What is a Cataract?
A cataract is a clouding of the eye’s lens that causes a progressive, painless loss of vision. Although this eye disease is the leading cause of blindness worldwide, the exact cause of cataracts is still unknown. Many experts believe there are a number of contributing factors, such as age, illness, injury, or certain medications. According to the National Eye Institute, “By age 80 more than half of all Americans either have a cataract or have had cataract surgery.”
Cataracts typically develop in one eye, but people who have had a cataract in one eye are more likely to develop one in the other eye at some point. Sometimes cataracts develop in both eyes at the same time.
In a normal eye, light enters the eye and passes through the lens. Colors are vibrant, images are clear, and the eyes are able to adjust to changes in lighting. When a cataract is present, images are distorted or blocked altogether, and colors seem dull and more yellow. Most people notice that their vision becomes blurry when they begin to develop cataracts.
Types of Eye Cataracts
- Age-related cataracts: Protein builds up in the lens and causes cloudiness or discoloration of the lens.
- Secondary cataract: Forms after surgery for other eye disease like glaucoma or diabetic retinopathy
- Traumatic cataract: Forms after eye injury
- Congenital cataract: Present at birth due to birth defects, diseases, or other problems
- Radiation cataract: Forms after severe radiation exposure
- Nuclear cataract: Forms in the center of the lens
- Posterior Subcapsular cataract: Forms in the back of the lens
Symptoms of cataracts can vary from one person to another, depending on the type of cataract they have. Symptoms for all types of cataracts may include blurry vision or glare from car headlights, especially at night. Sunlight or indoor overhead lighting may seem to be too bright or cause glare. You may notice that bright colors appear dull. You may also notice everything seems to be slightly yellow. Sometimes cataracts can cause double vision, and you may find that you are frequently changing contact lens or eyeglasses prescriptions. The degree of vision change depends on the intensity of the light entering the eye and the location of the cataract. As an example, let’s discuss a centrally located cataract for a minute.
Normally the pupil constricts in bright light, narrowing the pathway through which light enters the eye. When a cataract is present, the light has a difficult time passing through the cataract, especially when it is centrally located (this is called a nuclear cataract). When it is dark, the pupil dilates, which causes bright lights that suddenly appear in the darkness (such as headlights approaching on a dark road) to scatter at the edge of the cataract, causing glares and halos. When a cataract develops in the back of the lens (a posterior subcapsular cataract) it affects a person’s vision more than a cataract in another location because the cloudiness is at a point where the light rays are already focused in a narrow beam. The effect of going from brightly lit rooms into dark ones can be more extreme and cause an even greater loss of vision. The severity of the symptoms can depend on the location of the cataract.
Occasionally you may experience cataract-like symptoms, but those symptoms may be a sign of another eye-related problem. This is why it is advisable to see your eye doctor if you are experiencing any changes in your vision.
The eye doctor will put drops in your eyes to dilate your pupils and then perform a thorough eye exam. He or she will study the crystalline lens of your eye and check the optic nerves and retina for changes that may be contributing to your vision problems. This is typically done with an ophthalmoscope, which is a handheld tool used to look inside the eye. Using an instrument called a slit lamp, your eye doctor can identify the location of the cataract and determine its severity. The eye doctor may also perform a tonometry test in order to measure the pressure inside your eye. This is one of the diagnostic tools for glaucoma.
What Causes Cataracts?
The lens of an eye is made up of water and protein. The protein is arranged in a way that keeps the lens clear and allows light to pass through. A cataract forms when some of the protein clumps together and begins to cloud a portion of the lens. Over time it grows larger and affects your vision. Although the exact cause of cataracts remains a mystery, many experts believe it has to do with the aging process. In the United States, 20 percent of people between the ages of 65 and 74 develop cataracts severe enough to reduce their vision, and almost half of all people over 75 have cataracts. Cataracts seem to be more common when age is coupled with:
- Malnutrition or poor eating habits
- Exposure to certain drugs, such as corticosteroids, for long periods
- Exposure to ultraviolet light over long periods
- Exposure to x-rays for long periods
- Darker eyes
- Alcohol use
- Intrauterine infection during the first trimester of pregnancy
- Surgery for other eye problems
- Injury to the eye (cataracts can develop many years after an injury)
- Family history of cataracts
There are also several diseases that can cause cataracts or increase the risk of developing them. These include:
- Down’s syndrome
- Werner’s syndrome
- Atopic dermatitis
- Myotonic dystrophy
- Occult tumors (e.g., choroidal melanoma in adults and retinoblastoma in children)
The only effective treatment for cataracts is to have them surgically removed. Modern cataract surgery is one of the most frequently performed surgical procedures in the United States, and it has a greater than 95 percent success rate when performed by an experienced cataract and lens implantation surgeon. Many people compare the physical impact of cataract surgery to having a tooth extracted.
Surgery is almost always performed under local anesthesia, and only the eye’s surface is numbed, either by injection or eye drops. If the patient cannot hold still for the surgery—as young children often cannot—general anesthesia may be used, but these situations are rare.
Cataract surgery usually requires the replacement of the natural lens with an intraocular lens (IOL). The cloudy natural lens is replaced with a clear IOL, thereby giving you better vision. Today’s ophthalmologists can actually replace the cloudy lens with a technologically advanced intraocular lens such as Crystalens® or ReSTOR®, which will correct not only your distance vision but your near- and arm’s-length vision as well. These are more similar to the natural lenses you had when you were younger, and can restore the up-close vision you lost in your forties, when you became presbyopic.
