I should clarify that I know glasses don't help blindness, so I mean before glasses and wider societal support for blind people
This answer by /u/BaffledPlato partly answers your question:
While this may not directly answer your question, an interesting factoid about early optometry is that the stars were often used as eye tests: If someone couldn't distinguish two stars very close to each other, such as the double star Alcor and Mizar or the big dipper, they had very poor vision and could not be trusted with tasks requiring keen eyesight.
This doesn't really answer how people with poor eyesight were treated, but it does answer how they were identified.
Source:
An Ancient Eye Test-Using the Stars, George M. Bohigian M.D., Survey of Ophthamology