Fig. 2: Comparison of normal and edematous corneal ablation by employing the mid-infrared (MIR) fs laser resonating with the amide-I mode and the conventional near-infrared (NIR) fs surgical laser.
From: In vivo keratotomy by mid-infrared femtosecond laser resonant with amide vibrational mode
a The measured Fourier transform infrared (FTIR) absorption spectrum of corneal tissue. The resonance modes are marked above the absorption peaks. Photos (b–e), (j–m) and corresponding histological images (f–i), (n–q) of corneal incisions under different laser wavelengths and pulse energy. b, f When corneal ablation is performed at a wavelength of 6.1 μm with a pulse energy of 2 μJ, a sharp penetrating incision with a depth of ~110 μm is formed. c, g As the laser wavelength is switched to 1.03 μm, with 3 μJ pulse energy, only a shallow scratch with an epithelial ablation depth of ~20 μm is observed. d, h Further increasing the pulse energy of the 1.03 μm femtosecond laser to 16 μJ deepens the incision, however, severe collateral damage with a rough incision and a large denaturation zone is caused. e When the focus of 1.03 μm laser with 16 μJ pulse energy slightly drifts away from the corneal surface, thermal shrinkage of corneal epithelium is observed, and significant irreversible damage to iris and lens is caused. j, n Penetrating incision can still be formed in edematous cornea with 6.1 μm laser. k, o 1.03 μm laser with 3 μJ energy fails to create deep incision, but only causes collateral thermal damage around the incision. l, p Further increasing the pulse energy to 16 μJ resulting in a deeper incision while causing severe corneal collateral damage and deformation of lens. m, q Intact edematous cornea. The incisions are marked by white arrows.
