What Causes Cataracts?

Most often, cataracts are due to normal eye changes that occur with aging. Other potential causes include genetics, physical injury, continuous eye exposure to UV light, and underlying diseases like diabetes. 

Different Causes for Different Types of Cataracts

Cataracts often affect people during the advanced ages in life, and they manifest as clouded or blurred vision. Cataracts are protein membranes that gradually form in the eye lens, leading to the eyes’ reduced or distorted light perception.

Usually, they occur gradually and can be fully treated by ophthalmologists if diagnosed early enough.

Worldwide, it is estimated that over 15 million people over the age of 50 suffered from blindness due to cataracts in 2020 alone, which represented a 30 percent increase in 10 years. Moreover, another 78.8 million people reported moderate or severe vision impairment due to cataracts.

Below, we will look at the different forms of cataracts and what causes them.

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Types of Cataracts & Their Causes

There are different types of cataracts with a wide range of causes and treatments. 

Nuclear sclerotic cataracts

This is the most prevalent form of cataracts. They affect almost everyone who lives to old age. With nuclear sclerotic cataracts, the cataract will gradually form in the eye’s nucleus.

At some point, your eyesight will appear to improve for a short period, after which the lens will get denser and acquire a yellowish-brown tint. This will significantly impair your vision at this final stage, and night vision and color sharpness will also reduce drastically.

Brunescent cataracts

This type of cataract represents the advanced form of the nuclear cataract. When a nuclear cataract goes untreated for a while, the lens becomes hardened as it forms a brownish or yellow tint known as a brunescent, and this impairs vision further.

Secondary cataracts

Most often, secondary cataracts are caused by cataract surgery. Officially known as posterior capsular opacification, these form when a few cells are left behind during cataract surgery, and those cells begin to change.

The use of steroids has also been linked to the development of secondary cataracts.

Zonular/lamellar cataracts

This type of cataract is caused by a genetic mutation in the HSF4 gene.

Initially, it features tiny, white marks in the eye’s nuclear layer. Without early treatment, it will spread all around the eye lenses, causing severe visual impairment or even blindness in some cases.

Cortical cataracts

This kind of cataract is similar to nuclear cataracts; however, a cortical cataract begins in the cortex of the eye. It appears as white wedge-like formations directed toward the eye’s center.

This cataract makes night vision extremely difficult because it scatters incoming light. Reading or driving at night becomes more challenging and dangerous in this condition.

Cortical cataracts are usually related to aging. Other factors include smoking, diabetes, poor diet, high blood pressure, and exposure to UV radiation.

Anterior subcapsular cataracts

This type forms at the center of the eye, preceding the lens capsule. It mainly results from a physical impact on the eye or an infection that causes significant inflammation or swelling. Atopic Dermatitis is also another cause of anterior subcapsular cataracts. It is a skin condition that can affect the eye and features sudden appearance of red, itchy bumps on the affected area.

Posterior subcapsular cataracts

In this case, the cataract develops behind the lens capsule.

The cause of this type of cataract is mainly attributed to genetics.

Correcting this cataract in the advanced stages involves a more complex procedure than with the anterior subcapsular cataract.

Anterior polar cataracts

This cataract, most often seen in children, has the most negligible effect on vision as it doesn’t affect the transmission of incoming light. It appears as a white dotted film at the center of the eye directly in front of the lens.

This type of cataract is congenital, meaning that children are born with them.

Posterior polar cataracts

This type of cataract is similar to anterior polar cataracts and forms right behind the eye nuclear layer. It also has little to no effect on vision, and its origin is associated with genetics.

Congenital cataracts

This type mainly affects infants and younger children. If these cataracts develop central to the eye nucleus, they will require correction. But if they are scarce and peripheral to the lens, surgery may not be necessary.

Congenital cataracts can have a genetic origin, or they may be caused by injury during pregnancy or labor. Uncontrolled blood sugar levels and infections during pregnancy raise the risk for congenital cataracts.

