I'm taking a day release course in Ophthalmic lenses and I'd appreciate some clarification with a few areas of SAG if anyone can.
I can calculate edge thickness of round and shaped lenses easily enough but I got a bit lost during the lecture when it came to astigmatic lenses.
I have a lens (n=1.5) -4.00/-2.00 x90 edged 50x40mm oval with an axial thickness of 2mm. I have to find the vertical and horizontal edge thickness.
I know my principal powers are -4.00 and -6.00 but that's where I blank out.