Many years ago, 11 to be exact, I worked with a Coburn 108, I think it was, in an optical lab owned by an optometrist in Austin. We blocked with alloy. It was a small lab and I think Alley Oop trained me. Computers sent rockets to the moon, etc.
I quit and went to do other things.
Fast forward to the 21st century, and I have gone back into an optical lab and am re-learning pretty much from scratch. We block with wax, and a computer spits out the lab sheet and tells the SGX what to generate for the Rx.
When I worked in the cave in the 1990's we had a small blocking ring with a cutout for the seg on the inside of the ring for lined BF's. We decentered manually and turned the inset and the seg ABOVE the 180 line of the block to prevent the alloy from running off through the cutout.
In my present lab, it doesn't matter, as far as run-off of the wax is concerned, as the ring is big enough to include the seg, but I have been told that I must put the seg BELOW the 180 line of the block as much as possible as putting it ABOVE the 180 will cause prism.
I am told that this is because the computer program has been written to assume that the seg is BELOW the 180, or on the bottom side of the block.
I realize that a computer program can incorporate a lot of variables that I cannot consider and can use them to generate a lens, but will turning the seg one way or the other cause prism if the cylinder axis is blocked properly?
Help?
I can't think without my coffee!!!!
Thanks,
Don
Bookmarks