paralytic strabismus

WordNet

1. affected with paralysis (同)paralyzed
2. a person suffering from paralysis
3. relating to or of the nature of paralysis; "paralytic symptoms" (同)paralytical
4. abnormal alignment of one or both eyes (同)squint

PrepTutorEJDIC

1. 麻痺した,中風の;《英話》泥酔した / 〈C〉中風患者
2. 斜視,やぶにらみ

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/04/06 03:04:10」(JST)

wiki en

[Wiki en表示]

For the protein Strabismus, see Strabismus (protein).

Strabismus
Classification and external resources
Strabismus prevents the eyes from aiming at the same point in space
ICD-10	H49 – H50
ICD-9	378
OMIM	185100
DiseasesDB	29577
MedlinePlus	001004
MeSH	D013285

Strabismus (/strəˈbɪzməs/, from Greek strabismós), also known as heterotropia, is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and thus hampers proper binocular vision, and which may adversely affect depth perception. Strabismus is primarily managed by ophthalmologists, optometrists and orthoptists. Strabismus is present in about 4% of children. Treatment should be started as soon as possible to ensure the development of the best possible visual acuity and stereopsis.

Classification

Strabismus is classified as manifest or latent. A manifest deviation, or heterotropia, is present while the patient views a target binocularly, with no occlusion of either eye. The patient is unable to align the gaze of each eye to achieve fusion. A latent deviation, or heterophoria, is only present after binocular vision has been interrupted, typically by covering one eye. This type of patient can typically maintain fusion despite the misalignment that occurs when the positioning system is relaxed. Intermittent strabismus is a combination of both of these types, where the patient can achieve fusion, but occasionally or frequently falters to the point of a manifest deviation.

Strabismus may also be classified as unilateral if the one eye consistently deviates, or alternating if either of the eyes can be seen to deviate. Alternation of the strabismus may occur spontaneously, with or without subjective awareness of the alternation. Alternation may also be triggered by various tests during an eye exam.

Horizontal deviations are classified into two varieties. Eso- describes inward or convergent deviations. Exo- describes outward or divergent misalignment. Hyper- is the term for an eye whose gaze is directed higher than the fellow eye while hypo- refers to an eye whose gaze is directed lower. Torsional strabismus occurs when the eyes rotate around the anterior-posterior axis to become misaligned, which is quite rare.

These prefixes are combined with -tropia and -phoria to describe various types of strabismus. For example, a constant left hypertropia exists when a patient's left eye is aimed higher than the right. A patient with an intermittent right esotropia has a right eye that occasionally drifts toward their nose, but at other times is able to align their eyes together. A patient with a mild exophoria can maintain fusion during normal circumstances, but when the system is disrupted, the relaxed posture of their eyes is slightly divergent.

Strabismus can be further classified as follows:

• Paretic strabismus is due to paralysis of one or several extraocular muscles.
• Non-paretic strabismus is not due to paralysis of extraocular muscles.
• Comitant strabismus is a deviation that is the same magnitude regardless of gaze position.
• Non-comitant strabismus has a magnitude that varies as the patient shifts their gaze up, down, or to the sides.

Non-paretic strabismus is generally concomitant. Paretic strabismus can be either comitant or non-comitant.

Pseudo-strabismus is a condition when a person's eye appears misaligned but further testing shows normal binocular vision. For example, patients, especially infants, with prominent epicanthal folds can appear to have an esotropia due to less sclera being visible nasally.

Signs and symptoms

Aligned vergence; how one ideally views objects

Esotropia

Exotropia

Arrow/dotted line indicates fixation distance. All three patients are fixating with their right eye (assuming an overhead view).

When observing a patient with strabismus, the misalignment of their eyes may be quite apparent. A patient with a constant eye turn of significant magnitude is very easy to notice. However, a small magnitude or intermittent strabismus can easily be missed upon casual observation. In any case, an eye care professional can conduct various tests, such as cover testing, to determine the full extent of the strabismus.

Symptoms of strabismus include double vision and/or eye strain. To avoid double vision, the brain may adapt by ignoring one eye. In this case, there is often no noticeable symptoms other than a minor loss of depth perception.

Pathophysiology

Strabismus can be caused when the cranial nerves III (oculomotor), IV (trochlear), or VI (abducens) have a lesion. A strabismus caused by a lesion in either of these nerves results in the lack of innervation to eye muscles and results in a change of eye position. A strabismus may be a sign of increased intracranial pressure, as CN VI is particularly vulnerable to damage from brain swelling, as it runs between the clivus and Brain stem. The primary sign of strabismus is a visible misalignment of the eyes, with one eye turning in, out, up, down or at an oblique angle.

Recent evidence indicates that a cause for infantile strabismus may lie with the input that is provided to the visual cortex.

When the misalignment of the eyes is large and obvious, the strabismus is called "large-angle," referring to the angle of deviation between the line of sight of the straight eye and that of the misaligned eye. Less obvious eye turns are called small-angle strabismus.