There are two types of cataract surgery used today. They are called phacoemulsification and extracapsular surgery. In phacoemulsification, or “phaco” for short, a tiny incision is made in the cornea, and a computer-assisted device emits ultrasound waves to break the lens into tiny pieces. The pieces are then removed and replaced with an IOL. In extracapsular surgery, a longer incision is made, and the cloudy core of the lens is removed as a whole piece while any leftover parts of the lens are sucked up. Complications of cataract surgery are unusual, but may include infection, bleeding, pain, swelling, and sometimes something called an “after-cataract.” This is a condition in which tissue surrounding the IOL becomes cloudy. Fortunately, an eye surgeon can easily eliminate the after-cataract by using a laser, without any additional surgery. This procedure, called a YAG laser capsulotomy, is extremely effective and relatively quick and simple.
In the vast majority of cases, cataract surgery and lens implantation is performed in an outpatient setting, meaning that you will be able to go home within a few hours of having your cataract removed and a new lens implanted. You can generally expect to be able to resume your normal work and recreational activities within a few days.
After Cataract Surgery
Almost immediately after surgery, patients are able to see and resume their everyday activities. Arrangements do need to be made for a ride home following the procedure, however, and many doctors recommend having someone around for a few days following the procedure because activities may be restricted. For example, for about a week after cataract surgery you are not allowed to bend over and pick up heavy objects, lest you elevate pressure in the eye during the post-operative healing phase.
Your doctor will make an appointment to see you the day after cataract surgery and a few more times after that to check up on your healing process. During this time you should be careful not to put any pressure on the eye by rubbing your eyes or bending over as described above.
Because of the surgery and eye drops, you may have fluid discharge. Some people may experience pain, discomfort, or itchy eyes. Your doctor may give you medication to help relive these symptoms. Typically you are given eyeglasses or a metal shield to wear to protect the eye from injury until healing is complete, usually within a few weeks. For people who have cataracts in both eyes, most doctors wait two to four weeks for the first eye to heal before performing surgery on the other eye
Most people notice an improvement in their distance vision within a few days or weeks after surgery. Unless an advanced-tech IOL, (i.e., a multifocal) is implanted, most people who undergo cataract surgery will need eyeglasses for reading, and some will still need eyeglasses to obtain the best possible distance vision as well.
Cataract Surgery Complications
Thankfully, complications after cataract surgery are rare, but they do occur in some people. The most common complication following cataract surgery is the development of haziness in the tissue behind the eye where the original lens was removed (this is called a secondary cataract). Approximately one in four people who undergo cataract surgery experience this problem. It can develop months or even years later, but always after an artificial lens is implanted. Typically, treatment involves using a laser to make a small opening to let light through. Additional cataract surgery complications may include:
- Pressure in eye (if left untreated, glaucoma could develop)
- Macular edema (swelling)
- Bleeding in eye
- Persistent corneal edema
- Implant becomes dislocated
- Loss of vision
On rare occasions, more specifically in those with retinal disorders such as diabetic retinopathy, vision worsens after the surgery. Proper care after surgery can prevent major complications from developing.
Although cataracts develop in most people as they age, there are several things you can do while you are young to try to prevent them. If you look again at the list of causes of cataracts, you will find that many of the items listed can be avoided. For example, exposure to too much sunlight can increase your chances of developing cataracts later in life, but if you wear sunglasses that have a protective coating against ultraviolet rays, you can protect your eyes from the harmful effects of sunlight exposure. Additional steps you can take to prevent or reduce the risk of cataracts include:
- If you have another disease such as diabetes, talk with your doctor to ensure that your condition is well controlled. In cases of diabetes, blood sugar levels would need to be controlled.
- Make sure to get enough vitamin C, vitamin A, and carotenoids, which are found in leafy green vegetables such as kale and spinach.
- If you are a woman, talk with your doctor about taking estrogen after menopause.
- Talk with your doctor about changing any medications you have been taking for a long time, especially corticosteroids.
- Get regular or annual eye examinations, especially after the age of 40.
Facts About Cataracts
Cataracts are the leading cause of blindness in the world. Here are some interesting statistics and facts about this common eye disease:
- 400 out of 100,000 newborns are affected by congenital cataracts.
- 5,000 out of 100,000 people aged 52–62 are affected by cataracts.
- 92,000 out of 100,000 people aged 75–85 are affected by cataracts.
- 46,000 out of 100,000 people aged 75–85 have significant vision loss (20/30 or worse)
- A third of congenital cataracts are inherited.
- 10 percent to 38 percent of childhood blindness is attributable to cataracts.
- People who live at higher altitudes and in climates with high levels of ultraviolet radiation (such as in Tibet) are at an increased risk of developing cataracts.
- Surgery is more than 95 percent successful in restoring the vision of people who have age-related cataracts and no other eye disease.
- Blindness occurs in approximately 1 percent of people with cataracts, even after treatment has been sought.
Did You Know … cataracts can develop within days of an electrical shock or after being struck by lightening.
- MDConsult Cataract http://www.mdconsult.com/das/pdxmd/body/244164197-3/0?type=med&eid=9-u1.0-_1_met_1014153
- M. Beers, MD “The Merck Manual of Medical Information” 2nd home edition (Pocket Books, 2003) 1303-1305
- S. Moore, MD, K. Yoder, MD “Complete Guide to Symptoms, Illness, & Surgery) Revised 5th edition (The Berkeley Publishing Group, 2006) 125: 208
- M. Lipner Femto technology changing the cataract landscape http://eyeworld.org/article.php?sid=5674&strict=&morphologic=&query=cataracts