A cataract is a clouding or discoloration of the normally clear lens of the eye. This clouding, in most cases is a normal aging process and usually matures in the later years of life. It can be compared to a window that is frosted, steamed or yellowed, which results in reduced or impaired vision. There are a lot of misconceptions about cataracts, and this information will aid in clarifying some of the important facts about this common condition.
The lens, or crystallin lens of the eye is a biconvex, transparent structure positioned just posterior to the colored part of the eye (the iris). Along with the front surface of the eye (the cornea), the lens helps to refract light to be focused on the retina which allows you to see clearly. The lens contributes to about 1/3 of the eye's focusing power, the cornea contributes the other 2/3. The lens also acts as an "autofocus" mechanism so you can see clearly at various distances, especially up close. This adjustment of the lens is called accommodation.
Many different factors can be the cause of a cataract formation. A cataract is NOT a film that has grown over the front of the eye, but a clouding of the crystaline lens inside the eye. Aside from aging, cataracts can develop due to certain diseases, medications, eye injuries, or long-term exposure to sunlight. Your genes may also play a role. As light enters an eye with a cataract, the rays are scattered and cannot pass through the lens easily. As a result your vision is blurred.
A cataract starts out small and at first has little effect on your vision. You may notice that your vision is blurred a little, like looking through a cloudy piece of glass or viewing an impressionist painting. A cataract may make light from the sun or a lamp seem too bright or glaring. Or you may notice when you drive at night that the oncoming headlights cause more glare than before. Colors may not appear as bright as they once did.
The lens is composed of several layers, and the various types of cataracts are determined by which layer is affected. The type of cataract you have will affect exactly which symptoms you experience and how soon they will occur. Although there are many different types of cataracts, only the most common types will be discussed here:
- Nuclear: this cataract forms in the nucleus, the center of the lens, and is due to the natural aging process (UV exposure). It typically blurs distance vision more than near, and cause a myopic shift (increase nearsightedness).
- Posterior Subcapsular (PSC): this is a plaquelike opacity near the posterior aspect of the lens. Glare and difficulty reading are common complaints. It is usually associated with ocular inflammation, steroid use, diabetes, trauma, or radiation. It classically occurs in patients <50 years old.
- Cortical: this cataract forms in the lens cortex and gradually extends its spokes from the outside of the lens to the center. It can cause glare, but often go unnoticed until central changes develop. Many diabetic patients develop cortical cataracts.
- Mature: this cataract is defined as lenticular changes sufficiently dense to totally obscure your vision. Often, light perception is the only thing a patient can see.
Cataracts at first are easily managed by the use of an updated glasses prescription, appropriate lighting, and other visual aids. Consider surgery to remove the cataract when it impairs your vision, and starts to reduce your quality of life. You don't have to live with this kind of reduced vision. Cataract surgery is in fact the most common surgery performed in the United States with over 3 million people per year having it done. During the surgery, the surgeon will remove the clouded lens and in most cases replace it with a clear, plastic intraocular lens (IOL). New IOL's are being developed all the time to assist in reaching the best results for the surgeon and patient. Ask us about all the options that are available to you.