For example, myopia is corrected with a scattering (in particular, a biconcave) lens, farsightedness – with a collecting (in particular, a biconvex) lens. Therefore, if it is possible, without touching the glasses, to determine whether they are convex or concave, then it is possible to establish the type of visual defect. You can also substitute glass lenses under the light source. If an image is formed on the surface that serves as a screen, then the lens is collecting, if there is no image, then it is scattering.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.