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 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? What does "thinning" mean?
Think of lenses as having 4 levels of thinning; Basic 1.49, 1.59/1.60, 1.66/7, and 1.74.
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.