b. Hyperopia. This out-of-focus condition results when the eye is
unable to extend to the required focal length for a clear picture (Figure 3)
and is commonly referred to as farsightedness.
c. Astigmatism. Basically, astigmatism is the inability to
simultaneously focus different meridians. If, for example, the individual
focuses on power poles (vertical reference), the wires (horizontal
reference) will be out of focus (Figure 4).