My eyesight is about -10 and i enquired at Tesco optician yesterday about the cost of getting sunglasses into prescription sunglasses and also to be thinned.
I normally have the highest level of thinning. She said for sunglasses they recommend really only the lowest level of thinning, possibly mid level. But the more thinning you have the worse the tint will be.
She slowed me what a -6 would look like at mid level thinning and Even at mid level of thinning it was quite thick and she said that a -10 would be quite a bit worse.
Is this going to be the same everywhere? I do wear contacts and non prescription sunglasses but I can't read in my contacts.