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What Causes Cataracts

What Causes Cataracts

Cataracts are most commonly associated with ageing, but they do not develop in the same way for everyone. While the underlying change within the lens is well understood, a range of factors can influence when cataracts develop, how quickly they progress, and how significantly they affect vision

Age as the primary factor

What causes cataracts? The most common cause of cataracts is natural ageing of the lens. Over time, gradual changes occur within the lens that affect its clarity. These changes are part of the normal ageing process and will occur to some degree in most people. However, the rate and impact of these changes vary, which is why cataracts may develop earlier or become more noticeable in some individuals.

Systemic health factors

Certain health conditions can influence the development or progression of cataracts.

These do not necessarily cause cataracts directly, but they can accelerate the underlying changes within the lens.

Examples include:

  • Diabetes
  • Chronic systemic conditions affecting metabolism

In these situations, cataracts may:

  • Develop at a younger age
  • Progress more quickly
  • Have a greater impact on vision earlier

Long-term use of certain medications can contribute to cataract formation.

Most notably:

  • Corticosteroids

These medications can alter the internal environment of the lens over time, increasing the likelihood of lens clouding.

Trauma and local eye factors

Cataracts may also develop as a result of direct changes within the eye, including:

  • Previous eye injury
  • Inflammation within the eye
  • Prior eye surgery

In these cases:

  • Cataracts may develop more rapidly
  • One eye may be affected more than the other

Environmental and lifestyle contributions

External factors can influence the rate at which cataracts develop.

These include:

  • Long-term exposure to ultraviolet (UV) light
  • Smoking
  • General health and lifestyle patterns

These factors are thought to increase oxidative stress within the lens, contributing to earlier or more pronounced changes.

Genetic and individual variation

Some individuals are more likely to develop cataracts earlier due to genetic predisposition.

Less commonly:

  • Cataracts may be present at birth
  • Or develop during childhood

However, most cataracts remain age-related, with genetics influencing timing rather than inevitability.

Why timing differs between people

Not everyone develops cataracts at the same stage of life, and not all cataracts progress at the same rate.

This variation is influenced by a combination of:

  • Age
  • Health status
  • Environmental exposure
  • Genetic factors

As a result, two individuals of the same age may have very different visual experiences.

What this means for you

Understanding what causes cataracts helps explain why vision may change over time. However, the presence of risk factors alone does not determine when treatment is needed. Decisions are based on how vision is affected, not simply why cataracts have developed.