Popular Science | Understanding Strabismus

1. Strabismus

Strabismus refers to the inability of the two eyes to look at a target at the same time. When one eye is fixed on a target, the other eye deviates from it. The causes of strabismus are relatively complex, with both congenital and acquired factors.

Types of strabismus

There are many types of strabismus, which can be divided into the following categories:

Heterotropia, esotropia, exotropia, AV strabismus, vertical rotational strabismus, special types of strabismus, etc.

3. Harm of strabismus to vision

It mainly causes binocular vision abnormalities and amblyopia.

Normal binocular vision has a perfect coordination relationship between the two eyes. The image of external objects formed by the normal corresponding points of the retinas of the two eyes can be perceived as a complete single image after being transmitted to the brain.

Because strabismus patients have deviated eye positions, the coordination between the two eyes is disrupted, which can cause diplopia and confusion, and further cause binocular vision abnormalities such as visual inhibition, abnormal retinal correspondence, fusion and stereoscopic vision abnormalities.

4. How can parents initially detect whether their children have strabismus?

1. Flashlight method

The examiner holds a flashlight and directs a light 33 cm in front of the examinee, instructing the child to look at the light source.

If the corneal light reflection point is located in the center of the pupil, the eye is in the right position;

If the corneal light reflection point appears on the inside of the pupil, it is exotropia; if the corneal light reflection point is on the outside of the cornea, it is esotropia. See the figure below

2. Monocular cover test

The monocular cover test can be used to check whether there is latent strabismus and determine the direction of strabismus.

(1) The child sits upright and faces the parent.

(2) The parent holds a sight mark (or other target object) and places it 33 cm in front of the child. The parent tells the child to look at the sight mark. The parent quickly covers one eye with one hand and observes the movement of the other eye.

(3) Then repeat the cover test on the other eye.

If neither eye moves during the cover test, the child's eyes are in normal alignment and there is no manifest strabismus.

If the child has manifest strabismus, parents can observe the movement of the eye position by briefly covering the fixation eye and forcing the deviated eye to move to the normal position to fixate on the sight mark. For example, moving from the nasal side to the normal position is esotropia, moving from the temporal side to the normal position is exotropia, and moving from the upper side to the normal position is hypertropia.

Kind tips

The flashlight method and the cover examination method are simple and easy to perform. If you suspect your child has strabismus, parents can also try the above two methods at home to make a preliminary diagnosis. However, the examination requires the child's high cooperation and often needs to be repeated many times. The examination results may not be accurate. Parents should not make conclusions on their own. If you have any questions, go to the hospital for a clear diagnosis as soon as possible.

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