Which of the following describes cataracts?

The correct choice highlights that cataracts are characterized by a cloudy appearance of the lens in the eye. This cloudiness occurs when proteins in the lens of the eye begin to clump together, causing the lens to become opaque. This condition significantly affects the way light passes through the lens, leading to vision impairment.

While transparency of the eye is crucial for normal vision, it does not describe cataracts, as cataracts involve a loss of that transparency. Similarly, while a reduction in sight and complete blindness can result from cataracts, they do not specifically define what cataracts are. The defining feature of this condition is indeed the cloudiness of the lens itself.