Difference between revisions of Severe myopia

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There are disadvantages:

* Cost: Zeiss goes up to ''n''=1.9, but these lenses can cost around ~~250~~$ each at an optometrist.

* Cost: Zeiss goes up to ''n''=1.9, but these lenses can cost around $300 each at an optometrist.

* High refractive index glass is subject to much stronger reflections at the glass/air interfaces. You really need anti-~~reflection~~ coatings~~. But~~ these ~~don't~~ reduce reflections as much as they do for ~~regular~~ glass.

* High refractive index glass is subject to much stronger reflections at the glass/air interfaces. You really need [https://en.wikipedia.org/wiki/Anti-reflective_coating anti-reflective coatings], but these do not reduce reflections as much as they do for lower 'n'' glass.

* Chromatic ~~aberrations are markedly~~ worse ~~with highly~~ leaded glass[https://en.wikipedia.org/wiki/~~Chromatic_aberration~~]. This ~~becomes~~ particularly noticeable when looking off to the side through the lenses, close to their edges.

* [https://en.wikipedia.org/wiki/Chromatic_aberration Chromatic aberration] is worse since leaded glass has significantly more [https://en.wikipedia.org/wiki/Dispersion_(optics) dispersion] than regular glass. This is particularly noticeable when looking off to the side through the lenses, close to their edges, at a multi-color target such as an RGB LED.

When you have found a frame with very small diameter lenses, going for ''n''=1.7 or ''n''=1.8 might be good enough to keep the weight down and the edges thin. But the larger the lens diameter—and of course the stronger the lenses—the more necessary it becomes to keep the weight down and edge thickness under control by paying for the highest-''n'' lenses you can get.

@@ Line 24: / Line 24: @@
 There are disadvantages:
-* Cost: Zeiss goes up to ''n''=1.9, but these lenses can cost around 250$ each at an optometrist.
+* Cost: Zeiss goes up to ''n''=1.9, but these lenses can cost around $300 each at an optometrist.
-* High refractive index glass is subject to much stronger reflections at the glass/air interfaces. You really need anti-reflection coatings. But these don't reduce reflections as much as they do for regular glass.
+* High refractive index glass is subject to much stronger reflections at the glass/air interfaces. You really need [https://en.wikipedia.org/wiki/Anti-reflective_coating anti-reflective coatings], but these do not reduce reflections as much as they do for lower 'n'' glass.
-* Chromatic aberrations are markedly worse with highly leaded glass[https://en.wikipedia.org/wiki/Chromatic_aberration]. This becomes particularly noticeable when looking off to the side through the lenses, close to their edges.
+* [https://en.wikipedia.org/wiki/Chromatic_aberration Chromatic aberration] is worse since leaded glass has significantly more [https://en.wikipedia.org/wiki/Dispersion_(optics) dispersion] than regular glass. This is particularly noticeable when looking off to the side through the lenses, close to their edges, at a multi-color target such as an RGB LED.
 When you have found a frame with very small diameter lenses, going for ''n''=1.7 or ''n''=1.8 might be good enough to keep the weight down and the edges thin. But the larger the lens diameter—and of course the stronger the lenses—the more necessary it becomes to keep the weight down and edge thickness under control by paying for the highest-''n'' lenses you can get.