Cataracts

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What Are Eye Cataracts?

Cataracts are a common eye condition in which the lens inside your eye becomes cloudy, causing blurry vision. Most people over 60 years of age develop some degree of cataracts. In many parts of the world, cataracts are a primary cause of avoidable blindness.

cataracts scaled e1598035826129

What Causes Cataracts? 

Behind the iris (the colored part of your eye) sits the crystalline lens, which is a clear structure that helps your eye focus light. Zonule fibers attach the lens to the ciliary muscle, which controls the curvature of the lens. 

When you read something up close, the lens becomes more rounded, allowing your eye to increase focus. When you look far away, the lens flattens out, allowing your eye to relax focus.

Early on in life, the lens is very flexible, allowing the ciliary muscle to easily control the lens. Over time, the natural aging process causes the lens to stiffen and thicken. Presbyopia, the loss of ability to see at near, occurs when the ciliary muscle has trouble flexing the stiffened lens. This process usually begins after age 40. 


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Over time, the proteins inside the lens also start to break down in a process called oxidation. Oxidation causes the lens to turn yellow and cloudy.

three main layers of the eye

Types of Cataracts

The crystalline lens is structured in multiple layers, much like an onion. Cataracts can form in the various layers, and you may have a combination of different types of cataracts. The three most common forms of age-related cataracts are:

  • Nuclear sclerotic cataracts are associated with the hardening and yellowing of the center of the lens, which is the nucleus. Typically, these cataracts progress slowly over several years or more. Many people maintain good vision until the cataracts are quite dense, eventually turning a brown color.
  • Cortical cataracts refer to the cortex, which are the layers surrounding the nucleus. The formation of cortical cataracts is similar to spokes on a wheel. The spokes can extend from the periphery of the lens, where they may not cause any visual symptoms. They tend to have a more significant impact on your vision once they grow towards the center of the lens. Some cortical cataracts develop over a few months, while others progress over several years.
  • Posterior subcapsular cataracts occur in the cortex's outermost layer, on the side closest to the back of your eye. These cataracts are more likely to occur in younger people as opposed to the other types. They also tend to grow more quickly and cause significant vision changes versus nuclear sclerotic cataracts.

Other Causes of Cataracts

Cataracts can form for other reasons besides age. They may be related to factors such as:

  • Diabetes. Diabetic cataracts can affect both younger and older people. When blood sugar levels are high, the crystalline lens absorbs excess sugar and fluid in the eye, leading to cataract formation. 
  • Medications. Steroids are a common cause of medication-induced cataracts and are often associated with posterior subcapsular cataracts. People taking high doses of steroids over long periods are at highest risk, and include those on oral, inhaled, or injected steroids. Other drugs that may increase your risk for cataracts include amiodarone (medication for irregular heartbeat), phenothiazines (antipsychotic medications), and certain antimalarial drugs.
  • Trauma or surgery. An eye injury or eye surgery can disrupt the lens, causing a cataract to develop. In some cases, if the zonule fibers are damaged, the lens can become dislodged, requiring prompt surgical repair. The cataract may form shortly after the incident, or long after the injury or surgery.
  • Congenital. These cataracts are present at birth. There may be a genetic component or underlying disease associated with congenital cataracts. In other cases, the cause is unknown. Some people with congenital cataracts do not experience significant vision problems. However, children with cataracts large enough to impair the vision can develop amblyopia (lazy eye) if they are not removed.

Common Signs & Symptoms of Cataracts

In many cases, mild cataracts do not cause any symptoms. Once cataracts start to progress, you may notice symptoms including:

  • Cloudy or blurry vision
  • Difficulty seeing in the dark
  • Increased glare and halos, particularly when driving at night
  • Light sensitivity
  • Difficulty reading, especially in dim light
  • Dark or blurry spots in your vision
  • Yellowing of colors, which may be more noticeable with white objects
  • Significant changes in your eyeglass prescription, particularly an increase in myopia (nearsightedness)
  • Double vision, even when one eye is closed

Treatment Options: How Are Cataracts Removed?

Not all cataracts need to be removed. If the cataract is mild and your vision is clear, most doctors will simply monitor your cataracts. If you develop symptoms, you can decide if you want to have them removed.

Cataract surgery is an outpatient procedure (does not require a hospital stay) and only takes about 20 minutes. Typically, the surgeon removes one cataract first. After your eye heals, they remove the cataract from your other eye, if necessary.

