Cataracts 
Richard L. Lindstrom, M.D. 

Definition:
A cataract is a clouding of the normally clear crystalline lens of the eye. The lens is normally extremely clear, and allows light to pass through and be focused onto the retina. When the lens is not clear, and light is impeded from passing through it, a cataract is said to be present in the lens. The term “cataract” comes from the Latin word for waterfall (cataracta) as very advanced cataracts may look white, like foamy water, and be visible to an observer with the naked eye.

Causes of cataracts:
Cataracts occur due to changes in the protein structure and water content of the crystalline lens. Normally, the crystalline lens, due to its highly ordered arrangement of specialized proteins and water, is very clear. Many processes, however, may cause changes in these proteins, which result in loss of clarity of the lens.

Aging:
By far the most common cause of cataract is aging. Almost everyone will develop some degree of cataract as they become older, with more than 70% of people over age 75 having some degree of these lens changes. As many older people with cataracts suffer a decline in vision from their cataracts, cataract surgery is often required to restore visual function. In fact, as 1.3 million cataracts are surgically removed each year in the United States, cataract surgery is one of the most common surgical procedures in the United States today. The exact reason why cataracts commonly appear with age is not well understood by scientists. Nuclear Sclerosis and Cortical Spoke cataracts are commonly associated with aging.

Medications:
Several medications can cause cataract with long-term use. The most common medications causing cataract are corticosteroids. These medications, often referred to simply as “steroids,” are used by doctors to treat many illnesses and diseases. Asthma and rheumatoid arthritis are two such diseases that often require long-term steroid use. Steroid associated cataracts are often Posterior Subcapsular cataracts. Long-term use of the eye medication pilocarpine can also cause cataracts to form.

Injury:
Any severe injury to the eye can result in the formation of a traumatic cataract. These cataracts almost always form if a foreign object has penetrated the eye and directly damaged the lens. They can also form after severe blunt injury to the eye, in which the eye briefly collapses.

Prior eye surgery:
Eye surgery for reasons other than cataract removal can occasionally result in the formation of a cataract. Rarely, this occurs due to damage of the crystalline lens during the surgery itself from instruments or lasers. Usually, however, cataracts may form slowly after eye surgery. Scientists believe this is due to an alteration in the way eye fluid moves within the eye after eye surgery is performed. Such alterations in eye fluid movement are common in retinal and glaucoma surgery, and, as such, cataracts may occur after these procedures.

Congenital Cataracts:
Congenital cataracts are present at birth and due to an abnormal formation of the lens while in the womb. Typically, these cataracts do not worsen with time, but occasionally can result in marked decreased vision for the infant. In such cases, babies undergo cataract surgery to allow them to see more normally as they age. Most congenital cataracts, however, do not cause significant decrease in vision and can be left in the eye without any problem.

Cataracts associated with other diseases:
Several other bodily diseases can cause cataracts to form. Diabetes is the disease most commonly associated with cataracts. Diabetes associated cataracts typically look like age related cataracts, but may form much sooner due to the diabetes. Some diabetic individuals need cataract surgery by their 30s or 40s, rather than 60s or 70s as is usual for age-related cataracts. Rare diseases, such as Wilson’s disease and myotonic dystrophy are also associated with cataracts. Long-term eye inflammation, such as uveitis, may also cause cataracts to form.

Symptoms (What you may experience if you have a cataract):
Cataracts can cause many visual symptoms. Most commonly, a decline in the sharpness of vision is noted. Some cataracts, such as Cortical or Posterior Subcapsular cataracts, can cause glare symptoms in bright light settings, such as outside on a sunny day. Nuclear sclerotic cataracts, in particular, can cause a decline in the crispness of colors, causing them to appear much more muted than before. Occasionally, cataracts can cause double vision to occur in the eye with the cataract, as the clouded portion of the lens may split the light into two images. Some older people, who have already entered presbyopia and have lost the ability to see clearly up close, may notice a return of their close vision as their cataracts grow. This condition, sometimes referred to as “second sight,” results from a change in the refractive power of the crystalline lens, caused by the cataract. Typically, though, the increased near vision comes at the price of decreased sharpness, glare and/or loss of crisp color sensation.

Examination for cataracts:

Tests you may have at the doctor’s office:
To determine if you have a cataract, your eye doctor will perform an eye evaluation. Your visual acuity will be measured, as well as your refraction. Sometimes, a “brightness acuity test” will also be performed to determine how well you see in bright light conditions. Often, if a cataract is present, the visual acuity tested by the brightness acuity test will be significantly worse than the visual acuity measured in a dark room. Other tests may include eye pressure measurement, pupil testing, a peripheral vision check and range-of-motion testing of the eye muscles. Your eyes may be dilated to help the doctor view the lens and the back part of the eye. Your doctor will perform a slit lamp examination to examine the eye and the lens. A retinal exam may also be performed during the dilated examination.

What your doctor sees in your eye if you have cataracts:
The loss of clarity of the lens, or cataract, typically occurs in one of 3 patterns, which are visible to your doctor during a slit lamp examination.

Nuclear sclerosis:
The center of the lens, or nucleus, progressively hardens, or scleroses, with age. This hardening may cause the nucleus to turn a yellow color, resulting in decreased vision. Nuclear sclerosis is one of the most common forms of age-related cataract. In addition to decreasing the sharpness of vision, it often causes colors to look more muted and one’s eyeglasses prescription to change markedly over time. Nuclear sclerosis cataracts usually progress slowly, taking several years to cause noticeable change in the vision. .

Cortical spokes:
The cortex, the softer lens material that surrounds the firmer central nucleus. Cortical cataracts appear white and “spoke-like.” Extremely advanced cortical cataracts can make the entire lens look white. Cortical spokes can cause decreased vision as well as glare in bright light settings. Even small cortical spokes, if they extend into the central vision area of the lens, can cause such visual symptoms.

Posterior Subcapsular Cataract:
Sometimes, changes in the lens occur at the far backside of the lens in the posterior subcapsular region. This area, which lies directly next to the lens capsule, the structure which helps hold the lens in place, can turn a hazy grey color from plaque-like abnormal lens cells, resulting in decreased vision. Marked glare symptoms may also occur in bright light settings. Occasionally, posterior subcapsular, or “PSC” cataracts can progress rapidly, and may compromise vision over a few short months.