
What breed and eye conditions are we tsalking about. Sadly very few eye conditions can have a clear result, as most are inherited as recessives.
The eye test can tell you if a parent is affected or unaffected. For conditions that are late onset a dog may be unaffected and a year or so later could still end up affected.
The only way to tell carriers is in the very few condiitons for which a DNA test is available, and even then they are not a 100% if they are a marker test as opposed to the actual gene.