1. Your Sight
  2. Cataract
Close up of woman's eye


The following medical information does not constitute professional medical advice. If you have any specific questions about any medical matter, you should consult your doctor or professional healthcare providers.


Cataract occurs when the lens, in one or both eyes, become cloudy. 

The lens is the coloured part of your eye and is normally clear to help focus the light entering the eye to form an image. Cataract develops due to changes in the arrangement of the cells in your lens and its water content, which causes the lens to become misty. When this happens, light cannot pass directly through the lens, leading to a progressive deterioration of your vision with time.   

Ageing is the most common cause of cataract, affecting approximately half of those aged over 65 years and 70% of those aged over 85 in the UK.1,2 It is estimated that around 22 million adults aged 40 or older have some form of cataract, and given a global projection for an ageing population, this number is predicted to double by 2020.2

You are also more likely to develop cataract if you have long-term diabetes, prior eye injury or surgery, use corticosteroid medication or receive radiation treatment.3,4

Age-related cataract or cataract caused by diabetes or medication is most likely to affect both eyes, whereas an eye injury is more likely to affect only one eye.3 Cataract can also occur in childhood, but in some cases it is a symptom of another illness.4

Cataract normally progresses slowly with time. If you have a cataract, you may notice blurry vision, extra sensitivity to light, double vision, bright colours appearing faded and trouble seeing at night.1,3

Your eye healthcare professional is able to detect cataract, even during early stages of development when you might not notice any initial changes to your sight, and so it is important to take regular eye tests.3 

While cataract is the world’s leading cause of blindness, affecting 65 million people worldwide,4,5 it can be treated with surgery. 
The surgical procedure involves the cloudy lens being replaced with an artificial lens, also known as an intraocular lens (IOL). Surgery is the only treatment method available and can be performed at any stage of cataract development. Following treatment, the IOL will not need to be changed in the future.3  



  1. American Academy of Ophthalmology. What are cataracts? Available at: Last accessed December 2019
  2. News Cataract epidemiology. Available at: Last accessed December 2019
  3. The Royal College of Ophthalmologists. Understanding cataracts.
  4. Harvard Health Publishing. Cataract: symptoms, diagnosis, and treatment. Available at: Last accessed December 2019
  5. World Health Organisation. World report on vision