A +4.50D lens needs to be decentred 4mm inwards to line up with the pupil. If prism is ordered 3 base in, what would be the total decentration of the lens?
Can someone help? :)
Whitney
A +4.50D lens needs to be decentred 4mm inwards to line up with the pupil. If prism is ordered 3 base in, what would be the total decentration of the lens?
Can someone help? :)
Whitney
Zero if it lines up with the pupil in distant gaze.
As ususal Chip didn't read the entire post before shooting out an answer. Once again, my appologies.
Last edited by chip anderson; 07-01-2008 at 07:41 AM. Reason: Admitting stupidity
Since prism = c * F
c = prism/F = 3/4.50 = 0.67cm = 6.7mm
A plus lens decentered inwards creates base in prism. Therefore the lens would have to be decentered in an additional 6.7mm or 10.7mm total (4mm + 6.7mm) to create the 3 prism dioptres BI.
woohoo i was right :D
Thanks guys!
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