A cataract is a clouding of the lens of the eye that reduces visual acuity and usually occurs bilaterally. With aging, the proteins of the crystalline lens begin to break down and precipitate, causing it to become opaque. They cause vision problems and are the most frequent cause of blindness, affecting more than 60% of people over 75 years of age.

The cause of the disease is the denaturation of lens proteins. The process may be favored by a number of risk factors:

  • Age. It is the main risk factor, being especially frequent in those over 70 years of age.
  • Other uncontrolled diseases, such as diabetes or hypertension.
  • Radiation. Excessive sun exposure (UV radiation), infrared rays or ionizing radiation can cause cataracts.
  • Eye injury or trauma.
  • Smoking.
  • Certain medications, such as corticosteroids.
  • Undiagnosed celiac disease.

Although the main risk factor for cataract development is aging, some genetic factors have been identified that may increase the risk of cataract development. In an association study carried out with some 670000 controls and more than 77000 affected individuals, 24 susceptibility loci were identified. These include the SLC24A3 gene, which codes for a transporter with an important function in retinal cells, transcription factors such as SOX2, or proteins with an important function in the retinal epithelium such as OCA2.


Cataracts develop slowly and painlessly, with a progressive worsening of vision. Once the cataract is already evident, visual problems may include:

  • Sensitivity to glare.
  • Cloudy, blurred, fuzzy or hazy vision.
  • Difficulty seeing at night or in dim light.
  • Double vision.
  • Loss of color intensity.
  • Trouble seeing outlines against a background or the difference between shades of colors.
  • Seeing halos around lights.
  • Most people with cataracts have similar changes in both eyes, although one eye may be worse than the other.


The appearance of cataracts is difficult to prevent because age is the main risk factor. However, there are a series of actions we can take to reduce the risk of cataracts appearing:

  • Avoid smoking.
  • Sun protection, with a hat and sunglasses when the sun directly hits the eye.
  • Avoid sun lamps and tanning booths.
  • Eat a healthy diet.
  • Control diabetes and/or hypertension in case of suffering from it.
  • Avoid the use of corticosteroids as much as possible.

Number of observed variants

13.5 million variants

Number of risk loci analyzed in the study

24 loci


Sakaue S, Kanai M, Tanigawa Y, et al. A cross-population atlas of genetic associations for 220 human phenotypes. Nature Genetics. 2021 Oct;53(10):1415-1424.

Mayo Clinic [March 2022]

American Academy of Ophthalmology [March 2022]

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