Cataract surgery involves a few general steps:

  • Removing the cataract involves a process called phacoemulsification. During this procedure, the surgeon inserts a small ultrasound device into your eye. The ultrasound waves break up the cataract, and a suction device vacuums the pieces out of your eye.

Laser-assisted cataract surgery is a modern technique that can replace some of the steps involved in removing the cataract. Instead of a surgical blade, the surgeon can use a laser to make an incision on your cornea. The laser can break up the cataract, which uses less energy and is less disruptive to the eye than phacoemulsification. 

  • Inserting an intraocular lens implant restores your vision to normal. The surgeon selects which implant to replace the cataract with based on your prescription. This implant is permanent and does not need to be replaced. There are many different lens implants available, including monofocal (mainly to see at a distance), multifocal (corrects distance and near vision), toric (corrects astigmatism), and many others. 

Common Questions & Concerns 

As we get older, many people become concerned with developing cataracts. These are some frequent questions regarding cataracts:

Are Cataracts Curable?

Yes, once your cataracts are removed, they do not grow back. 

However, a small percentage of people develop posterior capsular opacification after surgery. This condition is also called a secondary cataract or after-cataract. However, this opacification is not a new cataract. A posterior capsular opacification is a clouding of the membrane that is left in place during cataract surgery. This membrane is called the lens capsule and helps support the lens implant.

If enough clouding occurs, you may experience blurry vision. The eye surgeon can perform a procedure called posterior capsulotomy to restore your vision. This is a quick and painless treatment in which the surgeon uses a laser to create an opening in the lens capsule. 

Can Cataracts Be Prevented?

There is no proven regimen to prevent age-related cataracts. However, you may be able to slow down the progression of cataracts by:

  • Limiting sun exposure. Wear sunglasses outdoors, even on overcast days. Add a brimmed hat for more protection. 
  • Discontinuing cigarette use.  Smoking has been demonstrated to speed up cataract progression.
  • Eating foods with antioxidants. Studies show that antioxidants, particularly lutein and zeaxanthin, may combat the oxidation process involved in cataract formation. Many colorful fruits and vegetables contain eye-healthy antioxidants.

How Fast Do Cataracts Grow?

Cataracts form at different rates, so it is hard to predict how soon you may need surgery. Progression also depends on the type of cataract you have. Some cataracts develop over several years, or even decades. Other cataracts grow rapidly, over a few months.

Your health and lifestyle also have an impact on cataracts. For example, if you have diabetes or spend most of your day working outdoors, you may be more likely to develop cataracts.

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Author: Melody Huang, O.D. | UPDATED June 2, 2020
Resources

Chang, Jessica R., et al. “Risk Factors Associated with Incident Cataracts and Cataract Surgery in the Age-Related Eye Disease Study (AREDS).” Ophthalmology, vol. 118, no. 11, Nov. 2011, pp. 2113–2119., doi:10.1016/j.ophtha.2011.03.032.

Cumming, R. G., and P. Mitchell. “Medications and Cataract The Blue Mountains Eye Study.” Ophthalmology, vol. 105, no. 9, 1 Sept. 1998, pp. 1751–1758., doi:10.1016/s0161-6420(98)99049-2.

Dong, Xiuqin, et al. “Ultraviolet Radiation–Induced Cataract: Age and Maximum Acceptable Dose.” Investigative Opthalmology & Visual Science, vol. 44, no. 3, 1 Mar. 2003, pp. 1150–1154., doi:10.1167/iovs.02-0541.

Hejtmancik, J. Fielding, and Alan Shiels. “Overview of the Lens.” Progress in Molecular Biology and Translational Science Molecular Biology of Eye Disease, vol. 134, May 2015, pp. 119–127., doi:10.1016/bs.pmbts.2015.04.006.

Ma, Le, et al. “A Dose–Response Meta-Analysis of Dietary Lutein and Zeaxanthin Intake in Relation to Risk of Age-Related Cataract.” Graefes Archive for Clinical and Experimental Ophthalmology, vol. 252, no. 1, Oct. 2013, pp. 63–70., doi:10.1007/s00417-013-2492-3.

Pollreisz, Andreas, and Ursula Schmidt-Erfurth. “Diabetic Cataract—Pathogenesis, Epidemiology and Treatment.” Journal of Ophthalmology, vol. 2010, June 2010, pp. 1–8., doi:10.1155/2010/608751.

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