How can the visual deficiencies recognized as myopia

Question

How can the visual deficiencies recognized as myopia and hypermetropia be optically explained?

Answer 1

Myopia is visual situation in which images are formed before (in front of) the retina. Hypermetropia is visual condition in which point of image formation is beyond (behind) retina. Actually myopia is due to a raise in distance between retina and crystalline lens, mainly caused by the slight flattening of eyeball. In hypermetropia the retina is too close to the crystalline lens because of slight shortening of eyeball.

In myopia near point and far point of the vision come closer (the refractivity of crystalline lens which corresponds to maximum distension capacity of ciliary muscles is not enough to offer visual accommodation). In hypermetropia the ciliary muscles are not capable to contract more to compensate the inadequate position of retina, that is, the near point becomes more distant.