Least distance of distinct vision
![](http://upload.wikimedia.org/wikipedia/commons/8/8f/Focal-length.png)
In optometry, the least distance of distinct vision (LDDV) or the reference seeing distance (RSD) is the closest someone with "normal" vision (20/20 vision) can comfortably look at something.[1] In other words, LDDV is the minimum comfortable distance between the naked human eye and a visible object.
The magnifying power (M) of a lens with focal length (f in millimeters) when viewed by the naked human eye can be calculated as:
See also
- Optometry
- Far point
- Snellen chart
- Visual perception
- Visual impairment
References
- ^ Katz, Milton (August 1996). "Convergence Demands by Spectacle Magnifiers". Optometry and Vision Science. 73 (8): 540–545. doi:10.1097/00006324-199608000-00004. ISSN 1538-9235. PMID 8869985. S2CID 21041392.
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