Causes of Cataracts

Many things can cause a cataract to form, including diabetes, but it is believed that natural aging is the main culprit—at least for 99 percent of cataract sufferers (the other 1 percent are born with congenital cataracts, sometimes due to metabolic disorders or intrauterine infections).

For the majority of people with age-related cataracts,   cataracts : A clouding of the eye's lens that blocks passage of light to the retina, resulting in impaired vision. Often a result of normal aging, cataracts form when protein clumps cloud areas of the eye's lens. As the cataract progresses, vision worsens and often requires surgical replacement of the damaged lens with an artificial one.   or acquired cataracts, these develop very slowly and painlessly over the years and are often initially discovered by an eye doctor during routine exams, but may not be treated until your cataract impedes upon daily activities.

Types of Cataracts

To understand exactly how and why a cataract forms, you first need to know what kind of cataract it is. Following is a breakdown of the 3 most common.

Nuclear cataracts

Nuclear Cataract

The most common type, nuclear cataracts are associated with nearsightedness, blurry vision, and faded colors. As a nuclear cataract develops, the eye's lens   Lens: The transparent disc behind the pupil that brings light into focus on the retina.   becomes more curved and worsens nearsightedness, sometimes temporarily improving farsightedness but not for long.

Attributed as a consequence of natural aging, there are several reasons why nuclear cataracts form.

  • Just as skin sheds, so does the eye. But since cells can't be lost into the air inside the eye, they deposit into the lens, causing it to thicken and yellow.
  • Likewise, with aging, fewer nutrients reach the inner eye, contributing to the formation of an opaque nucleus.
  • Overexposure to ultraviolet light can also contribute, especially as the lens becomes harder, less resilient, and more opaque over time.
  • Several studies have also linked alcohol and exposure to cigarette smoke as cataract contributors.
  • Some systemic disorders, such as hypothyroidism (an underactive thyroid disease), diabetes, and in rare cases, glaucoma, can lead to cataracts as well.

Cortical cataracts

Cortical Cataract


Often associated with farsightedness and natural aging, cortical cataracts are less common and tend to develop in their own unique way.

  • They form when the shell, or cortex, of the lens becomes hard after developing post-birth and grows, usually till around age 60, when nearly 16 percent of the lens has become cortex.
  • Cortical production makes the lens more compact and hard, or sclerotic.   Sclerotic: Relating to sclerosis, the hardening of tissue.  

Posterior subcapsular cataracts

Posterior Cataract


Posterior subcapsular cataracts are even less common but affect vision more than any other type and tend to affect people under age 40 more often.

Since light converges at the back of the lens, extreme sensitivity to bright lights normally develops and reading can be extremely difficult.

Causes include:

  • Chronic intraocular inflammation due to overuse of medications such as corticosteroids.   Corticosteroids: A class of steroid hormones used to treat a variety of conditions. Chronic use may lead to the formation of posterior subcapsular cataracts.  
  • A penetrating injury to the lens, eye surgery, concussion, or the use of irradiation to treat an eye tumor, which can cause any type of cataract but typically result in posterior subcapsular cataracts.

Next: Cataract Prevention