EYESIGHT – GENERAL INFORMATION
Friday, May 15, 2009 | 2:55 am
Distance vision is normally tested from six metres.
The Americans test vision at 20 feet, and use this number rather than metres.
Thus normal vision for Americans is 20-20, while for us it is 6-6.
So a person who can see only the top letter at this distance has 6-60 of normal vision.
Similarly, the second line of letters should be seen by a person with normal sight from 36 metres.
If you can read no further than this, then your vision is 6-36.
Similarly, with the other lines which are equivalent to 6-24, 6-18, 6-12, 6-9 and 6-6 is normal vision.
Near-vision is tested by means of the Jaeger types, which simply consist of the ordinary printers’ types from the smallest upwards.
In hypermetropia or long-sightedness, the person complains of difficulty with near-vision, while his distance vision is good.
In the eye, the ciliary muscles constrict the lens and enable it to focus the light. However, the constant strain of doing this may cause headaches.
(posted in General health)
Find this post interesting? Besides commenting below, you can follow responses with the RSS 2.0 feed or
trackback from your own site.
Leave a Comment
You must be logged in to post a comment.
Starburst Theme designed by Claire
powered by WordPress 2.7Entries (RSS) and