What type of lens is used primarily to correct myopia?

Myopia, commonly known as nearsightedness, occurs when the eye's shape causes light rays to focus in front of the retina rather than directly on it. This results in distant objects appearing blurry while close objects can be seen clearly.

To correct this condition, a concave lens is used. Concave lenses are thinner at the center and thicker at the edges, which helps diverge light rays before they enter the eye. This divergence of light allows the rays to focus further back, directly on the retina, thereby improving the clarity of distant vision for someone with myopia.

In contrast, convex lenses, which are thicker in the center, are used to correct hyperopia (farsightedness) as they converge light rays to bring the focus closer to the eye. Aspheric lenses are designed to enhance optical performance and reduce aberrations, but they are not specifically aimed at correcting myopia. Cylindrical lenses are used for astigmatism, a condition where the light is not focused evenly on the retina due to an irregularity in the cornea or lens shape.

Thus, the use of a concave lens specifically addresses the focal point issue associated with myopia, making it the appropriate choice for correction in this case.