What is Strabismus?

Squint refers to the fact that both eyes cannot look at the target at the same time. It belongs to extraocular muscle disease and can be divided into two categories: common strabismus and paralytic strabismus. Common strabismus is characterized by no dyskinesias of the eyeballs, and the same degree of strabismus in the first and second eyes. Paralytic strabismus has restricted eye movements, and diplopia can be congenital or caused by trauma or Caused by systemic diseases.

Basic Information

nickname: Squint
English name: strabismus
Visiting department: Ophthalmology

Multiple groups: Toddler
Common locations: eye
Common causes: Heredity, decreased intraocular rectus muscle tension, unbalanced eye muscle strength, etc.
Common symptoms: Esotropia, exotropia, up and down

Causes of strabismus

Regulation theory

The accommodative effect of the eye and the collective effect of the eye are interrelated, and certain adjustments bring corresponding sets. Often due to the regulation-collective reflexes that are too strong, the role of the medial rectus tends to exceed that of the external rectus, thus forming a common esotropia. Myopia is used with little or no adjustment when looking at near targets. At the same time, the collective force is weakened, so the tension of the medial rectus muscle is reduced, and sometimes common exotropia is formed.

2. Binocular reflex theory

Binocular monoopia is a conditional reflex, which is accomplished by the fusion function, which is acquired the day after tomorrow. If the visual acuity of the two eyes is different during the formation of the conditioned reflex, the visual sensation in one eye is impaired due to the obvious sensation or movement disorder, which will result in a separation state of the eyes, that is, strabismus.

3. Anatomy

Excessive or incomplete development of an extraocular muscle, abnormal attachment of extraocular muscles, orbital development, abnormalities in the orbital fascia structure, etc., can lead to unbalanced muscle strength and strabismus.

4. Genetics

It is common in clinical practice that many people in the same family have common strabismus, which may be related to genetic factors.

Clinical manifestations of strabismus

Patients with strabismus, because the eye position is not correct, when they pay attention to an object, the image of this object falls on the central fovea of the retina in the normal eye, and the strabismus eye falls outside the fovea, so that the subject will have double vision; Suppressed, loss of single vision and three-dimensional vision in both eyes, and some may cause poor vision development and amblyopia.

Esotropia

Eye position is deflected inward. People born to within are called congenital esotropia. The deflection angle is usually large. Acquired esotropia is divided into accommodative and non-accommodative. Acoustic esotropia usually occurs in children 2 to 3 years old. Children usually have high and middle hyperopia, or abnormally regulate cohesion and adjustment ratio.

2. Exotropia

The position of the eye is outwardly deviated. Generally, it can be divided into intermittent and constant exotropia. Intermittent exotropia is due to the patient's better ability to fuse images. Most of the time the eye position can be maintained in the normal position by fusion ability. Only when occasionally in the sun or fatigue and distracted, will show exotropia. Some children also appear to close one eye in the strongest sunlight. Intermittent exotropia often develops into constant exotropia.

3. Squint up and down

The eye position is skewed upward or downward, which is less common than esotropia and exotropia. Up and down strabismus is often accompanied by head skew, which is compensatory head position.

Strabismus examination

Here are the routine tests for strabismus:

1. Examination of binocular vision

(1) Synovial machines are commonly used in China to check the third level of binocular vision.

(2) Quantitative measurement of the stereoscopic function. The stereoscopic sharpness was measured by the stereoscopic quantitative picture of the synoptic machine or the stereogram of Yan's random point.

2. Refractive examination

Atropine paralysis ciliary muscle optometry: understand the relationship between amblyopia and strabismus and refractive.

3. Measurement of eye position and oblique viewing angle

Determine what type of strabismus. The size of the oblique view must be checked for surgical design.

4. Eye movement check

Determine the function of the extraocular muscles to see if eye movements are in place.

5. Is there a compensation position?

Help diagnose which paralysis of the extraocular muscles.

6. Examination to determine paralysis

Check the motor function of the eyeball, fixation of the eyes separately, and the angle of strabismus of fixation in each direction of the single eye.

Checks such as the Hess screen method can help determine.

7. Pull test

(1) Preoperative assessment After the eyeball is pulled to the right position before surgery, the postoperative diplopia and patient tolerance are estimated.

(2) Passive traction test can understand the presence or absence of mechanical distraction or muscle spasm of extraocular muscles.

(3) Active contraction test to understand muscle function.

8. Oblique inspection

Quantitative determinations were performed using a crypto oblique meter. Collection of near-point detection: help diagnose muscular visual fatigue.

9. Determination of the ratio of regulatory set / adjustment (AC / A)

Helps judge the relationship between strabismus and accommodation.

Strabismus diagnosis

Diagnosis can be made in the following ways:

1. Ask a medical history

Ask the patient's age in detail, the exact time of onset, the cause or cause of the onset, the development of strabismus, what treatments have been performed, and whether they have a family history.

2. Eye appearance inspection

Pay attention to the direction and extent of the patient's eye position deviation, whether the eyelid fissure is equal, whether the face is symmetrical, and whether there is a compensatory head position.

3. Vision test and refractive test

Check the patient's far and near vision and correct vision. For patients with high myopia and astigmatism, and adolescents, a refractive examination must be performed after dilation.

4. Covering test

Concealment tests can be used to perform qualitative inspections of strabismus simply and accurately.

5. Check eye movements

Observe the six main movement directions to determine if there is any abnormality in the function of each eye muscle.

6.Oblique viewing

The oblique view is divided into a first oblique view and a second oblique view. When oblique fixation, the oblique angle is called the first oblique angle; when oblique fixation, the oblique angle is called the second oblique angle. Measuring the oblique angles of the first and second oblique viewing angles can assist in the diagnosis of paralyzed eyes. The commonly used clinical methods for quantitatively measuring oblique viewing angles are: corneal reflection method, synoptic inspection method, triangular prism and covering method.

7. Other

In addition, there are oblique view measurement, oblique view method, Markov rod plus triangular prism inspection method, perimeter measurement method and so on.

Strabismus complications

Most patients with strabismus have weakened or lost stereo vision, amblyopia may occur in those with monocular suppression, and diplopia and confusion in some patients.

Strabismus treatment

Non-surgical treatment

The treatment of strabismus is aimed first at amblyopia to promote good vision development in both eyes, and secondly at the correct position of the deviated eye. The treatment methods for strabismus include: wearing glasses, covering with eye masks, and orthographic training. Wearing goggles is the main method for treating amblyopia caused by strabismus. Ocular muscle surgery involves relaxing (weakening) or shortening (enhancing) one or more muscles in the extraocular muscles of one or both eyes. Mild strabismus can be corrected with a prism. Orthotopic training can be used as a supplement before and after surgery.

2. Surgical treatment

The younger the age of strabismus treatment, the better the treatment. Strabismus surgery is not only to correct the position of the eye and improve the appearance, but also to establish binocular vision. The best time for surgery is before 6 to 7 years old. Postoperative binocular vision training is used to enhance and maintain stable stereoscopic function.