While the most common cause of cataracts is “having birthdays”, our nice way of saying, “getting older”, there are many causes of cataracts. The human lens forms prior to birth with thousands of small clear proteins packing themselves tightly into a thin shell. The size of the natural lens is approximately 3-4mm thick and about the size of a common household lentil. When the natural lens becomes cloudy it is then called a cataract. There are many types of cataracts, each one developing for a different reason. In this article, we’ll review some of the most common causes of cataracts.

What Causes Cataracts?

When the natural lens inside our eye becomes cloudy, it’s called a cataract. The natural lens in nearly all of us starts out clear and flexible. As we age, it becomes cloudy. Most of us are aware of cataracts being the result of getting older. However, what many don’t realize is that there are many different causes of cataracts. Read on to learn about the many different causes.

Symptoms of Cataracts

Cataracts grow slowly over time and patients sometimes do not notice their effects until they begin impacting their activities. Common symptoms of cataracts include cloudy vision, halos around lights, dark or dim vision, and poor night vision. Frequent changes in glasses occur as well as increased near vision.

There Are Many Different Causes of Cataracts

Let’s review the causes of cataracts. There are common causes, and there are also quite rare causes. In the following sections we’ll go over the major different things that can cause cataracts

Aging Is The Most Common Cause Of Cataracts

By far the most common reason for cataract development is due to advancing age. This occurs because the proteins within the lens continue to divide and grow throughout life within a confined space. After decades of growth, the lens begins to thicken, a process called nuclear sclerosis. These lens proteins also discolor leading to changes in the way light and color are filtered and viewed. Although not completely understood, there are some factors of daily life that can speed up the development of cataracts. These factors include spending time in bright sunlight without sunglasses, smoking, and an unhealthy diet.
Cataract Close-Up

Medications Can Cause Cataracts

The most common medication that causes cataracts are oral, intravenous, and inhaled steroids. This type of cataract typically forms within 5-10 years of medication use and is most commonly termed a posterior subcapsular cataract. Although these cataracts can be quite visually disturbing, they are straightforward to remove, and visual recovery is quick.

The type of steroids that cause these cataracts are called “corticosteroids”. They are different from anabolic steroids that are used for athletic performance.

There are other kinds of medications that can cause cataracts or have been linked to them. Let’s review a few medications that have been associated with cataracts:

  • Phenothiazines: Causes deposits on the anterior lens capsule which are generally visually insignificant
  • Miotics: There is a correlation of cataracts with eye drops such as pilocarpine after years of use
  • Amiodarone: Can cause stellate pigment deposits. Only rarely are visually significant
  • Statins: Studies in dogs have shown association with cataracts, however, this has not been observed in humans.

Posterior Subcapsular Cataract from steroids

Trauma Can Cause Early Cataracts

Blunt forces to the eye or surrounding face can cause a special type of traumatic cataract called a “stellate cataract”. As the proteins within the natural lens undergo extreme pressure and movement they begin to cloud and swell. Over time the lens becomes pressurized and requires special considerations during surgery as well as a higher risk of complications.

Penetrating trauma can also result in early cataracts. If something sharp enters the eye and touches, or tears, the capsule which supports the natural lens, a cataract will develop. These types of cataracts when the support structure has been damaged can often be some of the most challenging and complex cases.
Stellate Star-Shaped Cataract from trauma
Other types of injuries to the eye can also result in early cataracts. These include chemical injuries, radiation exposure, intraocular foreign bodies, and electrical injuries.

Prior Intraocular Surgery Can Cause Cataracts

Procedures inside the eye such as retinal surgery, specifically vitrectomy, can disturb the delicate lens and cause it to cloud.

When patients require vitrectomy for conditions like epiretinal membranes or retinal detachments it is quite common for a cataract to develop within the first 12 months after surgery.

Diabetes Is A Common Cause of Cataracts

The list of medical conditions that can cause a cataract is extensive, but the most common medical condition that causes cataracts is diabetes. As the bloodstream takes on more glucose, the lens begins to change its energy demands. This leads to swelling within the lens and changes to its shape and size, leading to cataract development. This type of cataract is termed a “snowflake” cataract.

Diabetes is a common cause of cataracts, particularly in patients with poorly controlled diabetes. When diabetes is poorly controlled, and blood glucose is very high, the onset of cataract is accelerated. The best thing patients can do to prevent the early onset of cataracts from diabetes is to control their blood sugar well.

Metabolic Disorders Can Result in Early Cataracts

There are a variety of metabolic disorders that can result in early cataracts. Metabolism refers to the processes the body uses to break down different molecules inside the body. When there are metabolic disorders, certain molecules cannot be broken down and they can build-up resulting in disorders.

For example, in the condition called “galactosemia”, the body is unable to convert galactose to glucose. As a result, galactose accumulates in the body causing a variety of problems, including cataract.
Metabolic Disorders that cause cataracts-Galactosemia-Hypocalcemia-Myotonic Dystrophy-Wilson Disease

Congenital Cataracts

In rare circumstances an infant can be born with cataracts, these are called congenital cataracts. Any child with cataracts needs a full comprehensive exam with a pediatric ophthalmologist to rule out dangerous metabolic diseases, retinal problems, and rare malignancies.

Although congenital cataracts are rare, there are many possible causes. See the list below.
Causes of Congenital Cataracts List, first item, Genetic Disorder, sublist, Down syndrome, Lowe Syndrome, Hallermann-Streiff Syndrome, Marfan Syndrome, Alport Syndrome, Myotonic Dystrophy, Fabry Disease, Conradi Syndrome, second item, Maternal Infection, sublist, Rubella, Cytomegalovirus, Varicella, Syphillis, Toxoplasmosis, third item, Congenital Ocular Abnormalities, sublist, Persistent Fetal Vasculaturs, Tumors, Aniridia, Anterior Segment Dysgenesis

Does smoking cause cataracts?

Yes. According to the FDA’s website, smoking cigarettes can, in fact, cause cataracts. The United States Department of Health and Human Services published a report in 2004 titled “The Health Consequences of Smoking” which the FDA cites as their reference.

How Are Cataracts Treated?

Regardless of the cause of cataracts, they are all treated basically the same, with surgery. Typically, cataract surgery in children is performed by pediatric ophthalmologists, while cataracts in adults are performed by adult ophthalmologists. Children have special considerations, often related to anesthesia, that require a pediatric specialist, often with a team of pediatric anesthesia providers.

In general, the cataract is surgically removed, and a lens implant is put in its place.


Although there are many ways that cataracts can develop, the surgical treatment of cataracts is straightforward with a high success rate. Patients can look forward to better vision and decreased reliance on their glasses and contacts with an experienced surgeon offering the latest options for cataract surgery with intraocular lens replacement.