Cataracts in humans happen when the clear lens inside the eye becomes cloudy, mostly due to age-related changes in the lens proteins, but several other medical and lifestyle factors speed this up.

What is a cataract?

  • A cataract is a cloudy area that forms in the eye’s natural lens, which normally focuses light so you can see clearly.
  • As the lens proteins and fibers break down or clump together, vision becomes blurry, hazy, or less colorful.

Main causes inside the eye

  • Aging (most common cause) – With age, the lens tissue changes and its proteins gradually clump, leading to clouding; most cataracts are age‑related.
  • Genetics / family history – Having close relatives with cataracts increases your chances, suggesting inherited susceptibility of the lens.
  • Other eye problems or procedures – Previous eye surgery (for example, glaucoma surgery), long‑standing inflammation inside the eye (uveitis), or severe nearsightedness can trigger cataract formation.
  • Eye injuries (traumatic cataracts) – A hard blow, cut, puncture, chemical burn, or intense heat can directly damage the lens and cause it to turn cloudy, sometimes years later.

Whole‑body health factors

  • Diabetes and other systemic diseases – High blood sugar and some metabolic disorders change the lens environment and make cataracts more likely and often earlier in life.
  • Long‑term steroid use – Prolonged use of corticosteroid medicines (by mouth, as eye drops, or inhaled) is a well‑known cause and risk factor.
  • Radiation and cancer treatment – Radiation therapy to the head/neck or exposure to certain types of radiation can damage lens cells and lead to cataracts.

Lifestyle and environmental triggers

  • UV light from the sun – Regular, unprotected exposure to ultraviolet rays speeds up lens aging and cataract formation.
  • Smoking – Smoking increases oxidative stress in the lens and is repeatedly linked with faster cataract development.
  • Excess alcohol – Heavy, long‑term alcohol use is associated with a higher risk of cataracts.
  • Obesity – Being obese appears in risk‑factor lists, likely through effects on metabolism and related diseases like diabetes.

Special types and timing

  • Age‑related cataracts – Make up around the vast majority of cataracts and usually appear after about age 40, becoming more common in people over 60.
  • Congenital (present at birth) – Can result from infections or inflammation during pregnancy (for example, rubella), or inherited genetic changes affecting lens development.
  • Secondary cataracts – Occur after other eye diseases, surgery, long‑term steroid use, or systemic conditions like diabetes.

Quick prevention snapshot

While you cannot fully “prevent” cataracts, you can lower risk or slow them by:

  • Protecting eyes from UV (sunglasses, hats).
  • Not smoking and limiting alcohol.
  • Managing diabetes and other chronic conditions well.
  • Avoiding unnecessary long‑term steroid use and getting regular eye exams as you age.

TL;DR: Cataracts are mainly caused by aging changes in the eye’s lens, but diabetes, genetics, eye injuries or surgery, long‑term steroids, UV exposure, smoking, and heavy alcohol use all contribute to how early and how fast they develop.

Information gathered from public forums or data available on the internet and portrayed here.