Typically, constant large-angle strabismus does not cause symptoms such as eye strain and headaches because there is virtually no attempt by the brain to straighten the eyes. Because of this, large-angle strabismus usually causes severe amblyopia in the turned eye if left untreated.

In most cases, the only effective treatment for a constant eye turn is strabismus surgery. Esotropia (crossed eyes) needs to be treated early in life to prevent amblyopia.

Less noticeable cases of small-angle strabismus are more likely to cause disruptive visual symptoms, especially if the strabismus is intermittent or alternating. In addition to headaches and eye strain, symptoms may include an inability to read comfortably, fatigue when reading and unstable or "jittery" vision. If small-angle strabismus is constant and unilateral, it can lead to significant amblyopia in the misaligned eye.

Psychosocial effects

Both large-angle and small-angle strabismus can be psychologically damaging and affect the self-esteem of children and adults with the condition, as it interferes with normal eye contact with others, often causing embarrassment, anger, and awkwardness.

School children, teenagers and adults may experience psychosocial difficulties if they have noticeable strabismus.A study showed that adults and children perceive a squinting right eye as more distubing than a squinting left eye, and that children perceive an inward squint (esotropia) as worse than an outward squint (exotropia).

Successful surgical correction of strabismus is known to have positive effects on psychological well-being, also when it is performed at an adult age.

See also: Stereopsis#Prevalence and impact

Diagnosis

During eye examination, a test which is called cover test, is typically used in the diagnosis and measurement of strabismus. If the eye being tested is the strabismic eye, then it will fixate on the object after the "straight" eye is covered, as long as the vision in this eye is good enough. If the "straight" eye is being tested, there will be no change in fixation, as it is already fixated. Depending on the direction that the strabismic eye deviates, the direction of deviation may be assessed. Exotropic is outwards (away from the midline) and esotropic is inwards (towards the nose); these are types of horizontal strabismus. "Hypertropia" is upward, and "Hypotropia" is downward; these are types of vertical strabismus, which are less common.

A simple screening test for strabismus is the Hirschberg test. A flashlight is shone in the patient's eye. When the patient is looking at the light, a reflection can be seen on the front surface of the pupil. If the eyes are properly aligned with one another, then the reflection will be in the same spot of each eye. Therefore, if the reflection is not in the same place in each eye, then the eyes are not properly aligned.

Laterality

Strabismus may be classified as unilateral if the one eye consistently deviates, or alternating if either of the eyes can be seen to deviate. Alternation of the strabismus may occur spontaneously, with or without subjective awareness of the alternation. Alternation may also be seen following the cover test, with the previously examined eye remaining straight while the previously straight eye is now seen to be deviated on removal of the cover. The cover-uncover test is used to diagnose the type of strabismus (also known as tropia) present.

Onset

Strabismus may also be classified based on time of onset, either congenital, acquired, or secondary to another pathological process, such as cataract. Many infants are born with their eyes slightly misaligned. The best time for physicians to assess this is between ages 3 and 6 months.

Differential diagnosis

Pseudostrabismus is the false appearance of strabismus. It generally occurs in infants and toddlers whose bridge of the nose is wide and flat, causing the appearance of strabismus. With age, the bridge of the child's nose narrows and the folds in the corner of the eyes go away. To detect the difference between pseudostrabismus and strabismus, a Hirschberg test may be used.

Convergence insufficiency, "the inability to maintain binocular function (keeping the two eyes working together) while working at a near distance," "can often be treated by practicing convergence through exercises."

Management

Surgery to correct strabismus on an eight-month-old infant

As with other binocular vision disorders, the primary therapeutic goal for those with strabismus is comfortable, single, clear, normal binocular vision at all distances and directions of gaze.

Whereas amblyopia (lazy eye), if minor and detected early, can often be corrected with use of an eye patch on the dominant eye and/or vision therapy, the use of eye patches is unlikely to change the angle of strabismus. Strabismus is usually treated with a combination of eyeglasses, vision therapy, and surgery, depending on the underlying reason for the misalignment. Surgery does not change the vision^{[citation needed]}; it attempts to align the eyes by shortening, lengthening, or changing the position of one or more of the extraocular eye muscles and is frequently the only way to achieve cosmetic improvement and restoring^{[citation needed]} binocular vision. The procedure can typically be performed in about an hour, and requires about one or two weeks for recovery. Adjustable sutures may be used to permit refinement of the eye alignment in the early postoperative period.

Double vision can rarely result, especially immediately after the surgery,^{[citation needed]} and vision loss is very rare. Glasses affect the position by changing the person's reaction to focusing. Prisms change the way light, and therefore images, strike the eye, simulating a change in the eye position.

Early treatment of strabismus in infancy may reduce the chance of developing amblyopia and depth perception problems. Most children eventually recover from amblyopia if they have had the benefit of patches and corrective glasses. It has long been considered that amblyopia remains permanent if not treated within a critical period, namely before the age of about 7 years; however, recent discoveries give reason to challenge this view and to adapt the earlier notion of a critical period to account for stereopsis recovery in adults.

