What type of lens power is measured to correct spherical vision issues?

Sphere power is the term used to describe the lens power specifically designed to correct spherical vision issues, which refer to conditions like myopia (nearsightedness) and hyperopia (farsightedness). Spherical lenses have a uniform curvature that helps to focus light directly onto the retina, thereby improving vision for individuals who experience these common refractive errors.

In contrast, prism power addresses issues related to misalignment of the eyes and aids in correcting binocular vision problems but does not directly correct spherical refractive errors. Cylinder power is relevant for astigmatism, where light is not focused evenly due to irregularities in the cornea or lens. Vertex power is related to the thickness and curvature of the lens but does not pertain to the spherical correction itself. Therefore, sphere power is the correct focus for addressing spherical vision issues.