Model demonstrating different types of eye sight, Europe, 1880-1900
Showing how light enters the eye in long sight, normal sight and short sight; this is a 3-D model of the light diagrams seen in many science and medical textbooks. The model was probably used as a teaching aid for students studying the eye. In normal sight, the light rays meet up at the retina, the sensitive part of the eye, and send a message to the brain through the optical nerve. Long sight (not being able to see close up) means that the light meets behind the retina; short sight (not being able to see far away) occurs when light meets up in front of the retina. Both conditions can be corrected with glasses. For a person with both long and short sight, bi-focal lenses can be used.
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The branch of medicine dealing with the diseases and surgery of the visual pathways (usually the eyes or the brain).
Glossary: model - representation
Use for a scaled representation of an object or structure, usually three-dimensional. The item is often idealised or modified to make it conceptually easier to understand.
A defect of the eye where images are produced in front of the retina rather than on it. This causes object that are close to the viewer to appear blurred. Usually treated with glasses or corrective surgery.
A defect of the eye where images are produced behind the retina rather than on it. This causes objects that are further away from the viewer to appear blurred. Long-sightedness is usually treated with glasses or corrective surgery.
A spectacle lens that is used for both long and short sight.