Strabismus is a common clinical disease in ophthalmology, with a prevalence of about 3%. There are many different types of strabismus, and there is no perfect clinical classification method. The classification of strabismus by different authors and monographs at home and abroad varies to varying degrees depending on the focus and factors considered, which often confuses beginners and ophthalmologists who are not specialized in strabismus and causes some trouble in clinical work.
In order to standardize and better guide clinical work, the Strabismus and Pediatric Ophthalmology Group of the Ophthalmology Branch of the Chinese Medical Association has organized experts in the specialty to discuss and revise the classification of strabismus suitable for clinical work in China. The classification method is based on the fusion status and divides strabismus into two categories: occult strabismus and dominant strabismus, and then further classifies strabismus in detail according to the direction of eye position skew, eye movement and changes in eye position skew angle in different gaze positions. The classification method is based on the opinions of mainstream and influential strabismus and ophthalmology monographs at home and abroad, and is not intended to favor one over the other. The new classification method is a trend that can reduce ambiguity and standardize clinical practice.
Hidden strabismus
Internal strabismus
(A) Congenital (infantile) internal strabismus
Most of the patients have similar visual acuity in both eyes and alternate gaze, and most of them are mildly hyperopic.
(B) Common internal strabismus
1. Adjustment strabismus
(1) Refractive accommodative strabismus [normal accommodative convergence/accommodation (AC/A) type]
The onset of the disease is usually at the age of 2~3 years; it may be intermittent in the early stage of the disease; the eye position is usually high to moderate hyperopia, and the eye position is corrected with glasses, which may be accompanied by amblyopia and normal AC/A value.
(2) Non-refractive adjustment internal strabismus (high AC/A type)
The onset of the disease is usually at the age of 1-4 years; most of the eyes are mildly hyperopic; the near strabismus is significantly greater than the far strabismus.
The degree of near strabismus is significantly greater than that of far strabismus, and the AC/A value is high.
(3) Partially adjusted internal strabismus
The strabismus is reduced after wearing glasses, but the eye position cannot be completely corrected.
2. Non-adjusted internal strabismus
(1) Basic type: The strabismus is similar in magnitude between near and far.
(2) Over-agglomeration type: Near strabismus is greater than far strabismus, but the AC/A value is normal.
(3) Insufficient separation type: the distance strabismus is greater than the near strabismus.
3.Minor internal strabismus
4. Periodic strabismus
5. Acute common strabismus
(3) Secondary internal strabismus
After external strabismus surgery
2. Perceptual internal strabismus
(iv) Non-common strabismus
1. Paralytic internal strabismus: spreading nerve paralysis
2. restrictive internal strabismus: high myopic restrictive internal strabismus, and
(2) Restrictive strabismus: high myopic restrictive strabismus, Duane’s retrobulbar syndrome, Moebius syndrome, thyroid-related ophthalmopathy, orbital burst fracture, etc.
(v) Internal strabismus with nystagmus
External strabismus
(I) Congenital exotropia
The onset is within 1 year of age; the strabismus is large and constant.
(B) Common exotropia
(1) Intermittent exotropia: Onset at an early age, alternating between exotropia and exotropia; dominant exotropia can be induced by mental inattention or covering one eye.
(1) Basic type: The strabismus of distance and near vision are similar in magnitude.
(2) Overdistribution: The strabismus is greater in the distance than in the near (≥ 15△). After covering one eye for 30~60 min, the distance strabismus is still greater than the near strabismus.
(3) Insufficient integration: near strabismus is greater than near strabismus (≥ 15△).
(4) Similarly, the separation is too strong: similar to the basic type, but after covering one eye for 30~60 min, the near strabismus increases and is similar to or greater than the far strabismus.
2. Constant exotropia
(C) Secondary exotropia
1. Spontaneous transformation of internal strabismus into exotropia after corrective surgery and internal strabismus
2. Perceptual exotropia
(iv) Non-common exotropia
1. Paralytic exotropia: paralysis of the motoneural nerve
2. Restrictive exotropia: Duane’s retrobulbar syndrome, congenital extraocular muscle fibrosis, etc.
AV strabismus
AV type strabismus refers to the existence of vertical non-conformity in horizontal strabismus, and there is a significant change in the degree of horizontal strabismus when gazing upward and downward, mainly due to the abnormal function of the oblique muscle. The following types of strabismus can be distinguished according to the 25° upward and 25° downward rotation of the eyes and the original position of the strabismus.
1. V-type exotropia: the upward strabismus is greater than the downward strabismus (≥15△).
2, V-type internal strabismus: downward gaze strabismus is greater than upward gaze (≥15△).
3, A-type exotropia: downward strabismus is greater than upward strabismus (≥10△).
4, A-type internal strabismus: upward gaze strabismus is greater than downward gaze (≥10△).
V. Vertical rotational strabismus
Vertical strabismus is mostly a non-common strabismus.
(a) Upper oblique muscle paralysis
1. congenital superior oblique muscle palsy
2. Acquired superior oblique muscle palsy
(ii) External rotational strabismus: mainly seen in acquired bilateral talocrural nerve palsy
(iii) hyperfunction of the inferior oblique muscle
(iv) hyperfunction of the superior oblique muscle
(v) Lower oblique muscle palsy: rare in clinical practice, mostly unilocular.
(vi) Insufficient upward rotation of one eye (bilateral upward rotation muscle paralysis)
(vii) Restrictive vertical strabismus: thyroid-related eye disease, orbital burst fracture, etc.
VI. Special types of strabismus
1.Dissociated strabismus [DVD, dissociated horizontal deviation (DHD), dissociated torsional deviation (DTD)]
2.Intermittent exotropia combined with moderate internal strabismus
3, congenital extraocular muscle fibrosis
4.Duane’s retro-ocular syndrome
5.Moebius syndrome
6.Brown syndrome
7.Chronic progressive extraocular muscle paralysis
8.Severe myasthenia gravis
9.Orbital burst fracture
VII. Central paralytic strabismus
Central paralytic strabismus is divided into nuclear, inter-nuclear and supranuclear.