XPost: uk.d-i-y   
   From: jj9801@nospam.com   
      
   "Tim Watts"  wrote in message   
   news:0mmi0c-j0m.ln1@squidward.dionic.net...   
   > On 21/04/15 19:51, Cursitor Doom wrote:   
   >> On Tue, 21 Apr 2015 19:37:31 +0100, Tim Watts wrote:   
   >>   
   >>> On the subject of glasses, for a single focus lens for a short sighted   
   >>> person, how are intermediate lenses sepcified (ones you might use for   
   >>> reading plus computer work at up to say 1m)?   
   >>>   
   >>> Is the far sight dioptre power changed (by a factor or actually   
   >>> prescribed by the optician) or is the far sight dioptre given to the   
   >>> lens maker along with a request for "intermediate"?   
   >>   
   >> People have varying requirements when it comes to intermediates, so you   
   >> can't just specify according to some preset formula. It requires a   
   >> separate sight test at the specific distance - one meter in your case; it   
   >> was 24" in mine. Assuming you're short sighted, the prescription will be   
   >> less negative. So for example if your distance script is -3.25 for each   
   >> eye your intermediate script will be -2.75 or thereabouts give or take a   
   >> bit. But you need to test at the appropriate distance to ascertain what   
   >> the 'give or take bit' is.   
   >>   
   >   
   > So in principle, if you have your far prescription, it ought to be   
   > possible to calculate an intermediate based on "I want to focus upto 1m   
   > instead of infinity"?   
      
   Yes, and there is a newsgroup that covers that stuff, I've added it.   
      
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