In America or Canada, two categories professions

In America or Canada, two categories professions provide the service. one is optometrist. the other is ophthalmologist.
But none of them must have the service since most of them are private practice.

In practice, optometrist ususally specialize in the service since they are trained in their professional education. ophthalmologist
may enter the service but they specialized in eye related diese and surgery.

there are some risks you may concern such as infection or broken eyeglass incident. If you use with caution, you can control
the risk and maxmize benefit.

在美国和加拿大，不是什么人都可以支付的起这种服务的，而且相关的条例很严格，所以使用的人群很有限，
出现的问题也很少，因为技术是过关的，

但是，中国因为是个迅速成长的大国，管理很烂，人群又大，因此出现的问题也就五花八门了，但这不说明OK竟
就有很大问题。