Neat paper .. thanks for sharing.
Type: Posts; User: Trip; Keyword(s):
Neat paper .. thanks for sharing.
With the vertical prism being apart of the near requirement I would look to a Franklin vs decentration, can still keep as a D segment to help manage thickness.
Decentering the segs for near horizontal prism is not uncommon. We generally only consider the add power for calculating the amount of decentration needed, and in this case if we are asking for 2...
andshewas
I've done more thinking/reading and found a (pretty old) article suggesting different corridor lengths for each lens:
http://www.sciencedirect.com/science...39625798000393
The theory...
I would also check to see if there has been any change in cylinder axis and power moving from or to a more oblique meridian.
Has anyone experienced any challenges with prescribed prism and full backside designs? This is a generic question vs a specific pt. issue.
thanks,
Curious, isn't there merit in pointing out a life time of exposure in this discussion? .... life expectancy has exceeded what evolution originally provided/designed for ... ... what does an extra...
Then split the difference for the modified B and adjust your hgt by 4.5mm.
My understanding suggests that a long vertex distance is better served by a corresponding longer progressive corridor. The logic that the eye is exposed to more of the lens surface, thus indicating...
Can't visualize doing any lens work with the contraption. Edging, grinding, ... nada ....., curious if someone recognizes what function it did perform.
One better uh ….. , “chuckle” ….. appears to be a tad more than that.
Played with the last file a bit … thanks for sharing, … for me a wonderful illustration of the prism differences between the...
Yes, one of the things that I had also considered with the difference in corridor length. Considering a generic 3mm difference in where the full add power takes effect I thought there may be a modest...
During the last few months I have had two antimetropic Rx’s that were originally unsuccessfully fitted with progressive lenses. The complaints were both centered on discomfort at near. One had been...
The lens blanks for flat tops will have fixed drop and decentration for the segment, and a change in seg height will mean a change in minimum diameter for cut out ... which will impact lens thickness.
Yah .. certainly exposed to power errors. I would always recommend grinding Rx prism when using an aspheric lens, ...... however you can probable get away with inducing the prism through...
Well unless you are grinding in excess of 20d of prism at that power, I'm gonna have to disagree.
Still trying to rationalize the value of the yoked prism in relation with this Rx. The deflection for upward gaze is very modest and would seem to be completely eroded by any off axis viewing ........
Yah .. 1 BD ou seems lite relative to power.
My first thought is that there is a difference in the monocular PD's between the clear / suns ..... and or the lens(es) are bit tilted/twisted from edging or mounting.
Second .. is there any...
Crystalline lens vs cornea, .... yah?
Normally the OC will default to the geometric center if not otherwise specified / dependent upon minimum height defined in the LMS for that seg style / material.
If verifying Rx prism, then start...
http://precisiontooltech.com/store/products/category/surfacing-department/
you can try here ....
Ah .. simple enough. I was trying to figure out if for some reason due to the shorter axial length or magnification of the lens power was leading to more challenges for the hyperope in FBS. .......
[As Optical24/7 pointed out, high plus/high add PALs perform better when the progressive optics are on the front.
When someone has a moment, would appreciate an explanation on why high plus/...
Chris wouldn't you want to protect the retina as much as possible? Obviously not restoring night vision or other visual enhancements but protective of an at risk region.