What is a Cataract?
A cataract is a clouding of the lens in the eye. Most cataracts are related to exposure to ultraviolet light and aging. However, people can have an “age-related” cataract in their 40’s and 50’s. During middle age, most cataracts are small and do not affect vision. It is after age 60 that most cataracts will begin to cause problems with a person’s vision.
The lens is a clear part of the eye that helps to focus light on the retina. In a normal eye, the light passes through the lens to the retina. Once it reaches the retina, the 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 in cloudy from a cataract, the image seen will be blurred.
Most cataracts develop slowly and aren’t very noticeable in the early stages. But with time, cataracts will eventually interfere with vision. At first, stronger lighting and change in eyeglass prescription can help with cataracts. But as cataracts progress, and impaired vision interferes with normal daily activities, surgery may be necessary. Fortunately, cataract surgery is generally a safe, effective procedure.
Symptoms:
Clouded, blurred or dim vision
Increasing difficulty with night vision
Sensitivity to light and glare
Need for brighter light
“Halos” around lights
Frequent changes in eyeglass prescription
Fading or change in color perception
Double vision in a single eye
Types of Cataracts:
Nuclear Cataract
A nuclear cataract forms deep in the central zone (nucleus) of the lens. These cataracts are usually associated with aging. With a nuclear cataract the lens begins to yellow and cloud vision. At first this may cause more nearsightedness or even a temporary improvement in near vision. But with progression, the lens turns darker yellow or even brown, which will cause increased blur and can lead to difficulty distinguishing between shades of color.
Cortical Cataract
A cortical cataract is often characterized by spoke-like opacities that start in the periphery of the lens and work their way into the center. This type of cataract occurs in the lens cortex, the area surrounding the nucleus. As this cataract progresses, it can interfere with light rays passing through the lens causing more glare.
Posterior Subcapsular Cataract (PSC)
A PSC starts as a small, opaque area that usually forms near the back of the lens, right in the path of light. A PSC often interferes with reading, reduces vision in bright light, and can cause glare and halos around lights at night. This type of cataract often progresses faster than other types do. People with diabetes or those taking high doses of steroid medications have a greater risk of developing these cataracts.
Although most cataracts are related to aging, there are other types of cataract. These include traumatic cataract, which develop after an eye injury, congenital cataract, radiation cataract, or secondary cataracts which can form after surgery for some other eye problem (ie. retinal detachment).
Causes of Cataracts:
The lens lies behind the iris and the pupil. It works much like 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, resulting in sharp vision both up close and far away. The lens is made of mostly water and protein. The protein is arranged in a precise way that keeps the lens clear and allows light to pass through. With aging, the protein begins to clump together and clouds the lens. This is a cataract. As time passes, the cataract grows larger and can cloud more of the lens, making it harder to see.
These clumps of protein can reduce the clarity of an image reaching the retina. A cataract scatters and blocks the light as it passes through the lens. The clear lens slowly changes to a yellowish/brownish color, adding a yellow tint to vision. With advanced lens discoloration, it may be difficult to identify blues and purples.
Risk Factors:
Increasing age
Excessive exposure to sunlight
Diabetes
Smoking
Obesity
High blood pressure
Previous eye injury or inflammation
Previous eye surgery
Prolonged use of steroid medications
Excessive alcohol intake
Prevention:
Although there is significant controversy about whether or not cataracts can be prevented, there are several actions that may be helpful.
Wear sunglasses
Quit smoking
Reduce alcohol use
Manage other health problems
Follow treatment plans as outlined by primary care physicians, especially if diabetic
Eat a healthy diet
There are various studies which show that antioxidants and supplements such as Vitamin E, Vitamin C, Omega 3 fatty acids, and lutein/zeaxanthin were associated with decreased risks of cataract. In general, green, leafy vegetables and fruits, especially berries, are high in antioxidants which help maintain the health of the eye.
Treatment:
The symptoms of an early cataract may be improved with a change in glasses prescription, stronger magnification for reading, brighter lighting, or anti-glare coatings/materials. If these measures do not help, it may be time to think about surgical intervention. A cataract needs to be removed when vision loss interferes with everyday activities, such as driving, reading, or watching TV. Surgery involves removing the cloudy lens and replacing it with an artificial one. Sometimes a cataract is removed even when it does not cause problems with vision. For example, a cataract may be removed if it interferes with a doctor’s ability to examine or treat another eye problem, such as age-related macular degeneration or diabetic retinopathy.
Cataracts are detected at a comprehensive dilated eye exam. At that exam, the doctor can discuss the risks and benefits involved in cataract surgery and a decision can be reached as to whether or not to proceed with surgery. If both eyes require surgery, the surgery is performed on each eye at separate times, usually 1-2 weeks apart. Cataract removal is one of the most common operations performed in the United States. It is also one of the safest and most effective types of surgery. In about 90 percent of cases, people who have cataract surgery have better vision afterward.
The artificial lens that is placed in the eye is called an intraocular lens (IOL). New IOL’s are constantly being developed that make the surgery less complicated for surgeons and the lenses more helpful to patients. There are single vision IOL’s that attempt to correct a patient’s vision at a desired distance, presbyopia-correcting IOL’s that can potentially correct vision at all distances, and IOL’s that block ultraviolet and blue light rays, which research indicates may damage the retina.
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