Download presentation
Presentation is loading. Please wait.
Published byArlene Morton Modified over 8 years ago
1
ISO and ANSI Power tolerances vs. “Real world practice”
2
ISO and ANSI Power tolerances vs. ”Real World Practice” What happens in the real world when determining “RX DP power” acceptability? Record prescribed RX: OD: +.25 = -3.25 x 103 Measure fabricated RX: Is sphere error >.13? Absolute difference is.12, therefore sphere power acceptable Is cyl error >.13? Absolute difference is.07 and axis is 103 as prescribed, cyl is acceptable. Therefore, the lens Passes for power inspection
3
ISO and ANSI Power tolerances vs. “Real world practice” Shown above is the ISO 8980-1 and proposed “mounted pair” tolerance scheme, also adopted in ANSI Z80.1 -1995 It was adopted by the ANSI Z80.1 -1995 (US) its first attempt to “harmonize” with ISO Standards ANSI Z80.1 -1999 dropped each meridian, but still held on to stronger meridian (keeping it almost as complicated) Now let’s review what Standards authors expect the lab to do:
4
How does one inspect to comply with the ISO (ANSI Z80.1-1995) Table 1? The lens fails ISO tolerances for a power that is not displayed on the Focimeter, but must be calculated. It is also a failure to ANSI Z80.1 because of strongest meridian error, but few labs ever apply this. It passes the common practice of tolerancing the sphere and cyl.
5
What would you do? … or do what is practical and ignore the complicated table entirely? Use this table ? Dick Whitney – Chair VCA LTC May 2007
Similar presentations
© 2024 SlidePlayer.com Inc.
All rights reserved.