A cataract is a clouding of the normally clear lens of your eye. Most cataracts develop slowly and don’t disturb your eyesight early on. But with time, cataracts will eventually interfere with your vision.
A cataract causes a part of the lens to become opaque, or cloudy. Light does not pass through easily, and vision becomes blurry.
Signs and symptoms of cataracts include:
- Clouded, blurred or dim vision
- Increasing difficulty with vision at night
- Sensitivity to light and glare
- Need for brighter light for reading and other activities
- Seeing “halos” around lights
- Frequent changes in eyeglass or contact lens prescription
- Fading or yellowing of colors
- Double vision in a single eye
- Reading becomes difficult and eventually impossible
At first, the cloudiness in your vision caused by a cataract may affect only a small part of the eye’s lens and you may be unaware of any vision loss. As the cataract grows larger, it clouds more of your lens and distorts the light passing through the lens. This may lead to more noticeable symptoms.
Cataracts often affect both eyes, but rarely equally.
Most cataracts develop when aging or injury changes the tissue that makes up your eye’s lens.
Some inherited genetic disorders that cause other health problems can increase your risk of cataracts. Cataracts can also be caused by other eye conditions, past eye surgery or medical conditions such as diabetes. Long-term use of steroid medications, too, can cause cataracts to develop.
The lens is made mostly of water and protein. Specific proteins within the lens are responsible for maintaining its clarity. Over many years, the structures of these lens proteins are altered, ultimately leading to a gradual clouding of the lens. Rarely, cataracts can present at birth or in early childhood as a result of hereditary enzyme defects, and severe trauma to the eye. Other factors that may lead to development of cataracts at an earlier age include excessive ultraviolet-light exposure, diabetes, smoking, or the use of certain medications. Exposure to radiation therapy leads to cataract.
HOW A CATARACT FORMS?
The lens, where cataracts form, is positioned behind the iris. The lens focuses light that passes into your eye, producing clear, sharp images on the retina. As you age, the lenses in your eyes become less flexible, less transparent and thicker. Age-related and other medical conditions cause tissues within the lens to break down and clump together, clouding small areas within the lens.
As the cataract continues to develop, the clouding becomes denser and involves a bigger part of the lens. A cataract scatters and blocks the light as it passes through the lens, preventing a sharply defined image from reaching your retina. As a result, your vision becomes blurred.
TYPES OF CATARACTS
Cataract types include:
- Nuclear cataracts affect the center of the lens
- Cortical cataracts affect the edges of the lens
- Posterior subcapsular cataracts affect the back of the lens
- Congenital cataracts are present from birth
- Secondary cataracts are caused by disease or medications. Diseases that are linked with the development of cataracts include glaucoma and diabetes. The use of the steroid prednisone and other medications can sometimes lead to cataracts.
- Traumatic cataracts develop after an injury to the eye, but it can take several years for this to happen.
- Radiation cataracts can form after a person undergoes radiation treatment for cancer.
Factors that increase your risk of cataracts include:
- Increasing age
- Excessive exposure to sunlight
- High blood pressure
- Previous eye injury or inflammation
- Previous eye surgery
- Prolonged use of corticosteroid medications
- Drinking excessive amounts of alcohol
To determine whether you have a cataract, your doctor will review your medical history and symptoms, and perform an eye examination. Your doctor may conduct several tests, including:
Visual acuity test: A visual acuity test uses an eye chart to measure how well you can read a series of letters. Your eyes are tested one at a time, while the other eye is covered. Using a chart or a viewing device with progressively smaller letters, your eye doctor determines if you have 20/20 vision or if your vision shows signs of impairment.
Tonometry: A standard test to measure fluid pressure inside the eye
Slit-lamp examination: A slit lamp allows your eye doctor to see the structures at the front of your eye under magnification.
Contrast sensitivity testing. This checks for your ability to differentiate different shades of gray, which is often this limited by cataracts.
Retinal exam: To prepare for a retinal exam, your eye doctor puts drops in your eyes to open your pupils wide (dilate). This makes it easier to examine the back of your eyes (retina). Using a slit lamp or a special device called an ophthalmoscope, your eye doctor can examine your lens for signs of a cataract.
When your prescription glasses can’t clear your vision, the only effective treatment for cataracts is surgery.
The most common form of cataract surgery today is a process called phacoemulsification. With the use of an operating microscope, your surgeon will make a very small incision in the surface of the eye in or near the cornea. A thin ultrasound probe is inserted into the eye that uses ultrasonic vibrations to dissolve the clouded lens. These tiny fragmented pieces are then suctioned out through the same ultrasound probe. Once the cataract is removed, an artificial lens is placed into the same thin capsular bag that the cataract occupied. This intraocular lens is essential to help your eye focus after surgery.