A-V syndrome
Introduction
Introduction to AV syndrome AV syndrome (AandVsyndrome) is a sub-type horizontal strabismus with vertical non-common strabismus (verticalinconcomitancestrabismus), that is, when the upward and downward looking, the horizontal slope changes significantly. And a type of strabismus named after the "A" and "V" letters. basic knowledge The proportion of illness: 0.002% Susceptible people: no special people Mode of infection: non-infectious Complications: strabismus
Cause
Causes of AV syndrome
Urist believes that the formation of the AV sign is related to the difference between the inner and outer rectus muscles in the upward and downward gaze. In the physiological state, when the eyes are gazing upward, the separation effect is slightly increased.
Jampolsky believes that the strength of the superior and inferior oblique muscles is an important reason for the formation of the AV sign. Because the secondary action of the oblique muscles causes the eyeball to turn outward, when the strength of the lower oblique muscle is too strong, it can cause the V phenomenon; When the strength is insufficient, it will cause the phenomenon of A; the strength of the superior oblique muscle is too strong and causes the phenomenon of A; the lack of strength of the superior oblique muscle causes the V phenomenon. In short, the horizontal slope is increased when looking upwards, which is the reason for the lower oblique muscle. Caused by the increase in horizontal inclination when looking down, caused by the upper oblique muscle, von Noorden believes that abnormal function of the oblique muscle is a common cause of AV syndrome, and AV syndrome with abnormal osseous function often causes Rotational strabismus, which produces rotational strabismus from the AV syndrome with abnormal anatomical function. After correction of the horizontal muscle tip tilt, the squint can not be corrected, and this squint is confirmed by fundus photography.
Brown believes that the function of the upper and lower rectus muscles is a cause of the formation of the AV sign. Because these two muscles have a secondary effect on the intraocular rotation, when the superior rectus muscle is too strong, it can cause the A phenomenon; When the strength of the superior rectus muscle is weak, it will cause V phenomenon; when the strength of the inferior rectus muscle is strong, it can cause V phenomenon; the strength of the lower rectus muscle is weaker and cause the phenomenon of A. In short, the difference in horizontal inclination when looking directly at the top is It is caused by the cause of the superior rectus muscle, and the difference in the horizontal slope when looking directly downward is caused by the lower rectus muscle.
Those who hold this opinion believe that the AV sign is caused by abnormalities in both horizontal and vertical muscles, and is not caused by abnormality of one muscle alone. Some patients may be mainly too strong or too weak for horizontal muscles, resulting in Others may be caused by secondary changes in vertical muscles; while others may be predominantly too strong or too weak for vertical muscle function, resulting in secondary changes in horizontal muscles, or changes in both horizontal and vertical muscle functions to form AV signs.
(1) The AV sign is related to the shape of the face: such as the Mongolian-like face (upward movement of the outer crotch) can cause A-inner and V-external; and the anti-Mongolian (Caucasian) face (no change in the outer crotch) A bit or a slight shift) can cause A-outer skew and V-inner skew.
(2) Fascia abnormalities: such as Brown's superior oblique sheath syndrome often combined with V-external oblique, this is due to the lack of elasticity of the superior oblique muscle sheath, resulting in forced abduction during the upturn, in the Johnson adhesion syndrome, may also Produces a mechanical distribution phenomenon when rotating vertically.
(3) abnormal muscle attachment point: Some people think that some patients with V phenomenon have higher attachment points of the medial rectus tendon than normal, and the attachment position of the lateral rectus tendon is lower than normal, and the attachment point moves forward or backward. Caused the AV sign.
Clinically, the AV sign is rarely seen by anatomical factors, but it is more common due to paralysis factors, because it can be seen from the definition of AV sign that it is accompanied by vertical non-common strabismus. Subtype horizontal strabismus, that is to say, regardless of the horizontal slope or vertical slope, the muscles are too strong or too weak, and the vertical rectus and oblique muscles are still inconclusive. It has a role in both vertical muscles, but the two of them are most important and cannot be explained clearly. The vertical muscles have both nerve impulses and mechanical effects, while the horizontal muscles may be more prominent when the muscles are too strong or too weak.
