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Related Concept Videos

Vision01:24

Vision

Vision is the result of light being detected and transduced into neural signals by the retina of the eye. This information is then further analyzed and interpreted by the brain. First, light enters the front of the eye and is focused by the cornea and lens onto the retina—a thin sheet of neural tissue lining the back of the eye. Because of refraction through the convex lens of the eye, images are projected onto the retina upside-down and reversed.
Photoreceptors and Visual Pathways01:22

Photoreceptors and Visual Pathways

At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...
Sight Distance in a Vertical Curve01:29

Sight Distance in a Vertical Curve

Sight distance on vertical curves is critical in roadway design. It ensures drivers can see far enough ahead to identify and respond to hazards effectively. This directly impacts safety, driver comfort, and the overall efficiency of the transportation network.Vertical curves are classified into crest and sag curves based on their geometry. For crest curves, sight distance is determined by the line of sight between a driver's eye and a small object on the road's surface. Design parameters for...
Glaucoma: Overview01:25

Glaucoma: Overview

Glaucoma is an eye condition characterized by increased intraocular pressure that damages the retina and optic nerve, leading to irreversible blindness if left untreated. The human eye has various components, including the cornea, iris, pupil, lens, and optic nerve. Aqueous humor is secreted by the epithelium of the ciliary body in the posterior chamber and flows through the trabecular meshwork and canal of Schlemm, maintaining normal intraocular pressure. The trabecular meshwork and the canal...
Angle Closure Glaucoma: Treatment01:28

Angle Closure Glaucoma: Treatment

Angle-closure glaucoma, or closed-angle glaucoma, is an eye condition where the iris bulges out and blocks the iridocorneal angle, resulting in a buildup of aqueous humor and increased intraocular pressure. Immediate medical attention is necessary due to the sudden onset of symptoms. The treatment for angle-closure glaucoma includes short-term and long-term approaches. Short-term treatment involves using eye drops like pilocarpine to lower intraocular pressure by increasing aqueous humor...
Color Vision01:24

Color Vision

Color perception begins in the retina, the light-sensitive layer at the back of the eye. Two main theories explain how colors are seen: the trichromatic theory and the opponent-process theory. The trichromatic theory, proposed by Thomas Young in 1802 and extended by Hermann von Helmholtz in 1852, suggests that color vision is based on three types of cone receptors in the retina. These cones are sensitive to different but overlapping ranges of wavelengths corresponding to red, blue, and green.

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Related Experiment Video

Updated: Jul 2, 2026

Subjective Refraction Test Using a Smartphone for Vision Screening
05:36

Subjective Refraction Test Using a Smartphone for Vision Screening

Published on: October 18, 2024

Vision 2020 - the right to sight.

S Resnikoff1, I Kocur, D E Etya'ale

  • 1Prevention of Blindness and Deafness, Chronic Diseases Prevention and Management, World Health Organization, 20 Avenue Appia, CH-1211 Geneva 27, Switzerland.

Annals of Tropical Medicine and Parasitology
|September 26, 2008
PubMed
Summary
This summary is machine-generated.

The global Vision 2020 initiative, launched in 1999, aims to eliminate avoidable blindness. It has expanded partnerships and reduced blindness from onchocerciasis and trachoma, though cataracts remain a leading cause.

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Last Updated: Jul 2, 2026

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Area of Science:

  • Public Health
  • Ophthalmology
  • Global Health Initiatives

Background:

  • The success of Mectizan donation for onchocerciasis control inspired a broader initiative.
  • Avoidable blindness remains a significant global health challenge.

Purpose of the Study:

  • To outline the establishment and objectives of the Vision 2020 initiative.
  • To report on the progress and achievements of Vision 2020 since its inception.

Main Methods:

  • The initiative is co-ordinated by the World Health Organization and the International Agency for the Prevention of Blindness.
  • It focuses on three pillars: disease control, human resource development, and infrastructure development.

Main Results:

  • Partnership has grown to over 60 member organizations.
  • Prevention activities have been revitalized.
  • Vision 2020 plans are complete in 40% of countries.
  • Significant reductions in blindness due to onchocerciasis and trachoma have been observed.

Conclusions:

  • Vision 2020 has demonstrated progress in controlling specific causes of blindness.
  • Cataract remains the primary cause of avoidable blindness, requiring continued focus.