 | ||
 |  |  |
Detection of Astigmatism
To use any of the clipart images above (including the thumbnail image in the top left corner), just click and drag the picture to your desktop. You may also control-click (Mac) or right-click (Windows) and choose "Save file to disk" from the pop-up menu. Click here for help downloading and using clipart files.
* A TIFF file is a high-resolution (240 dpi) format. TIFF files should be used only if you are printing the clipart. Do NOT use TIFF files for clipart that will displayed on a computer screen. Click here for help downloading and using TIFF files. File Name: astigmatism_36776
Description: Lines for the detection of astigmatism. "The refracting surfaces of the eye acting together are equivalent in refracting power to a single, spherical surface of fairly short curvature. Frequently, however, the result is not the same as would be given by a perfect spherical surface, owing to inequalities in the curvature of the eye. In one direction the curvature may be greater than that at right angles to it. This tendency to a cylindrical form is called astigmatism. It interferes with the formation of perfect images and sometimes leads to serious eye strain in the effort to better the vision. Astigmatism may be detected by looking at black lines radiating from a point or at fine black concentric circles. Portions of the liens or circles appear gray and others black; the gray portions are out of focus. This defect is corrected by proper cylindrical glasses which equalize the curvature of the eye" — Newell, 1900
Source: Martin, H. Newell The Human Body: A Text-book of Anatomy, Physiology and Hygiene (New York: Henry Holt and Company, 1900) 272
Keywords: vision, retina, blindspot, "blind spot", "yellow spot"
Copyright: 2009, Florida Center for Instructional Technology. See license.
| Main Menu | Site Map | Search | License | Clipart Help |
Clipart ETC is a part of the Educational Technology Clearinghouse and is funded by various grants. Produced by the Florida Center for Instructional Technology, College of Education, University of South Florida. Email the project manager.