One of my friends in states answered my question the other day. I post her answer here. From the answers and comments I got I start to realize maybe this is another culture difference I never think of before.
How is your eyesight would be the correct way to ask, but we do not ask other people that question unless there is a specific need to ask.
No one would ever ask someone here "What is your eyesight". So forget that phrase entirely. If someone sees you are having trouble reading, they might ask if they need reading glasses. We do not ever have any conversation in general about eyesight. Someone might say, "I have to get a new prescription for my glasses today so I will be at the eye doctor's all afternoon", to tell what they are doing. We would only ask if the conversation went to the topic of two people with problems wanting to talk about maybe who their doctor is or where they buy their glasses or might exclaim, "Oh, I can hardly see this. I might need a new prescription."
Rarely would you ever ask if someone is near-sighted or far-sighted. I have never asked anyone that in my life nor have they asked me. You certainly would never talk about what your prescription actually is about the diopter or whatever the word was that you used. We would never in any case at all go into the technicalities of our prescription because none of us know it. We just don't talk about it here and if someone tried to have a chatty conversation with you , that would never be the topic.
How is your eyesight would be the correct way to ask, but we do not ask other people that question unless there is a specific need to ask.
No one would ever ask someone here "What is your eyesight". So forget that phrase entirely. If someone sees you are having trouble reading, they might ask if they need reading glasses. We do not ever have any conversation in general about eyesight. Someone might say, "I have to get a new prescription for my glasses today so I will be at the eye doctor's all afternoon", to tell what they are doing. We would only ask if the conversation went to the topic of two people with problems wanting to talk about maybe who their doctor is or where they buy their glasses or might exclaim, "Oh, I can hardly see this. I might need a new prescription."
Rarely would you ever ask if someone is near-sighted or far-sighted. I have never asked anyone that in my life nor have they asked me. You certainly would never talk about what your prescription actually is about the diopter or whatever the word was that you used. We would never in any case at all go into the technicalities of our prescription because none of us know it. We just don't talk about it here and if someone tried to have a chatty conversation with you , that would never be the topic.