The adjustment force used by people when they look close will bring a corresponding amount of collective force. Under normal circumstances, our normal eyes, every time we use the adjustment force of 1D, will bring a set of 4△, so that people's eyes can keep lasting comfort when they look close.
If the adjustment function is changed, but the set remains unchanged, the eye will exert too much force with the medial rectus muscle and produce set. In the long run, there will be excessive concentration.
When convergence is excessive, the lateral rectus muscle is stretched, which overtresses the temporal side wall of the eyeball, thus making the eyeball flatter, so that the axial length of the eyeball will also become longer and the degree of myopia will deepen.
The principle of progressive film is to prevent myopia from deepening by relaxing eye accommodation. Using progressive film to control myopia in adolescents is more suitable for people with high AC/A ratio. Because of the high AC/A ratio, adjustment leads to too much collection. Relaxation and adjustment can reduce the amount of collection and make the eyes more comfortable.
Extended data:
Myopia of exotropia is often caused by insufficient convergence. When wearing progressive lenses, the near diopter decreases, and the adjustment is less, which leads to insufficient stimulation to convergence, which will promote the increase of exotropia and the adjustment function of myopia itself is insufficient.
If the near-use luminosity decreases, normal adjustment is not needed when near-use. Over time, the eye's adjustment function is lower, which is easier to promote the development of myopia.
Baidu Encyclopedia-Progressive Lens