A prism is an optical element composed of two non-parallel planes. It is called a triangular prism because its main cross-section is triangular. It is mainly used for orthotopic training of the eye muscles and correction of heterotropia. The prism is a very important method to correct children's strabismus and eliminate diplopia. Recommended reading: Four measures to keep children away from strabismus

When correcting with a prism, you can also use the lens to shift the center or add a prism to the lens. In order to obtain the required prism power, its bottom direction is opposite to the direction of the oblique strabismus axis deflection. For example, the upper oblique strabismus is corrected with a bottom-down prism. Then, what are the mirroring principles of the prism?

1. The principle of ordinary prism to mirror:

1. Using the method of equal division, the prism required for correction is divided equally between the two eyes and each eye does not exceed 6△. If the right eye needs 3△ bottom-up correction, the prism is divided equally into both eyes: 1.5△degree for the right eye Bottom up, left eye 1.5△ bottom down.

2. Non-equalization method: Considering the patient's comfort level after being equipped with glasses, the two-eyes non-equalization method can be used for glasses. A small amount of glasses should be given to the dominant eye and more power should be given to the non-dominant eye.

3. When fitting glasses, consider that the deflection is a mixed cause. When the vertical deflection is corrected, the normal reflection and fusion ability is often improved due to the horizontal strabismus. Therefore, it can be considered that the correction of the vertical cryptic part by the prism will greatly help the relief of all the interference symptoms of horizontal strabismus.

On the contrary, the horizontal error and the vertical deflection exist. If only the horizontal strabismus is corrected, the correction result will almost fail. When the skew is very small, lens shift can be used as a cheap stopgap method, and sometimes the same correction result can be obtained.

Second, the principle of film-like prism giving mirror

1. If the squint is more than 6△, the thickness of the prism will increase, causing difficulty in wearing.

2. Combining the higher degree of hyperopia and nearsightedness at the same time, it is necessary to add a prism to correct the hyperopia and nearsighted glasses at the same time.

3. Strabismus with a single eye exceeding 15△ needs to be corrected.

Wearing a prism can eliminate diplopia, correct eye position, and relieve visual fatigue. It has a great effect on our eye health. If you have a strabismus, go and correct it.