I will continue our discussion on cataracts in recognizing March as National Cataract Awareness Month.
A cataract is a clouding of the lens of the eye. This clouding can be a result of medical conditions, aging, social and environmental causes, injury and medications. As the clouding becomes more intense, the vision changes and becomes less clear. While there are no known causes of cataract development, there are a number of risk factors.
There are three main types of cataracts. One, two or all three may be present in any given person. These three types of cataract, the nuclear, cortical and sub-capsular type, make up more than 98% of all cataracts. Each type of cataract affects a different part of the lens, causing different symptoms and vision problems.
A nuclear cataract is by far the most common. In this form of cataract the nucleus, or center of the lens begins to harden and change color. As the color changes from clear to yellow to dark amber it also progressively hardens. If it is allowed to progress further it will ultimately turn pure white and can be seen as a white pupil in the eye. This progression occurs very slowly, typically over many years and affects the distance vision the most. It is not unusual for a person with a purely nuclear cataract to not notice these slow changes because the brain adapts to this slowly progressive decrease in vision. Usually, a person with a pure nuclear cataract will complain that they were unable to pass their vision test to renew their driver’s license as the first sign that the cataract has progressed. I once surprised a patient by telling him that he had a cataract. He responded by assuring me he did not have a cataract but instead drove a Lincoln (he was also a little hard of hearing).
The next most common form of cataract is the cortical cataract. It usually begins as spoke-like opacities starting at the edge of the lens and ending at the center of the lens. These spokes then widen over time into pie-wedge shaped opacities that interfere with light passing through the lens. This causes glare, light sensitivity and a decrease in color contrast. Most people complain of halos around car lights, traffic lights and streetlights. They commonly find that it becomes too difficult to drive at night or on dark rainy days. This type of cataract can interfere with both distance and reading vision more quickly than the nuclear cataract. Many people with diabetes, high cholesterol and other medical conditions will develop these types of cataracts.
The third most common cause of cataracts is the sub-capsular cataract. This forms at the back of the lens on the elastic membrane or capsule of the lens. It typically begins as a small opacity that looks much like a clear scab. It then spreads across the surface of the capsule blocking and distorting the light entering the eye. This type of cataract tends to progress much faster than the other two forms causing severe glare, light sensitivity and blur. It can go from a small insignificant opacity to a sight-blocking cataract in 6 months or less. The sub-capsular cataract is most commonly seen in younger patients, diabetics, eye trauma victims and with certain medications, especially cortisone.
The signs and symptoms of cataract should not be ignored. Blurry vision, especially when outdoors, difficulty finding the edge of stairs or curbs, halos or streaks of light around headlights or streetlights, poor vision on cloudy and rainy days, difficulty reading road signs on bright sunny days, vision is worse with sunglasses or glare from reading lamps or fluorescent lights. Colors may appear changed. For example blue appears greenish, white is gray or beige (and its not your detergent) yellow appears white. These symptoms and signs can also be indicators of other eye problems so it is important to have your eyes tested every year or whenever you notice a change in the vision. Not every change in your vision is “just a sign I’m getting older.”
I hope you remembered to move your clocks ahead last night. If not, then there is a good reason why you are running an hour late for everything today.