Age-related cataracts develop in two ways: First, clumps of protein reduce the sharpness of the image reaching the retina. Because the lens is mainly made up of water and protein, when the protein begins to clump together, it can cloud the lens and reduce light from reaching the retina. The clouding may become severe enough to cause blurred vision. Most age-related cataracts develop this way. When a cataract is small, the cloudiness affects only a small part of the lens, so you may not notice any changes in your vision. Cataracts tend to "grow" slowly, so vision can worsen gradually. Over time, the cloudy area in the lens may increase, and the cataract may grow, thus making seeing more difficult. Vision will become more dull or blurrier.
The second way in which a cataract can develop is when the lens begins to change colours, taking on a yellow or brownish hue. As the clear lens colours with age, vision may appear to be browner. At first, the tinted vision may not be noticeable. But over time, increased tinting may make it more difficult to see clearly. The gradual change in colouration does not affect the sharpness of the image transmitted to the retina. Those with advanced lens discolouration may not be able to see blues or purples.