[tig] eye charts

Rob Lingelbach rob
Mon Nov 22 22:33:53 GMT 2004


waiting in the doctor's office the other day, I had the opportunity to
study the eye chart, in this case the Snellen Type plastic eye chart
also known as a Graham Field Chart.

I notice that certain letters are represented more than others, and
certain ones are left off completely.  You get the top "E" then "F P"
then "T O Z" then "L P E D", then 7 more lines, increasing on the 11th
line to 11 letters, which makes a total of 66 letters.  The letters
not represented are  A,B,G,H,I,J,K,M,N,Q,S,U,V,W,X,Y.  I wonder why
CDEFLOPRTZ are the only ones used?

--Rob

Rob Lingelbach  
tig founder, coadmin
http://www.colorist.org/robhome.html
Key fingerprint = E547 6FD3 13D2 A1AB F795  B102 80D6 4C93 F73A 7736
Public key avaialable on pgp.mit.edu





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