Eyes that remain misaligned can still develop visual problems. Although not a cure for strabismus, prism lenses can also be used to provide some temporary comfort for sufferers and to prevent double vision from occurring.

Botulinum Toxin type A (BT-A) was approved to treat strabismus by the Food and Drug Administration in 1989. Most commonly used in adults, the toxin is injected in the stronger muscle, causing temporary paralysis. The treatment may need to be repeated 3–4 months later once the paralysis wears off. Common side effects are double vision, droopy eyelid, over correction and no effect. The side effects will resolve fairly quickly.

In adults with previously normal alignment, the onset of strabismus usually results in double vision or diplopia.

Prognosis

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 that 85% of adult strabismus patients "reported that they had problems with work, school, and sports because of their strabismus". The same study also reported that 70% said strabismus "had a negative effect on their self-image". It is possible that after surgery the squint returns again, therefore, a second operation is sometimes required to straighten the eyes.

See also

• Amblyopia
• Strabismus surgery
• Pediatric ophthalmology
• Retinoblastoma
• Palsy of cranial nerve III (oculomotor), IV (trochlear), VI (abducens)
• Orthoptics
• Bates method
• Duane syndrome
• Convergence insufficiency

References

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

• 1. 小児における斜視の評価およびマネージメント evaluation and management of strabismus in children
• 2. 小児における第4脳神経（滑車神経）麻痺 fourth cranial nerve trochlear nerve palsy in children
• 3. 小児における水平斜視の原因 causes of horizontal strabismus in children
• 4. 小児における垂直斜視の原因 causes of vertical strabismus in children
• 5. 小児期の限局性強皮症 localized scleroderma in childhood

English Journal

• Incidence, types, and lifetime risk of adult-onset strabismus.

• Martinez-Thompson JM1, Diehl NN2, Holmes JM3, Mohney BG4.
• Ophthalmology.Ophthalmology.2014 Apr;121(4):877-82. doi: 10.1016/j.ophtha.2013.10.030. Epub 2013 Dec 8.
• OBJECTIVE: To describe the incidence and types of adult-onset strabismus in a geographically defined population.DESIGN: Retrospectively reviewed population-based cohort.PARTICIPANTS: All adult (≥19 years of age) residents of Olmsted County, Minnesota, diagnosed with new-onset adult strabismus from
• PMID 24321142

• Treatment of consecutive exotropia: unilateral lateral rectus recession combined with medial rectus advancement or resection.

• Mangla D, Simon JW, Mangla N, Zobal-Ratner J.
• Journal of pediatric ophthalmology and strabismus.J Pediatr Ophthalmol Strabismus.2014 Mar-Apr;51(2):116-9. doi: 10.3928/01913913-20140205-03. Epub 2014 Feb 12.
• PURPOSE: Consecutive exotropia presents a difficult clinical problem, especially when previously recessed medial recti are to be strengthened. Surgical options include advancement, typically with a small resection, and resection alone.METHODS: The authors retrospectively reviewed records of all pati
• PMID 24512646

• Lateral rectus superior compartment palsy.

• Clark RA1, Demer JL2.
• American journal of ophthalmology.Am J Ophthalmol.2014 Feb;157(2):479-487.e2. doi: 10.1016/j.ajo.2013.09.027. Epub 2013 Sep 29.
• PURPOSE: To employ magnetic resonance imaging (MRI) to seek evidence of compartmental lateral rectus atrophy consistent with a lesion involving selective denervation of only 1 of the 2 neuromuscular compartments of the lateral rectus.DESIGN: Prospective observational case-control series.METHODS: At
• PMID 24315033

Japanese Journal

• 学術展示 脳幹部病変による眼球偏位に対する斜視手術 (第68回日本弱視斜視学会(3))

• 大木 玲子,本村 由香,岸 大地 [他]
• 眼科臨床紀要 6(3), 219-222, 2013
• NAID 40019617317

• 開散麻痺の手術

• 丸尾 敏之,久保田 伸枝,丸尾 敏夫
• 眼科臨床紀要 5(4), 322-325, 2012
• NAID 40019293668

• シンポジウム「麻痺性斜視治療の可能性と限界」 麻痺性斜視の一般的手術法 (第67回日本弱視斜視学会(1))

• 林 孝雄
• 眼科臨床紀要 5(1), 33-37, 2012
• NAID 40019184971

Related Links

• Paralytic strabismus - Medical Dictionary - The Free Dictionary

encyclopedia ? strabismus. (redirected from Paralytic strabismus). Also found in: Dictionary/thesaurus, Encyclopedia, Wikipedia, 0.01 sec. Strabismus. Definition. Strabismus is a condition in which the eyes do not point in the same direction.

Related Pictures

---

★リンクテーブル★

関連記事	「paralytic」

「paralytic」

　　[★]

• 麻痺性の