A cataract is a situation where the eye lens becomes cloudy or has impurities within it. This blocks the light rays from traveling through the lens to the retina and causes blank patches (also called blind spots) to appear in the picture. The effect is similar to looking at a jigsaw puzzle which has missing pieces or looking at a piece of white paper with one spot of black ink on it. More severe cases of cataract will cause increasingly bigger blank patches. With a cloudy lens, a person may not experience entire loss of view in affected areas but rather a dimmed portion.
There are three groups of reasons for a cataract to form and four basic varieties of developments. The groups of reasons are senile, congenital, and secondary. The varieties are pinpoint, spot, patch, and complete.
The lens of the eye is constantly growing through our lifetime. When lens material develops, it takes its place over (not replacing) the old material. This action naturally causes the compression of the total lens mass as well as a slight thickening of the size of the lens. As we get older, the lens becomes more dense, less flexible, and less transparent (clear). The natural loss of flexibility creates the condition called presbyopia. The loss of transparency is what causes senile cataract.
Many cases of cataract occur in persons over 40 years of age, but they can be present at any time of life. Congenital cataract is present from birth and is caused by problems during fetal development. Secondary cataract is either caused by nutritional problems (mostly in poverty stricken countries), eye injury, diseases, or due to side effects of medications. Basically if it is not present at birth or caused by the natural aging process, it is called a secondary cataract.
Pinpoint cataract is very tiny spots of impurity on the lens which often do not result in lost view and sometimes go unnoticed until revealed during a vision exam. Spot cataract is bigger impure areas on the lens which may be noticeable in the view but usually don't show unless looking at a solidly colored background such as a wall or paper. These can also create an illusion of lights having a halo around them or appearing as a ring with an dark center. Both patch cataract and complete cataract are more developed then pinpoint or spot types and do make themselves very obvious in your view, with complete cataract affecting the whole picture.
Presence of a cataract doesn't always affect a persons view. Some cataract develop quickly while others grow over a long period of time. Those that gradually grow give you a period of adjustment (natural function of our eyes) so that you are less likely to notice them as they mature (medical terminology calls it getting ripe). Length of maturity and impact on vision vary between the type of cataract and the person.
Note that the term cataract is usually spoken in plural as cataracts. Many people suffer from multiple cataract which is why the term is accepted in both singular and plural form. While it is possible to have a cataract condition in both eyes, normally only one is affected. Even if both eyes have a cataract, each one will likely be of different size, location, and maturity. Cataract do not spread from one eye to the other, but similar circumstances (chemistry, genetics, etc) may make somebody more likely to develop cataract in both eyes.
With regular vision exams, a cataract will most likely be detected before it actually affects the vision. Cataract may take many years to reach maturity and there is no guarantee they even will mature. The degree of severity and the rate of maturity are things which should be discussed with a doctor because it differs for every person.
A cataract is dealt with by removal of the impurity on the lens. Incision (where a surgeon physically cuts open) surgery of the lens used to be the only option for cataract removal. With laser surgery now being a form of treatment, incision surgery is a less common way of dealing with cataract though it is still an option on some cases. With either form of surgery, the portion of the lens which was affected by the cataract is now missing. Light rays will be able to travel through this part of the lens, but because the lens is still damaged there, absolute focus at that point is impossible. This is why a person who has had a cataract removed may need to wear glasses or contact lenses after their surgery when they may not have needed them prior. The severity of the removed cataract will determine the type of corrective glasses or if needed at all.
Incision surgery is where a doctor physically cuts open the eye and cuts out the affected portion of the lens. As with most any surgery, there is a chance of infection and a period of banned or restricted use after surgery. Laser surgery uses a laser to break up and/or burn off the impurity. The chance of infection is greatly reduced since the eye has not been physically cut into (Note: there is a cut made in the cornea). Laser surgery is often performed on an out patient basis now where the person is allowed full use of their eye even on the following day. By the way, ANY surgery involves a risk. Laser surgery of the eye is considered to be a low risk treatment, but don't let any doctor tell you there is NO risk.
Treatment for a cataract has come a long way in the last decade, as well as the ability to detect them even earlier. However, unlike other diseases, a doctor may not recommend corrective surgery for a cataract as soon as it is detected. There are as many different views on when to do the surgery as there are doctors to perform the actual event, but most patients don't understand why surgery would be put off. You would think that it would always be best to remove a cataract when it is first detected, but many professionals feel that dealing with cataract before it is mature raises the risk of its return (continued growth beyond the point of removal). This may be due to some patients having renewed cataract from an incision surgery which didn't remove everything, but many doctors still wish to wait until the cataract matures even before laser surgery.
Another reason to delay surgery is in judging the overall benefit to the patient's vision. If a person's vision is not yet affected by a cataract, why risk surgery to fix it since the person will not see any difference. A cataract in the center of the lens (in the middle of the view) is more worthwhile to remove then one at the edge. Also, other problems with the eye might increase the risk of cataract removal or make the cataract a lower priority. These are issues which should be discussed with a doctor.
Many people with untreated cataract conditions tend to adjust to the view and learn to not pay attention to the spot if there is even one visible. Others are so bothered by the condition that they pressure doctors into removal before a doctor feels it is time to do so. Many insurance companies side with the doctors judgment of severity over the patients opinion, but also use their own discretion in looking over pre-surgery documentation to determine if they will pay for it. A cataract is called an annoyance disease when its presence only affects a small portion of the view. Most medical professionals agree that the presence of a cataract does not shorten the life of the (remainder of the) lens or cause further damage to the eyes.
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