Ask yourself, how much does a damaged part or quality escape cost? Now how much does an eye exam cost?
It may not be a requirement but it certainly is a best practice.
I do know of one prime aerospace manufacturer that requires inspectors and operators to be tested. However, they don't require "machine attendants" to be tested. It depends on you define operator or attendant in your organization.
You can purchase an eye test chart online and test them yourself to get a decent gage as to their ability to see fine detail. Better yet, I'd check your companies medial insurance. It's quite possible they are already paying for an eye exam that your operators/inspectors might not be taking advantage of. Bifocal safety glasses with various magnification levels are available from various sources as well.