Traumatic cataracts

This cataracts class is caused mainly by blunt force impact to the eye or any external physical stimuli directed toward the eye, such as contact with corrosive compounds or extreme heat.

In this case, you may observe signs of the cataract immediately after impact or much later, as the eye heals. The extent of physical damage will determine the possibility of correction.

Radiation cataracts

This type of cataract is caused by radiation, such as that used in cancer treatment. The benefits of radiation treatment are viewed as outweighing the increased risk for cataracts.

The sun’s UV rays can also contribute to cataract formation.

Post-vitrectomy cataracts

Vitrectomy is a vision-correction procedure applied to correct various eyesight issues. The surgical procedure may be successful in some respects but has also been known to cause cataracts in some patients.

Polychromatic cataracts

This cataract develops in later adult ages and is also referred to as the Christmas tree cataract, owing to its appearance as brilliant, multi-colored, crystal-like formations on the eye’s lens.

This type of cataract mainly affects people who have a common variant of muscular dystrophy, known as myotonic dystrophy.

Diabetic snowflake cataracts

In this variant, the area surrounding the lens first develops tiny white and gray patterns that resemble snowflakes. As the name suggests, this type of cataract develops in people who have diabetes. 

Other known causes of cataracts include the following:

• Smoking 
• Excessive production of oxidants in the body
• Long-term exposure to some medications and steroid supplements

How Do Cataracts Form?

Cataracts form when the lens of the eye becomes cloudy. Most often, this occurs due to normal changes in the eye that happen with age.

As we get older, the protein membranes in the lens begin to deteriorate and bunch together on the eye’s lens. Over time, as the cluster becomes bigger, they begin to obscure vision, causing murkiness.

Since the lens of the eye works to focus light, a cataract can thwart this process, resulting in blurry vision. Once the cataract is removed, the lens is once again able to focus light correctly.

Risk Factors for Cataracts

Cataracts are incredibly common with age. In fact, over 90 percent of people over age 65 will have a cataract. 

While most cataracts are related to age, some situations, elements, and stimuli can trigger early or extreme development of cataracts. Risk factors for cataracts include the following:

• Genetic history of cataracts 
• Excessive and prolonged smoking 
• Excessive and chronic alcohol consumption
• Indulging in a highly oxidative diet
• Pre-existing conditions, such as diabetes, obesity, and high blood pressure
• Regular exposure to sunlight, x-rays, or other radiation without protective gear
• Physical impact that causes significant eye injury
• The natural process of aging

How to Potentially Reduce Risk of Developing Cataracts

To potentially minimize the possibility of developing cataracts, practice the following steps:

• Limit your alcohol intake. 
• Quit smoking.
• Increase intake of antioxidant foods, such as those that are high in vitamin C, B vitamins, and omega-3 fatty acids. 
• Engage in physical fitness and weight management tactics to reduce risk of obesity and high blood pressure.
• Always wear protective eye gear to guard the eyes from injury from objects and other irritants, and to filter out any UV radiation.

References

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4. PRELEX Surgery Reduces Need for Spectacles, Surgeons Say. (February 2002). Ocular Surgery News.

5. Eyelid Surgery: Blepharoplasty. American Society of Plastic Surgeons.

6. Diabetic Retinopathy. (January 2021). American Optometric Association (AOA).

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8. LASIK. (March 2018). United States Food and Drug Administration (FDA).

9. New Research Sheds Light on How UV Rays May Contribute to Cataract. (June 2014). National Eye Institute.

10. Nutritional Modulation of Cataract. (November 2013). Nutrition Reviews.

11. Emerging Trends and Research Foci in Cataract Genes: A Bibliometric and Visualized Study. (August 2021). Frontiers in Genetics.

12. The Pathophysiology of Cataract and Major Interventions to Retarding Its Progression: A Mini Review. (February 2017). Advances in Ophthalmology & Visual System.