Relief for Human Suffering Foundation

Refractive Errors

What Are Refractive Errors?

Refractive errors are caused by irregularity in the shape of the eyes, which keeps incoming light from focusing correctly on the retina located in the back of the eye, making it hard to see clearly2. Refractive errors are the most common type of visual impairment and can be treated with eyeglasses, contacts, or surgeries2. 

Types of Refractory Refractive Errors:

The National Eye Institute lists four common types of refractive errors:

  • Nearsightedness or myopia: cannot clearly see things that are far away
  • Farsightedness or hyperopia: cannot clearly see things that are close-up
  • Astigmatism: objects that are close up and far away look warped or blurry
  • Presbyopia: middle-aged and older people have a hard time seeing up close

What are causes or Risks of Refractive Errors?

Genetics, family history, and aging can be causes and risks for developing refractive error forms of visual impairment. 

What are the Symptoms of Refractory Errors?

Blurry vision is the most common symptom.

Other symptoms include:

  • Double vision
  • Blurry/hazy vision
  • Noticing halo or glare when looking at lights
  • Squinting to try to focus
  • Headaches
  • Eyes feel sore or tired
  • Trouble focusing when reading 
  • Issues can be present with corrective lenses that need to be updated


Percentage of all visual impairments caused by refractive error.


Percentage of visual impairments that are easily treated with glasses or cataract surgery.

1.1 Billion

Number of people with uncorrected refractory error impairments.


  1. National Eye Institute. (2022). Refractive Errors. Retrieved from
  2. World Health Organization. (2019). World report on vision.
  3. Burton, M. J., Ramke, J., Marques, A. P., Bourne, R. R. A., Congdon, N., Jones, I., Ah Tong, B. A. M., Arunga, S., Bachani, D., Bascaran, C., Bastawrous, A., Blanchet, K., Braithwaite, T., Buchan, J. C., Cairns, J., Cama, A., Chagunda, M., Chuluunkhuu, C., Cooper, A., … Faal, H. B. (2021). The Lancet Global Health Commission on Global Eye Health: Vision beyond 2020. The Lancet Global Health Commission, 9(4), e489–e551. doi:10.1016/S2214-109X(20)30488-5