associated with various other conditions, like immunological, degenerative, or hereditary disorders, tumors, or infections

Acquired ptosis is most commonly caused by aponeurotic ptosis. This can occur as a result of senescence, dehiscence or disinsertion of the levator aponeurosis. Moreover, chronic inflammation or intraocular surgery can lead to the same effect. Also, wearing contact lenses for long periods of time is thought to have a certain impact on the development of this condition.

Congenital neurogenic ptosis is believed to be caused by the Horner syndrome. In this case, a mild ptosis may be associated with ipsilateral ptosis, iris and areola hypopigmentation and anhidrosis due to the paresis of the Mueller muscle. Acquired Horner syndrome may result after trauma, neoplastic insult, or even vascular disease.

Ptosis due to trauma can ensue after an eyelid laceration with transection of the upper eyelid elevators or disruption of the neural input.

Other causes of ptosis include eyelid neoplasms, neurofibromas or the cicatrization after inflammation or surgery. Mild ptosis may occur with aging.

A drooping eyelid can be one of the first signals of a third nerve palsy due to a cerebral aneurysm, that otherwise is asymptomatic and referred to as an oculomotor nerve palsy.

Glossoptosis is a medical condition and abnormality which involves the downward displacement or retraction of the tongue. It may cause non-fusion of the hard palate causing cleft palate.

It is one of the features of Pierre Robin sequence and Down syndrome.

Very few risk factors for choanal atresia have been identified. While causes are unknown, both genetic and environmental triggers are suspected. One study suggests that chemicals that act as endocrine disrupters may put an unborn infant at risk. A 2012 epidemiological study looked at atrazine, a commonly used herbicide in the U.S., and found that women who lived in counties in Texas with the highest levels of this chemical being used to treat agricultural crops were 80 times more likely to give birth to infants with choanal atresia or stenosis compared to women who lived in the counties with the lowest levels. Another epidemiological report in 2010 found even higher associations between increased incidents of choanal atresia and exposure to second-hand-smoke, coffee consumption, high maternal zinc and B-12 intake and exposure to anti-infective urinary tract medications.

The prevalence of Klippel–Feil syndrome is unknown due to the fact that there was no study done to determine the true prevalence.

Although the actual occurrence for the KFS syndrome is unknown, it is estimated to occur 1 in 40,000 to 42,000 newborns worldwide. In addition, females seem to be affected slightly more often than males.

Congenital heterochromia is usually inherited as an autosomal dominant trait.

Currently there are only around 26 people in the world that are known to have this rare condition. Inheritance is thought to be X-linked recessive.

Wildervanck syndrome or cervico-oculo-acoustic syndrome comprises a triad of:

- Duane syndrome

- Klippel-Feil anomaly (fused cervical vertebrae)

- congenital hearing loss

Heterochromia has also been observed in those with Duane syndrome.

The prevalence has been estimated at 1 in 10,000 births, but exact values are hard to know because some that have the symptoms rarely have Pierre-Robin sequence (without any other associated malformation).

Almost all cases of synkinesis develop as a sequel to nerve trauma (the exception is when it is congenitally acquired as in Duane-Retraction Syndrome and Marcus Gunn phenomenon). Trauma to the nerve can be induced in cases such as surgical procedures, nerve inflammation, neuroma

, and physical injury.

The heterogeneity of the Klippel–Feil syndrome has made it difficult to outline the diagnosis as well as the prognosis classes for this disease. Because of this, it has complicated the exact explanation of the genetic cause of the syndrome.

The prognosis for most individuals with KFS is good if the disorder is treated early on and appropriately. Activities that can injure the neck should be avoided, as it may contribute to further damage. Other diseases associated with the syndrome can be fatal if not treated, or if found too late to be treatable.