Application of the nonlinear thermal ablation model to the chemical HF laser corneal ablation data gives the dropping of the effective absorption coefficients by two orders of magnitude relative to the native tissue. This effect is believed to be due to the hydrogen bond weakening at subthreshold fluences and to the homogeneous broadening removal by ablation products' expansion at higher fluences.
Nickolay P. Furzikov,
"Origin of corneal bleaching under chemical HF laser ablation", Proc. SPIE 1646, Laser-Tissue Interaction III, (7 August 1992); doi: 10.1117/12.137456; https://doi.org/10.1117/12.137456