In training for myopia, the training is conducted with the object being placed at a location farther than the user's own vision D. In training for hyperopia, the training is conducted, with the object being placed at a near distance D (e.g., the external visual range of 40 cm is 1.5D in Boramaenun, and 30 cm 2.25D). In training for astigmatism, training is carried out to put right the center of a distorted focus by the use of astigmatism grid cap. With the astigmatism grid cap, the user conducts training for removing astigmatism by recognizing a dim line among several lines until it looks like a solid line - trying to see clearly a line at a dim region in the 360-degree direction from the center of a circle.