Before age 40 our lens is clear and flexible allowing us to focus on things at near. Even if you have had “good eyes” and “normal vision” all your life, your vision is likely to begin to change in a number of ways as we progress from our 40’s, to our 50’s and then our 60’s and beyond. The most obvious changes to our vision occur as a result of changes in the natural lens of the eye.
As we reach our mid-forties, everyone begins to experience the problem of our "arms becoming too short", and near vision begins to fade. This condition is called presbyopia and gets progressively worse as we age. Eventually, we start wearing bifocals or reading glasses, or if you are nearsighted, you begin to take our glasses off to read.
A second problem starts as we reach our fifties, about that time our lens starts to become slightly cloudy. Eventually this cloudiness progresses to the point where we don't see as well even with glasses. At this point, we call the cloudiness a cataract, and if we all live long enough, we will all develop cataracts. Cataracts are a natural part of the aging process.