All intraocular solutions should be essentially free from particles that can be observed on visual inspection using Visible Particulates in Injections 〈790〉, as directed by Ophthalmic Products—Quality Tests 〈771〉. Additionally, certain injection products require subvisible particulate matter testing by Particulate Matter in Injections 〈788〉 or 〈771〉. The tests described in this chapter are physical tests performed for the purpose of enumerating subvisible particles within specific size ranges.