The refractive error of 0.4 vision may be of various types, including high degree of hyperopia or astigmatism, or myopia. If a patient is farsighted, a vision of 0.4 may require 400-500 degrees of farsighted glasses. If you are a patient with astigmatism, you may need about 300-400 degrees of astigmatism glasses to improve your vision. If you are a nearsighted patient, you will usually need about 200 degrees of nearsighted glasses to improve your vision to 0.4. Therefore, the exact type of glasses and the number of degrees of glasses to be prescribed will depend on the results of the optometry. It is possible that the patient may be farsighted or nearsighted and may have a combination of astigmatism, so it is important to have the glasses tested before prescription.