Cataracts

A cataract is a clouding of the lens in the eye that affects a patient’s vision. Most cataracts are related to aging, meaning that cataracts are very common in older people. By age 80, more than half of all Americans either have a cataract or have had cataract surgery to fix the issue. A cataract can occur in either or both eyes at the same time, but it cannot spread from one eye to the other.

The lens is a clear part of the eye that helps to focus light, or an image, onto the retina. The retina is the light-sensitive tissue at the back of the eye. The retina contains rods and cones. Rods are the most numerous photoreceptors in the retina. It is estimated that there is around 120 million in each eye. Rods are more sensitive than cones, but they are not sensitive to color. In other words, rods sense black and white and aid when you are in darkness. The rods are also much better at sensing movement and motion because they dominate your peripheral vision.

Cones are less numerous within your eye, but they are still very important. Cones are your color sensors. It is estimated that there are 6 to 7 million cones within the retina. The cones can be divided into red cones, green cones, and blue cones. Red cones account for 64%, green accounts for 32%, and blue is 2%. Cones are not as sensitive as rods, but they are quicker to react to changing light levels, which is why your cones are more active during the daytime. Your cones are also responsible for all high resolution vision. Your eye ensures that the light is always focused on the fovea centralis by moving because most of the cones in your retina are found within the fovea centralis.

In a normal eye, light passes through the lens, which is transparent, then onto the retina. Once it reaches the retina, light is changed into nerve signals that are sent to the brain. The lens must be clear for the retina to receive a sharp image. If the lens is cloudy from a cataract, the image you see will be blurred.

The lens lies behind the iris and the pupil. It works in a way very similar to a camera lens. It focuses light onto the retina at the back of the eye, where an image is recorded. The lens also adjusts the eye’s focus, letting us see things clearly both up close and far away. The lens is made of mostly water and protein. The protein is arranged in a very precise way that keeps the lens clear and lets light pass through it. But as we age, some of the protein begins to clump together and start to cloud a small area of the lens. This cloudy area is a cataract. Over time, the cataract may grow larger and cloud more of the lens, making it harder to see out of the affected eye. Researchers suspect that there are several causes of cataract. Some of the common causes are smoking and diabetes. Or, it may just be that the protein in the lens just changes due to the wear and tear it takes over the years.

Age-related cataracts can affect your vision in two ways: clumps of protein reduce the sharpness of the image reaching the retina, or the clear lens slowly changes to a yellowish/brownish color, adding a brownish tint to vision.

When the protein that makes up the lens clumps up, it clouds the lens and reduces the light that reaches the retina. The clouding may even become severe enough to cause blurred vision. Most age-related cataracts develop from protein clumps. When a cataract is small, the cloudiness affects only a small part of the lens. You may not even notice any changes in your vision. Cataracts tend to “grow” slowly, so vision will get worse gradually. Over time, the cloudy area in the lens may get larger, and the cataract may increase in size. Seeing may become more difficult. Your vision may get duller or blurrier.

As the clear lens slowly colors with age, your vision gradually may acquire a brownish shade. At first, the amount of tinting may be small and may not cause a vision problem. Over time, increased tinting may make it more difficult to read and perform other activities in your daily routine. However, this gradual change in the amount of tinting does not affect the sharpness of the image transmitted to the retina.