ABSTRACT
The crystalline lens was not locked in during the onset of myopia. It can still flatten to a certain extent to bring some distant objects into focus. The tension of the oblique muscles does not cause the ciliary muscle to spasm. Instead, it places a restriction on how much the ciliary muscle can relax—and thus how much the lens can flatten out.
The rays of light from near objects are divergent. Wearing a minus lens diverges the light rays even more. The crystalline lens increases its bulged shape to converge the rays onto the retina. The oblique muscles would tighten up some more to alleviate the stress placed on the ciliary muscle. In most cases of moderate myopia, the alleviation is only partial. The result is a partial resistance to ortho C. In severe cases of myopia where the power of the minus lenses is higher, there would be a total resistance. It is the eventual spasm of the ciliary muscle in the attempt to compensate for the longer focal length in the near and midrange that causes a loss of depth perception.
An ortho C lens only attends to the indirect induction of stress—not to any direct induction. Relaxing the oblique muscles by ortho C only deals with the tension of the ciliary muscle that was indirectly induced. If spasticity sets in due to a direct induction of stress, you also have to deal with it separately.
