Biological eyes last for only a limited amount of time. Most people lose the ability to focus their eyes by the time they are 50, requiring bifocal lenses to see either near or far, and at some point their retina clouds over, a condition known medically as a cataract, further robbing the person of their ability to see.
Now, Discovery News is reporting that medical researchers at the Massachusetts Institute of Technology have produced artificial retinas for restoring sight in people who are blind due to retinal problems.
Artifical retinas actually already exist, being focusable bags of saline water that restore the existing ability of the eye to see, solving the problem for people with cataracts but not presbyopia. This system is different: It turns the eye into a low-resolution camera that feeds directly to the brain. The camera is good for the user's entire remaining life. It contains a battery that can be recharged inductively, so the user can recharge it with a small electric pad on their face, perhaps while sleeping.
This is encouraging, and I think within my lifetime, someone will invent artificial eyes that can see better than biological ones, and it will become worth it to have ones eyes outright replaced.