If the lenses of a patient wearing -15.00 spheres are moved closer to their eyes, what will happen to the effective power?

When the lenses of a patient with a -15.00 sphere are moved closer to their eyes, the effective power of the lenses increases, leading to an increased minus power effect. This phenomenon occurs because as the distance from the eye to the lens decreases, the light rays are refracted more strongly.

In the case of negative lenses (which have a minus sign), bringing the lens closer causes the virtual image created by the lens to move further away, which effectively increases the strength or power of the lens from the perspective of the wearer. Therefore, the patient experiences a greater degree of correction for their nearsightedness, effectively amplifying the negative power of the lens.

This principle can also be seen in the behavior of magnifying glasses and how they function at different distances. The effects of modifying the distance between the lens and the eye are vital in understanding visual acuity corrections, especially in strong prescriptions like -15.00 spheres, where small changes can lead to significant differences in visual performance.