What does 'eye-clean' mean for a lab-grown diamond?

An eye-clean diamond has no inclusions visible to the unaided eye when viewed face-up under normal lighting conditions. The standard test is to hold the stone at a natural viewing distance, roughly 25-30 cm, and scan it from the table down; if no clarity features are detectable, the diamond qualifies as eye-clean. What matters in practice is that eye-clean status depends on the observer: a trained gemologist actively hunting for inclusions will spot features that a casual viewer never would.