Progressive Lenes and the Lensometer

[William LDO]

Hopefully someone can educate me on this issue.
When I neutralize some progressive lenses through the distance reference point the mires are quite often fuzzy (usually plus powers). If I insert a 3^ axillary prism the mires tend to become clear. We use mostly Hoya products, but this occurs with others as well.

Thanks and please forgive my lack of knowledge.

[MakeOptics]

Hopefully someone can educate me on this issue.
When I neutralize some progressive lenses through the distance reference point the mires are quite often fuzzy (usually plus powers). If I insert a 3^ axillary prism the mires tend to become clear. We use mostly Hoya products, but this occurs with others as well.

Thanks and please forgive my lack of knowledge.

Chromatic Aberration, you effectively neutralize it when you place your prism in the lensmeter. If the lens has no prism thinning the the optical center is ground at the prism reference point, if your progressive is on average 4mm above this point at fit and the distance reference point is another 3mm to 4mm above that point, then you are a total of 7mm to 8mm off axis and will experience some prism. If prism thinning is included again using some assumptions lets say a 2.00 add, the amount of prism thinning is going to be roughly 2/3 or 1.33^D and the orientation is going to be base down, on a plus lens you are going to be 7mm to 8mm off axis and add that additional 1.33^D you would compound the issue.

[optical24/7]

Chromatic Aberration, you effectively neutralize it when you place your prism in the lensmeter. If the lens has no prism thinning the the optical center is ground at the prism reference point, if your progressive is on average 4mm above this point at fit and the distance reference point is another 3mm to 4mm above that point, then you are a total of 7mm to 8mm off axis and will experience some prism. If prism thinning is included again using some assumptions lets say a 2.00 add, the amount of prism thinning is going to be roughly 2/3 or 1.33^D and the orientation is going to be base down, on a plus lens you are going to be 7mm to 8mm off axis and add that additional 1.33^D you would compound the issue.

MO, specifically, isn't is LCA's (prism and abbe) that you are referring to?