What Are Cataracts?

Eye with a Cataract

What is a Cataract?

Your eye works a lot like a camera. Light rays focus through your lens onto the retina at the back of the eye. Similar to photographic film, the retina allows the image to be “seen” and interpreted by the brain. Over time, the lens of our eye can become cloudy, preventing light rays from passing clearly through the lens. The loss of transparency of the lens may be so mild that vision is barely affected, or it can be so severe that no shapes or movements are seen. When the lens becomes cloudy enough to obstruct vision to any significant degree, it is called a cataract.

What Causes Cataracts?

Aging is the most common cause of cataracts. Cataracts are very common, affecting roughly 60% of people over the age of 60. Other causes include trauma, medications such as steroids, systemic diseases such as diabetes, and prolonged exposure to ultraviolet light. Sometimes babies can be born with cataracts, called congenital cataracts.

As you age, the lenses in your eyes become less flexible, cloudy and thicker. Age-related changes 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 larger portion of the lens surface.

Cataracts usually develop in both eyes. However, cataracts are usually not completely symmetrical, as the cataract in one eye may be more advanced than the other. There are also different types of cataracts that can have different appearances and may be caused by reasons other than typical aging.


Cataracts usually form slowly and cause few symptoms until they noticeably disturb or block light.

Symptoms can include:

  • Vision that is cloudy, blurry, foggy, or filmy
  • Changes in color saturation (fading or yellowing)
  • Glare or halos, particularly at night
  • Double vision (like a superimposed image)
  • Sudden or frequent changes in the strength of glasses prescription

Treatment Options

Cataract surgery is a very successful operation and generally has excellent outcomes with improvement in the quality of vision. One and a half million people have this procedure every year and the vast majority of patients have a successful result. As with any surgical procedure, complications can occur during or after surgery and some are severe enough to limit vision. In most cases, vision, as well as the quality of life, improve significantly with this relatively quick and painless outpatient procedure.