Presbyopia is a visual condition that makes reading or working on something near to the eyes difficult. This condition is due to the eye's natural ageing process, which usually manifests over the age of 50, or at 40 at the earliest, developing to maximum presbyopia by 60. Between these two time frames, presbyopia rapidly progresses, hence the need to get new glasses fitted so frequently. The eye's crystalline lens stiffens with age, thus preventing correct focus, in other words the crystalline lens' capacity to bend its curvature in order to direct the light rays to converge on the macula, the optical center of the eye's retina. Treatment requires patients to wear glasses. It is worth noting that myopic individuals become presbyopic earlier, while sufferers of hypermetropia progress to this condition later.