Which eye condition is characterized by a clouding of the lens?

Cataracts are specifically defined by a clouding of the lens of the eye, which can significantly impact vision. The lens is responsible for focusing light onto the retina, and when it becomes cloudy, it interferes with this process, leading to blurred vision and increased difficulty seeing, especially in low light or at night. This condition can develop gradually and is often associated with aging, but can also occur due to other factors such as diabetes, prolonged use of steroids, or other medical conditions.

In contrast, glaucoma is primarily related to an increase in intraocular pressure that can lead to damage of the optic nerve, often resulting in vision loss. Retinal detachment involves the separation of the retina from its underlying supportive tissue, which can lead to vision loss if not treated promptly. Myopia, or nearsightedness, is a refractive error where close objects are seen clearly, while distant objects appear blurred, and is not associated with any clouding of the lens. Therefore, cataracts are uniquely characterized by this specific clouding of the lens, making this the correct answer.