In which of the following defects, the lens of the eye becomes cloudy and opaque?

• A cataract is an acquired defect of the eye in which the eye lens becomes opaque or cloudy. 
• It is usually caused in old age and in severe cases, it can lead to loss of vision. 
• It can be treated with a procedure where the natural lens of the eye is replaced with a new artificial lens. 

Hence Cataract is the correct answer.