In addition, there is also a physiological V phenomenon, that is, in the case where there is no strabismus in the original eye position, when the eye is gazing upward, an external oblique can be generated (up to 17 ), and when looking downward, an A phenomenon can be generated (up to 5 ). There are many, this may be related to the innervation factor.
The reason for the abnormality of the convergence and fusion function is that when the gaze is downward and the fusion cannot be maintained, the A phenomenon can be generated; when the gaze is not able to maintain the fusion, the V phenomenon can be generated, which is common in the intermittent external oblique.
There are few reports on genetic factors related to AV signs in the genetic factors literature. In China, a case of 11 cases of V-exotropia in 5 generations was reported. It is autosomal dominant, only one case of surgery is performed. Abnormal muscle attachment.
In short, among the above factors, the pathogenesis of all cases cannot be explained by a simple cause, but it is mainly caused by the cause of extraocular muscles.
Prevention
AV syndrome prevention
There is no effective preventive measure for this disease. Early detection and early diagnosis are the key to the prevention and treatment of this disease.
Complication
Complications of AV syndrome Complications
Generally no special complications
Symptom
Symptoms of AV syndrome Common symptoms Internal oblique A sign Eyes gaze upward Mandibular angle Eversion eyeball invagination External oblique A sign External oblique V sign
1. Clinical type and performance
There are many types of AV signs in the literature. Urist divides them into V-internal, A-internal, V-external and A-external 4, and Costenbader adds 4 rare on the basis of Urist classification. The phenomenon of X, Y, , (inverted Y) and (diamond), and then X phenomenon is divided into XA and XV phenomenon.
(1) A-esotropia: also known as esotropia A sign, esotropia Aphenomenon, A-internal, convergent strabismus A syndrome , that is, the number of internal slopes increases when viewed from the top, and the number of internal slopes decreases or even disappears when viewed from the front, and the internal inclination is almost equal when looking far and near, and the upper oblique muscles when turning inward and downward. Excessively strong, the eyeball is invaginated when the eye is closed, and the patient may have a mandible uplift.
(2) V-esotropia: also known as esotropia V sign, esotropia Vphenomenon, V-internal, convergent strabismus V syndrome , that is, the number of internal inclination increases when looking down, and the number of internal inclination becomes smaller or even disappears when viewed from the front, the internal inclination is closer than the far distance, and the lower oblique muscle function is too strong, and the patient may have a lower jaw. The performance of the adduction, the fixed vision of both eyes is small, and often has a horror.
(3) A-exotropia: also known as exotropia A sign, exotropia Aphenomenon, A-exotropia, dissociative strabismus A syndrome (divergent strabismus A syndrome) ), that is, when looking directly above, the number of external slopes becomes smaller or even disappears, while when viewed from directly below, the number of external slopes increases, and there is no change in the number of near-outside slopes in the distance, often the upper oblique muscles are too strong, and the adduction When the eye position is invaginated, the patient may have a mandibular adduction performance, and the eyes have a small solid vision and often have a horror.
(4) V-exotropia: also known as exotropia V sign, exotropia Vphenomenon, V-external oblique, strabismus V syndrome (divergent strabismus V syndrome) ), that is, when the angle is upward, the number of external slopes increases, while when viewed directly below, the number of external slopes decreases or even disappears. The external slope is much larger than the near view (the separation is too strong), and the lower oblique muscles are often too strong. The patient may have a mandible lifting phenomenon.
(5) X-phenomenon: X-phenomenon: that is, in the original eye position, the orthodontic or slight exotropia, when viewed directly above or below, the external inclination increases, showing an "X" shape.
(6) XA-phenomenon (X and A phenomenon): When the original eye position is slightly exotropy, the number of external oblique angles when looking upwards is increased less than when the direct oblique angle is observed.
(7) XV-phenomenon (X and V phenomenon): When the original eye position is slightly exotropy, the number of external oblique angles when looking upwards is much larger than the number of external obliques when looking directly downward.
(8) -phenomenon: -phenomenon: When the original eye position, the number of internal inclination is small or no internal oblique, and the number of internal inclination increases when looking upward and directly below.
(9) Y-phenomenon: Y-phenomenon: When the original eye position is observed and when it is gazing directly below, the number of external inclination is small or there is no external oblique, and when the eye is directly viewed, the number of external inclination is significantly increased, which is V- Variation of exotropia.
