Some corneal disease’s must be cultured in order to know the infecting bug, and some presentations may seem infectious although they are not. Understanding presentation vs. pain can help you to make a diagnosis.
Reported pain worse than corneal presentation
1. Acanthomeba infection
2. Superior Limbic Keratoconjunctivitis (SLK)
Presentation of cornea worse than reported pain
1. Nuerotrophic Keratitis
2. Fungal Keratitis
Remember that these are generalities and not steadfast rules, you can use them to point you in the right direction.