Final answer:
More than 43 million people with presbyopia have 1.0 D or greater of astigmatism, a vision defect that can be partially corrected with eyeglasses.
Step-by-step explanation:
In the case of the presbyopic population, more than 43 million have 1.0 D of astigmatism or greater.
Astigmatism is a vision defect characterized by an unevenness or asymmetry in the focus of the eye. It occurs due to irregularities in the shape of the cornea, lens, or retina. Astigmatism can be partially corrected with eyeglasses having a cylindrical correction.
Therefore, more than 43 million people with presbyopia have 1.0 D or greater of astigmatism, and they may require eyeglasses with a cylindrical correction to help improve their vision.