A cataract is a cloudy or opaque area in the eye's natural lens. By age 80, more than half of all Americans either have a cataract or have had cataract surgery. A cataract can occur in either or both eyes but cannot spread from one eye to the other. It is the most common cause of vision loss in people over age 40 and is also the principal cause of blindness in the world.

Cataract Signs and Symptoms

At first, a cataract may have little effect on your vision. You may notice your vision is a little blurred, as though you were looking through glass. Symptoms may increase over time, and can include:

• Colors look duller and less bright. You may confuse black and purple, for example.
• Headlights, lamps, or sunlight may appear too bright. A halo may appear around lights.
• Poor night vision.
• Double vision or multiple images in one eye.
• Frequent prescription changes in your eyeglasses or contact lenses.

Normal vision, top.  Vision with cataracts, bottom.  Images from https://nei.nih.gov/

Types of Cataracts

The lens is composed of layers, like an onion. The outermost is the capsule. The layer inside the capsule is the cortex, and the innermost layer is the nucleus. A cataract may develop in any of these areas. Cataracts are named for their location in the lens:

• A nuclear cataract is in the center of the lens. The nucleus tends to darken, changing from clear to yellow and sometimes brown.
• A cortical cataract affects the layer of the lens surrounding the nucleus. The cataract looks like a wedge or a spoke.
• A posterior capsular cataract is found in the back outer layer of the lens. This type often develops more rapidly.

What Causes Cataracts?

The lens in your eye is mostly made of water and protein. The protein is arranged in a precise way that keeps the lens clear and lets light pass through it.

As we age, some of the protein may clump together and start to cloud a small area of the lens. This is a cataract, and over time, it may grow larger and cloud more of the lens, making it harder to see.

Besides advancing age, cataract risk factors include:

• Ultraviolet radiation
• Diabetes
• Hypertension
• Obesity
• Smoking
• Prolonged use of corticosteroid or statin medications
• Significant alcohol consumption

How Is a Cataract Diagnosed?

Cataracts are diagnosed through a comprehensive eye examination by your ophthalmologist. This examination may include:

1. Visual acuity test. This eye chart test measures how well you see at various distances.
2. Evaluation of the lens under high magnification and illumination to determine the extent and location of any cataracts
3. Dilated eye exam. Drops are placed in your eyes to widen, or dilate, the pupils. Your eye care professional uses a special magnifying lens to examine your retina and optic nerve for signs of damage and other eye problems.
4. An instrument measures the pressure inside the eye. Numbing drops may be applied to your eye for this test.

We are equipped to handle all of these and other tests to fully diagnose your condition. If it’s been a while, or if you have noticed a decrease in your vision, please call us to set up a time for an exam.

Next month we’ll look at the treatments available for Cataracts. Did you know that it’s possible to correct your cataracts and eliminate the need for glasses or contacts? Watch for our next post!

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