Overview

Blindness refers to a significant loss of vision that cannot be fully corrected with standard medical treatment, glasses or contact lenses. People described as blind may have no light perception at all or may retain limited sight such as light perception, blurred images, or indistinct shapes. Vision loss can be present from birth (congenital) or develop at any age because of disease, injury, or degeneration. For general information, see basic definitions.

Causes and prevention

Worldwide, causes of vision impairment vary by region and age. In many low-income settings, avoidable causes such as untreated infections, lack of eye surgery, and nutritional deficiencies have been important contributors; examples include vitamin A deficiency and infectious eye diseases. In older populations, age-related conditions such as cataract and glaucoma, diabetic eye disease, and macular degeneration are common contributors. Traumatic injury and accidents can cause sudden loss of vision. Public health measures — vaccination, improved nutrition, access to eye care, early screening and treatment — reduce many preventable causes. For further reading on nutrition and disease links, see nutrition resources and infection and eye health. Specific conditions often mentioned are cataracts and injury prevention.

Eye health professionals measure vision with tests of visual acuity and visual field. Many countries have legal criteria to determine eligibility for disability services and accommodations. Those criteria commonly combine measures of acuity and field restriction and are used to allocate benefits and certify eligibility for services. For technical definitions and measurement standards, consult sources on visual acuity assessment. Legal or administrative definitions also emphasize conditions not correctable by standard glasses (spectacles) or contact lenses (contact lens correction).

Blindness is distinct from other visual differences. For example, color vision deficiency (often called color blindness) affects color discrimination but not necessarily overall acuity; see color vision. Other distinctions include partial sight (low vision) versus total blindness; low vision refers to reduced vision that still allows some useful sight with or without aids.

Living with vision loss: tools and strategies

People who are blind use a broad range of adaptations that support independence, education and employment. These include tactile systems such as Braille, orientation and mobility training with guide dogs and canes, and assistive technologies like screen readers, voice-activated devices, and electronic magnification. Rehabilitation programs teach daily living skills, and many communities provide services to help with workplace access and schooling. Historical and educational resources on Braille and mobility are available via guide dog and mobility, Braille history and practical Braille resources.

History and notable figures

Blindness has shaped many influential lives and led to innovations in communication and accessibility. Louis Braille developed a tactile writing system in the 19th century that remains central to literacy for many people who are blind. Prominent public figures who were blind or had severe vision loss include musicians and advocates whose achievements raised awareness and expanded opportunities; see profiles of noted artists, musical pioneers, and advocates such as well-known historical figures. Their lives illustrate how social supports, education and technology contribute to participation in public life.

Practical notes and resources

  • Prevention: timely medical care, vaccinations, nutritional programs and safety measures reduce avoidable blindness.
  • Treatments: many causes are treatable or manageable—surgery for cataracts, medication for glaucoma, control of diabetes, and antibiotics for infectious eye disease.
  • Support: rehabilitation, adaptive technology and legal accommodations improve quality of life and access to work and education.

For more information about clinical details, services and support networks, consult local health authorities, ophthalmology centers and organizations specializing in vision rehabilitation.