We are grateful to Dr Berger for pinpointing an important concept, which was possibly understated in our article,1 ie, the distinction between subthreshold and above threshold interaction. Dr Berger's example is also helpful to clarify the ablation process occurring in hydrated solid tissues with Er-YAG radiation at 10 J/cm2 radiant exposure and 200-microsecond pulse length.
Azzolini C, Gobbi PG, Brancato R. Erbium-YAG Laser Ablation: The Myth of 1-µm Penetration—Reply. Arch Ophthalmol. 1998;116(6):830-831. doi: