Most cataracts form slowly over time, so they are associated with aging. From the time of the eye’s lens formation, the lens continues to add layers of cells. These cells do not shed or slough off. Instead, as additional layers are created, the lens becomes more compact, increasing in size and density. At birth the lens is soft and malleable but as density increases with time the lens is no longer able to change shape. Most people notice beginning in their 40s that it becomes increasingly more difficult to change focus from distance vision to reading distance. The eye’s ability to change focus is known as accommodation. But as the lens increases in density, the eye gradually loses its ability to change focus. Presbyopia refers to the eye not being able to change focus. (Hence the need for bifocals, reading glasses or longer arms!)  One function of the lens is the absorption of UV radiation. There is oxidative stress on the lens related to the absorption of UV radiation. However, by performing this function, the lens acts to protect the light-sensitive retina, especially the macula. The macula allows us to be able to see faces, read, and see details so important for quality vision.  Over time, lens metabolism, altered lens protein structure, UV radiation, and cumulative oxidative stress induces changes in the lens that lead to age-related cataract formation. There are two common types of age-related cataracts which describe the location within the lens: nuclear and cortical. Nuclear cataracts are located in the center of the lens while cortical cataracts are located in the peripheral lens.  Nuclear cataracts give the center of the lens a yellow to brown color which can affect color perception especially dimming reds, blues and purples. As a nuclear cataract progresses, the center of the lens becomes more dense causing the lens to increase power. When this happens farsighted individuals will notice a temporary improvement in their distance vision. Cortical cataracts form like spokes on a bicycle wheel. These cataracts do not have as much visual disturbance early on. Later in their progression glare, halos around lights and decreased night vision become more problematic.