A cataract is a clouding of the normally clear lens inside the eye, affecting millions of people worldwide and gradually dimming the bright world around them. This common eye condition transforms everyday activities like reading a book, recognizing a friend’s face, or driving at night into significant challenges, yet effective treatment exists to restore vision and quality of life.

How Common Are Cataracts?

Cataracts represent one of the most widespread eye conditions affecting people across the globe. More than half of all Americans age 80 or older either have cataracts or have undergone surgery to remove them. This makes cataracts an almost inevitable part of aging for many individuals.^[2]

The condition affects people worldwide without discrimination. By the time someone reaches their 80s, most people will either be living with cataracts or will have already had them treated through surgery. Half of all Australians over the age of 50 are affected by cataracts, and by age 70 or 80, almost everyone develops them to some degree.^[6]

Cataracts remain the single most common cause of global blindness. In 2020, cataracts caused nearly 40 percent of all cases of blindness worldwide and contributed to over 28 percent of visual impairment cases globally.^[5] This widespread impact makes cataracts a significant public health concern, though the good news is that effective treatment is available.

Cataract surgery has become one of the most commonly performed operations in the United States. This reflects both the high prevalence of the condition and the success rate of surgical intervention in restoring vision. More than 3 million procedures are performed annually in the United States alone.^[10]

What Causes Cataracts?

Understanding what causes cataracts begins with knowing how the eye’s lens normally functions. When you’re young, the lens in your eye remains clear and flexible. This transparent structure sits behind the colored part of your eye (the iris) and helps focus light onto the retina at the back of your eye, much like a camera lens focuses an image.^[7]

The lens consists mostly of water and proteins called crystallins, which are proteins that help keep the lens clear and properly arranged. Around age 40, these proteins begin to break down and clump together. This process creates cloudy patches that start to affect your vision. Over time, the cataract grows larger and makes more of your lens cloudy, eventually leading to the vision problems people associate with cataracts.^[2]

The primary mechanism behind cataract formation involves oxidative stress, which means damage to lens proteins from harmful molecules in the body. This oxidative stress damages the lens proteins, causing them to stick together and form clumps. These clumps of protein or yellow-brown pigment accumulate in the lens, reducing the amount of light that can pass through to the retina and impairing vision. Additionally, changes in the lens’s metabolic processes, including imbalances in calcium and other important minerals, contribute to cataract development.^[5]

Most cataracts develop because of normal aging changes in the eyes. However, cataracts can also occur for other reasons. They may form after an eye injury, sometimes appearing years after the initial trauma. People who have had surgery for other eye problems, such as glaucoma (a condition involving increased pressure in the eye), may also develop cataracts as a secondary complication.^[2]

Radiation exposure represents another cause of cataracts. People who have undergone radiation treatment, particularly in the upper body area for cancer treatment, face an increased risk of developing cataracts. Some babies are even born with cataracts, a condition known as congenital cataracts, which may be inherited or develop shortly after birth.^[3]

Risk Factors for Developing Cataracts

While aging is the most significant risk factor for cataracts, with protein breakdown typically starting around age 40, several other factors can increase your likelihood of developing this condition. People typically don’t notice symptoms until age 60 or later, though certain medical conditions may cause symptoms to appear sooner.^[3]

Having diabetes significantly increases your risk of developing cataracts. People with diabetes often experience cataracts at a younger age than those without this metabolic condition. The elevated blood sugar levels associated with diabetes can affect the lens and accelerate cataract formation.^[2]

Lifestyle choices play an important role in cataract risk. Smoking tobacco substantially increases your chances of developing cataracts. Similarly, drinking too much alcohol over time contributes to cataract formation. Both of these habits introduce harmful substances into your body that can damage the delicate proteins in your eye’s lens.^[2]

If you have a family history of cataracts, your risk increases. Cataracts can run in families, suggesting a genetic component to their development. Past eye injuries, even those that occurred years ago, can lead to cataract formation later in life. People who have had previous eye surgeries or radiation treatment on their upper body also face elevated risk.^[2]

Long-term use of certain medications, particularly steroids (medicines used to treat conditions like arthritis or allergies), can increase your likelihood of developing cataracts. These medications affect the lens structure over time, making regular eye examinations especially important for people who need to take them for extended periods.^[2]

Additional risk factors identified in various studies include poor nutrition, obesity, chronic kidney disease, and autoimmune diseases. All of these conditions have been recognized as contributing factors to cataract development, highlighting how overall health impacts eye health.^[5]

Recognizing Cataract Symptoms

Cataracts typically develop slowly, and you may not notice any vision changes at first, particularly when cataracts are mild. The cloudiness in your vision caused by a cataract may initially affect only a small part of the eye’s lens, so you might not be aware of any vision loss in the early stages. However, as the cataract grows larger, it clouds more of your lens and causes more noticeable symptoms.^[1]

One of the hallmark symptoms of cataracts is clouded, blurred, or dim vision. People often describe it as feeling like they’re looking at the world through a dirty or fogged-up window. This cloudiness makes it more difficult to perform everyday activities such as reading, recognizing a friend’s face, or seeing details clearly.^[1]

