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Q&A Why would a 1.74 index lens be more prone to chip and be less resilient than 1.67?

My optician counselled me I don't recommend a 1.74 index with a metal grooved frame, like the one you want from ic! Berlin, because the edge will be less resilient and be more susceptible to chi...

1 answer  ·  posted 3y ago by TextKit‭  ·  last activity 3y ago by Olin Lathrop‭

Question lenses
#3: Post edited by user avatar TextKit‭ · 2021-02-25T17:17:06Z (over 3 years ago)
  • My optician counselled me
  • >I don't recommend a 1.74 index with a metal grooved frame, like the one you want from ic! Berlin, because the edge will be less resilient and be more susceptible to chipping.
  • Please explain like I'm 5 years old, because I don't know physics or opticianry. I tried to google but I don't understand the results. Why's [1.74 more brittle? Why does "chipping along the groove" mean](https://old.reddit.com/r/glasses/comments/9ow8a1/lindberg_air_titanium_rim_and_strong_prescription/e7xnelt/)? What does ["thinning"](https://reddit.com/r/optometry/comments/252srt/are_hiindex_lenses_a_marketing_gimmick/chd4qwd/) mean?
  • >Think of lenses as having 4 levels of thinning; Basic 1.49, 1.59/1.60, 1.66/7, and 1.74.
  • Why would [1.74 be too fragile? Why a lot of stress on the lenses for metal groove frames like those](https://reddit.com/r/optometry/comments/2abvyc/high_index_lenses_600_on_ultra_light_framesmykita/citkgcz/)?
  • >1.74 will most likely chip and break especially along the edges of the groove.
  • My optometrist, different person, diagnosed me with nearsightedness. His prescription shows
  • >OD –6.00 (Sphere), –1 (Cylinder).
  • >OS –7.00, –1.
  • My optician counselled me
  • >I don't recommend a 1.74 index with a metal grooved frame, like the one you want from ic! Berlin, because the edge will be less resilient and be more susceptible to chipping.
  • Please explain like I'm 5 years old. I don't know physics or opticianry. Why's [1.74 more brittle? Why does "chipping along the groove" mean](https://old.reddit.com/r/glasses/comments/9ow8a1/lindberg_air_titanium_rim_and_strong_prescription/e7xnelt/)? What does ["thinning"](https://reddit.com/r/optometry/comments/252srt/are_hiindex_lenses_a_marketing_gimmick/chd4qwd/) mean?
  • >Think of lenses as having 4 levels of thinning; Basic 1.49, 1.59/1.60, 1.66/7, and 1.74.
  • Why would [1.74 be too fragile? Why a lot of stress on the lenses for metal groove frames like those](https://reddit.com/r/optometry/comments/2abvyc/high_index_lenses_600_on_ultra_light_framesmykita/citkgcz/)?
  • >1.74 will most likely chip and break especially along the edges of the groove.
  • My optometrist, different person, diagnosed me with nearsightedness. His prescription shows
  • >OD –6.00 (Sphere), –1 (Cylinder).
  • >OS –7.00, –1.
#2: Post edited by user avatar TextKit‭ · 2021-02-25T17:16:20Z (over 3 years ago)
  • Why would a 1.74 index lens be more probable to chip and be less resilient than 1.67?
  • Why would a 1.74 index lens be more prone to chip and be less resilient than 1.67?
  • My optometrist diagnosed me with nearsightedness. His prescription shows
  • >OD –6.00 (Sphere), –1 (Cylinder).
  • >OS –7.00, –1.
  • My optician, different person, counselled me
  • >I don't recommend a 1.74 index with a metal grooved frame, like the one you want from ic! Berlin, because the edge will be less resilient and be more susceptible to chipping.
  • Please explain like I'm 5 years old, because I don't know physics or opticianry. I tried to google but I don't understand the results. Why's [1.74 more brittle? Why does "chipping along the groove" mean](https://old.reddit.com/r/glasses/comments/9ow8a1/lindberg_air_titanium_rim_and_strong_prescription/e7xnelt/)? What does ["thinning"](https://reddit.com/r/optometry/comments/252srt/are_hiindex_lenses_a_marketing_gimmick/chd4qwd/) mean?
  • >Think of lenses as having 4 levels of thinning; Basic 1.49, 1.59/1.60, 1.66/7, and 1.74.
  • Why would [1.74 be too fragile? Why a lot of stress on the lenses for metal groove frames like those](https://reddit.com/r/optometry/comments/2abvyc/high_index_lenses_600_on_ultra_light_framesmykita/citkgcz/)?
  • >1.74 will most likely chip and break especially along the edges of the groove.
  • My optician counselled me
  • >I don't recommend a 1.74 index with a metal grooved frame, like the one you want from ic! Berlin, because the edge will be less resilient and be more susceptible to chipping.
  • Please explain like I'm 5 years old, because I don't know physics or opticianry. I tried to google but I don't understand the results. Why's [1.74 more brittle? Why does "chipping along the groove" mean](https://old.reddit.com/r/glasses/comments/9ow8a1/lindberg_air_titanium_rim_and_strong_prescription/e7xnelt/)? What does ["thinning"](https://reddit.com/r/optometry/comments/252srt/are_hiindex_lenses_a_marketing_gimmick/chd4qwd/) mean?
  • >Think of lenses as having 4 levels of thinning; Basic 1.49, 1.59/1.60, 1.66/7, and 1.74.
  • Why would [1.74 be too fragile? Why a lot of stress on the lenses for metal groove frames like those](https://reddit.com/r/optometry/comments/2abvyc/high_index_lenses_600_on_ultra_light_framesmykita/citkgcz/)?
  • >1.74 will most likely chip and break especially along the edges of the groove.
  • My optometrist, different person, diagnosed me with nearsightedness. His prescription shows
  • >OD –6.00 (Sphere), –1 (Cylinder).
  • >OS –7.00, –1.
#1: Initial revision by user avatar TextKit‭ · 2021-02-25T17:14:18Z (over 3 years ago)
Why would a 1.74 index lens be more probable to chip and be less resilient than 1.67?
My optometrist diagnosed me with nearsightedness. His prescription shows

>OD –6.00 (Sphere), –1 (Cylinder).   
>OS –7.00, –1. 

 My optician, different person, counselled me 

>I don't recommend a 1.74 index with a metal grooved frame, like the one you want from ic! Berlin, because the edge will be less resilient and be more susceptible to chipping.

Please explain like I'm 5 years old, because I don't know physics or opticianry. I tried to google but I don't understand the results. Why's [1.74 more brittle? Why does "chipping along the groove" mean](https://old.reddit.com/r/glasses/comments/9ow8a1/lindberg_air_titanium_rim_and_strong_prescription/e7xnelt/)? What does ["thinning"](https://reddit.com/r/optometry/comments/252srt/are_hiindex_lenses_a_marketing_gimmick/chd4qwd/) mean?

>Think of lenses as having 4 levels of thinning; Basic 1.49, 1.59/1.60, 1.66/7, and 1.74.

Why would [1.74 be too fragile? Why a lot of stress on the lenses for metal groove frames like those](https://reddit.com/r/optometry/comments/2abvyc/high_index_lenses_600_on_ultra_light_framesmykita/citkgcz/)?

>1.74 will most likely chip and break especially along the edges of the groove.