The numericals involving the human eye will be solved by first finding out the kind of eye defect. Measure the object distance (u) and image distance (v), and the smallest distance of clear vision was 25 cm, which is the least distance of distinct vision in a normal eye. Use the lens formula (1/f=1/v -1/u) to obtain the focal length (f). Subsequently, P = 1/f (f in meters) to derive the lens power. Lastly, test the sign of P: A positive value means that the lens used is convex to correct hypermetropia, whereas a negative value means that the lens used is concave to correct myopia.