What is a cataract?
The lens is a part of the eye that helps to focus light on the retina. The lens lies behind the iris and the pupil. The lens is made mostly of water and protein. The protein is arranged in a precise way that keeps the lens clear as light passes through it. Much like an old camera in which the lens focuses light onto film where the image is recorded, the lens of the eye focuses light onto the retina where it is changed to nerve signals that are sent to the brain. In either situation, if the lens is not clear it does not allow light to pass through it properly and the result is a poor image. When the lens of the eye is clear, it is simply referred to as the lens, but when it becomes cloudy it is then diagnosed as a cataract.
HOW DOES A CATARACT DEVELOP?
As we age some of the protein may clump together and start to cloud the lens. Over time the cataract may progress and cloud more of the lens making it harder to see. There are several stages of cataract development and more than one type of cataract.
An early cataract is called an incipient cataract and at this stage it does not have much effect on vision and simply needs to be monitored for progression. This is one reason that we recommend yearly dilated eye exams. As a cataract progresses, it is graded from trace to 3+ or mature.
There are several different types of cataracts including:
Congenital – some babies are born with cataracts or develop them in childhood.
Traumatic – cataracts can develop after a traumatic injury to the eye, sometimes even years later. The severity of this cataract is related to the amount of trauma to the eye.
Nuclear Sclerotic – this is the most common type of cataract caused by the aging process. This aging causes a hardening and yellowing of the nucleus in the center of the lens. This type usually changes slowly and causes changes in a person’s eyeglass prescription.
Cortical – this type forms in the outer layers of the lens. This type of cataract can look like white spokes in a wheel pointing towards the middle of the lens.
Posterior and Anterior Subcapsular – this type develops under the capsule (bag) that surrounds the lens. Steroid medication use and high myopia are risk factors for this type of cataract.
It is possible for a patient to develop more than one type of cataract.