Quote Originally Posted by misslindsay View Post
Honestly? I think my real problem is not giving new lenses with a significant size, base curve, material, and Rx change from my old specs enough time before b*tching about them. I'm fully willing to admit to that. Okay? But I still don't regret the choice to go with the 1.67s -- the lens is honestly thick enough at the lateral sides for me to be thankful I chose them, despite the chromatic aberrations.

You could have had your cake and ate it too, a 1.60 in your power with a 50mm lens decentered 3mm would have a thickness of 4.4mm, the 1.67 has a thickness of 4.1mm, a negligible difference to me anyway. The effect of Ch.Ab that is noticeable is 0.1, in 1.60 with an Abbe of 42 compared to a 1.67 with an Abbe of 32.

1.67 Material:
0.1 = Prism / 32
Prism = 3.2

1.60 Material:
0.1 = Prism / 42
Prism = 4.2

Your prescription (4.25) in 1.67:
3.2 = 4.25 * decentration
decentration = 0.75cm = 7.5mm

Your prescription (4.25) in 1.60:
4.2 = 4.25 * decentration
decentration = 0.99cm = 9.9mm

Rotation of the eye in 1.67 to reach this point in the lens:
tan(rotation) = 7.5 / 30
tan(rotation) = 0.25
rotation = 14.0 degrees

Rotation of the eye in 1.60 to reach this point in the lens:
tan(rotation) = 9.9 / 30
tan(rotation) = 0.33
rotation = 18.3 degrees

Most lens designers try and reduce the effects of monochromatic aberrations for a field of 30 degrees, in the case of chromatic aberration the lens choice is gonna effect the visual acuity even before reaching that 30 degrees, 1.67 is a good material for what it is a high index lens, but in this case it could be argued that the significance of 0.3mm in reduced thickness isn't worth the overall 8.6 degrees of lost field associated with the lens. It's not important to remember the math, just the concept a better Abbe is going to be the best choice in most cases of moderate power, it's only when we get into high powers that the benefits of 1.67 out weight the 1.60, luckily now their are other options as well like 1.70 and even 1.74 which both have a better Abbe than poly and 1.67. Hope that helps you better understand why the choice of a better Abbe material, my guess is that you'll get used to it either way. In the future though you'll make a choice for a better Abbe and still won't notice the difference until you decide to go backwards to the 1.67 from the better choice then it will become more apparent.