Which of the following best describes a cataract?

A cataract is best described as an abnormality in the morphology or biochemistry of the lens of the eye, which leads to its clouding. This clouding interferes with light passing through to the retina, resulting in reduced visual clarity. As the lens becomes less transparent, it alters the way light is refracted, causing various degrees of vision impairment.

The other options do not accurately represent the characteristics of cataracts. Increased light transmission is contrary to what occurs in the presence of a cataract, as clouding decreases light's ability to pass through the lens. Normal optical function is also not applicable, since cataracts disrupt the normal focusing ability of the lens. Enhanced visual acuity certainly does not describe a cataract, as the condition is known to diminish visual sharpness rather than improve it.