(10) , - Phenomenon ( , -phenomenon): that is, the number of external inclinations is small or no external oblique when the original eye position and the upper eye are gazing, and the external inclination is increased when gazing directly below, which is also the variation of V-external strabismus. Or the inverse of the Y-phenomenon.
2. Diagnostic criteria
The National Children's Amblyopia Prevention and Treatment Group (1987) of the Chinese Medical Association Ophthalmology Society stipulates that the diagnostic criteria for AV signs are:
(1) External oblique V sign: The slope when looking upward is larger than that when looking down (15, 8°~9°).
(2) Internal oblique V sign: The slope when looking upward is smaller than that when looking down (15, 8°~9°).
(3) Exotropia A sign: The slope when looking upwards is smaller than when looking down (10, 5°~6°).
(4) Internal oblique A sign: The inclination when looking upward is larger than that when looking down (10, 5°~6°).
Examine
AV syndrome check
No special laboratory tests are required.
1. General inspection
Check the naked eye (and correction) far and near vision, external eye condition, refractive status, refractive interstitial, gaze nature and fundus conditions.
2. Eye muscle examination
In addition to routine corneal examination, such as corneal mapping, occlusion, and diagnostic eye positions, the following examinations should be performed:
(1) Triangular prism and cover method to check the original eye position, the squint when gazing directly above and below.
(2) Retinal correspondence, fusion function, stereoscopic function check, and measurement of AC/A ratio.
(3) Double-eye solid vision examination to understand the scope of gaze and provide a basis for selecting surgical methods.
(4) The Hes screen checks the functional status of the extraocular muscles.
3. Precautions in AV syndrome examination
(1) If there is ametropia, corrective glasses should be worn during the examination.
(2) The patient should be allowed to look at the small visual target when looking close. In order to reduce the influence of the adjustment factor on the eye position, the 3D lens can be worn after the examination.
(3) The horizontal slope and the inclination of the upper and lower gaze positions were measured at 33 cm and 6 m, respectively. It was suggested that repeated examinations should be used as a basis for diagnosis.
(4) Mostly check the slope of the prism and cover method, and turn the angle of 25° up or down to check the inside and outside slope. Some people think that turning the angle of 15° is enough (Duke-Elder), because the gaze position is too up or too Downward is easy to cause illusion.
(5) Pay attention to check the oblique muscle function and squint:
1 The judgment of the superior oblique muscle function is divided into 4 levels according to the Parks classification method. The vertical inclination of the eyes is 30° and the left and right is 30°, and the vertical inclination of the eyes is changed. A.1 level: 10 °; B. 2: 10 ° ~ 19 °; C. 3: 20 ° ~ 30 °; D. 4: > 30 °.
2 The determination of the lower oblique muscle function is divided into three levels according to the Meng Xiangcheng classification method: A.1 level (1 degree): that is, the upper oblique appears when the internal rotation; B.2 (2 degrees): the extreme internal rotation Only the upper oblique is displayed; C.3 (3 degrees): the upper oblique appears when turning inward.
3 Rotation strabismus was determined by fundus camera photography. According to Kong Lingyuan's measurement method, the average value of the normal optic disc-central concave angle was 7.381°, the variation range was 1.429° to 13.333°, and the fovea was located at 0.343PD below the geometric center plane of the optic disc.
Diagnosis
Diagnosis and differentiation of AV syndrome
1. According to the patient's clinical manifestations and eyeball examination results, the diagnosis can be confirmed.
2. Diagnostic criteria
The difference between the gaze at the upward gaze and the downward gaze must be 10 to diagnose the A phenomenon; the difference between the two must be 15 to diagnose the V phenomenon, because the normal person is also mild when looking down. In order to further determine whether the AV phenomenon is a simple horizontal muscle factor or a vertical muscle factor, the squint measurement of each diagnostic eye position should be performed by the prism plus occlusion method or the same visual machine. The normal retina corresponding person should check with the same vision machine. It can be found that the AV phenomenon is accompanied by rotatory strabismus (which can also be confirmed by fundus photography), which is helpful for developing a surgical treatment plan.
