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I'm shocked at how thin those lenses are. I'm at -11.5 diopter and my edges are already >1cm thick. It sounds like it's one lens set entirely inside another one

I'm shocked at how thin those lenses are. I'm at -11.5 diopter and my edges are already >1cm thick. It sounds like it's one lens set entirely inside another one? Even using 1.8 index material the thinness is really impressive. I bet the chromatic abberation isn't, though. It's not 1-to-1 but generally the higher the refractive index the lower the Abbe number, the more colors get split apart.

lucb1e 4y ago
The concentric rings of increasing blurriness remind me of a Fresnel lens. I'm no optician and always found the physics of light rays confusing as heck so the only words I understand from the wikipedia aricle are "A Fresnel lens can be made much thinner than a comparable conventional lens, in some cases taking the form of a flat sheet." Maybe someone else can tell whether that's what's being used here? https://en.wikipedia.org/wiki/Fresnel_lens https://en.wikipedia.org/wiki/Fresnel_lens
- porphyra 4y ago
  I don't think it's a Fresnel lens. Fresnel lenses have rather obvious rings and have poor optical qualities for most applications besides light sources, cheap slide projectors, and magnifying glasses. Here, the "lens-within-a-lens" effect that you see is because, generally speaking, myopia lenses shrink the image. But this lens is so extreme that the image is shrunk into a small bubble in the middle. The ring-like structures around this bubble are due to internal reflections within the lens.
- Lanrei 4y ago
  The article says that they're biconcave, which means that the thinnest part of the lens is in the centre (similar to a red blood cell). For high-myopia lenses, they often remove the lens material away from the centre to limit the maximum thickness at the expense of reducing the field of view. The resulting surface is usually left unpolished, but the lens underneath will still bend light, resulting in the circular patterns you mentioned. In this case a very large amount of material is removed as they would be impossible to use with a conventional frame otherwise. The alternative would be to use glasses with very small lenses.
BrandoElFollito 4y ago
I am around -5 and it is stable; I think this is not far from the limit where wearing glasses starts to be annoying (chromatic aberration, distortions, ...). I could consider lenses but I am always wondering how air conditioning and the fact that I cover my eyes with some plastic works long term (well, I am 52 so it may not be that of a concern, finally :)). At some point I considered lasic surgery but wearing glasses still trumps the risk for me (this is really a personal opinion, I know people who are really happy with the change)
- benzoate 4y ago
  I recently had laser eye surgery and subsequently re-evaluated my relationship with glasses over the previous 15 years — obviously I was frustrated enough to get the surgery but hadn’t considered their impact holistically over my life. My feeling is that glasses are annoying from -1, but their impact is tolerated as being able to see is a net gain. If I had known of their existence beforehand I might have sought out Ortho-K lenses — you wear them whilst you sleep and then take them out for corrected vision during the day. They are more expensive than surgery in the long term (10+ years), but they are less invasive and might be something worth considering.
  - BrandoElFollito 4y ago
    So how would you rate that impact? Was surgery worth it? (it probably depends on your level of myopia)
    - boruto 4y ago
      Absolutely worth it. I feel I started seeing better than with glasses. But there is an absolute overall improvement in quality of everyday life. Should have done it a decade back.
    - benzoate 4y ago
      Same as Boruto, worth it without a doubt. The quality of vision is better than with glasses or contact lenses.

lucb1e 4y ago

The concentric rings of increasing blurriness remind me of a Fresnel lens. I'm no optician and always found the physics of light rays confusing as heck so the only words I understand from the wikipedia aricle are "A Fresnel lens can be made much thinner than a comparable conventional lens, in some cases taking the form of a flat sheet." Maybe someone else can tell whether that's what's being used here? https://en.wikipedia.org/wiki/Fresnel_lens https://en.wikipedia.org/wiki/Fresnel_lens

porphyra 4y ago
I don't think it's a Fresnel lens. Fresnel lenses have rather obvious rings and have poor optical qualities for most applications besides light sources, cheap slide projectors, and magnifying glasses. Here, the "lens-within-a-lens" effect that you see is because, generally speaking, myopia lenses shrink the image. But this lens is so extreme that the image is shrunk into a small bubble in the middle. The ring-like structures around this bubble are due to internal reflections within the lens.
Lanrei 4y ago
The article says that they're biconcave, which means that the thinnest part of the lens is in the centre (similar to a red blood cell). For high-myopia lenses, they often remove the lens material away from the centre to limit the maximum thickness at the expense of reducing the field of view. The resulting surface is usually left unpolished, but the lens underneath will still bend light, resulting in the circular patterns you mentioned. In this case a very large amount of material is removed as they would be impossible to use with a conventional frame otherwise. The alternative would be to use glasses with very small lenses.

BrandoElFollito 4y ago

I am around -5 and it is stable; I think this is not far from the limit where wearing glasses starts to be annoying (chromatic aberration, distortions, ...). I could consider lenses but I am always wondering how air conditioning and the fact that I cover my eyes with some plastic works long term (well, I am 52 so it may not be that of a concern, finally :)). At some point I considered lasic surgery but wearing glasses still trumps the risk for me (this is really a personal opinion, I know people who are really happy with the change)

benzoate 4y ago
I recently had laser eye surgery and subsequently re-evaluated my relationship with glasses over the previous 15 years — obviously I was frustrated enough to get the surgery but hadn’t considered their impact holistically over my life. My feeling is that glasses are annoying from -1, but their impact is tolerated as being able to see is a net gain. If I had known of their existence beforehand I might have sought out Ortho-K lenses — you wear them whilst you sleep and then take them out for corrected vision during the day. They are more expensive than surgery in the long term (10+ years), but they are less invasive and might be something worth considering.
- BrandoElFollito 4y ago
  So how would you rate that impact? Was surgery worth it? (it probably depends on your level of myopia)
  - boruto 4y ago
    Absolutely worth it. I feel I started seeing better than with glasses. But there is an absolute overall improvement in quality of everyday life. Should have done it a decade back.
  - benzoate 4y ago
    Same as Boruto, worth it without a doubt. The quality of vision is better than with glasses or contact lenses.