Colors may appear faded or yellowed when you have cataracts. What once seemed bright and vibrant may now look dull or have a brownish or yellowish tint. This change in color perception happens because the clouded lens changes how light enters your eye and reaches the retina.^[2]

Many people with cataracts struggle with night vision. Seeing well after dark becomes increasingly challenging, and nighttime driving can be especially difficult. Street lamps, oncoming headlights, and other light sources may seem too bright or create uncomfortable glare. You might also see halos around lights, which appear as circles of light surrounding light sources.^[1]

Sensitivity to light and glare becomes problematic as cataracts develop. You may find that you need brighter lighting for reading and other activities, yet bright lights can also cause discomfort. This paradox occurs because the clouded lens scatters light differently, making both too little and too much light problematic.^[1]

Some people experience double vision in one eye due to cataracts. Interestingly, this double vision sometimes goes away as the cataract becomes larger and more dense. You may also find yourself needing frequent changes to your eyeglass or contact lens prescription as the cataract progresses and continues to affect your vision.^[2]

These symptoms typically worsen gradually over time, making it hard to read, drive, or carry out routine tasks. The gradual nature of vision loss means some people adapt to their declining vision without realizing how much their sight has deteriorated until they have it evaluated by an eye care professional.^[3]

Preventing Cataracts

While you cannot completely prevent age-related cataracts since they result from normal aging changes, you can take several steps to protect your eyes and potentially slow their development. These preventive measures focus on reducing risk factors that contribute to cataract formation.^[2]

Protecting your eyes from the sun stands as one of the most important preventive actions you can take. Wearing sunglasses with UV protection and a hat with a brim when you’re outdoors helps block harmful ultraviolet light from reaching your eyes. This simple measure protects your eyes from the cumulative damage that UV light causes over time.^[2]

Protecting your eyes from injury is equally important. When doing activities that could harm your eyes, such as using power tools, playing certain sports, or working with chemicals, always wear appropriate protective eyewear. Eye injuries can lead to traumatic cataracts, sometimes years after the initial injury occurred.^[2]

Maintaining a healthy lifestyle may help slow cataract progression. Fresh fruits and vegetables contain nutrients vital to maintaining healthy eyes. While this approach cannot cure or completely stop cataract development, some studies have shown that a healthier lifestyle may slow the condition’s advancement. A diet rich in antioxidant vitamins and minerals supports overall eye health.^[16]

If you smoke, quitting represents one of the most beneficial actions you can take for your eye health. Smoking significantly increases your risk of developing cataracts and causes them to progress more rapidly. Similarly, limiting alcohol consumption helps protect your eyes from cataract formation.^[2]

Regular eye examinations allow for early detection and monitoring of cataracts. If you’re over 40 years old, seeing your optometrist for routine eye tests becomes increasingly important. These examinations can catch cataracts in their early stages and help your eye doctor track any changes to your vision over time.^[6]

How Cataracts Change Normal Eye Function

To understand how cataracts affect vision, it helps to know how the eye normally works. The lens of your eye is a clear, flexible structure located behind the iris and pupil. It functions much like a camera lens, focusing light onto the retina at the back of your eye, where the image is recorded and then transmitted to your brain through nerve signals.^[7]

The lens is composed of several layers. In the center sits the nucleus, similar to the core of an apple. Surrounding the nucleus is the cortex, which is like the fruit you eat around the apple’s core. Covering everything is the lens capsule, a thin membrane that protects the lens, comparable to an apple’s skin.^[3]

When cataracts form, the normally transparent lens becomes cloudy. This cloudiness occurs because the proteins in the lens, which are usually arranged in a precise way to keep the lens clear, begin to break down and clump together. These protein clumps create cloudy areas that interfere with how light passes through the lens.^[7]

As the lens becomes cloudier, less light can pass through it to reach the retina. The light that does get through is scattered rather than properly focused, resulting in blurred or distorted vision. Think of it like trying to see through a window that has become increasingly foggy or dirty. The retina cannot receive a clear, sharp image, so the signals it sends to your brain produce unclear vision.^[1]

The lens also adjusts the eye’s focus, allowing you to see things clearly both up close and far away. When cataracts develop, this focusing ability becomes impaired. The clouding and yellowing of the lens changes how it bends light, affecting your ability to see at different distances and altering your perception of colors.^[7]

Different types of age-related cataracts affect different parts of the lens. A nuclear sclerotic cataract forms in the nucleus at the center of the lens. A cortical cataract develops in the cortex surrounding the nucleus. A posterior subcapsular cataract forms in the back part of the cortex, just beneath the lens capsule. People often develop more than one type at the same time, as cloudy patches commonly form in multiple areas of the lens.^[3]

These changes in lens structure and function happen gradually. The accumulation of protein clumps and yellow-brown pigment in the lens reduces light transmission progressively over time. Additionally, alterations in the lens’s metabolic processes, including imbalances in calcium and other ions, contribute to the ongoing development of cataracts and the continued deterioration of vision.^[5]