[Photo damage to the eye in exposure to the radiation from a Nd:YAG Q-switching laser: the physicochemical structural changes to the crystalline lens and the vitreous body].

Structural changes in the lens and vitreous body exposed to short-pulse Nd:YAG Q-switching laser were under study. The laser was focussed in the lens nucleus or vitreous center plane. A pulse energy was 7.1-9.3 mJ, with a total of 75-100 pulses. Cataract development was induced via the formation of cavities with the guidance spot focal plane localized in the lens nucleus plane. When the focus was in the vitreous body and the laser operated in a similar energy mode, great numbers of small cavities rapidly formed, this evidencing a shock wave propagation. Specific and structural conformational changes in the lens and vitreous protein molecules were detected by nitrate quenching of the triptophane amino acid residue fluorescence. Laser exposure was found to reduce triptophanile availability for nitrates, this evidencing protein complexes aggregation (collapse); besides, laser exposure essentially increased the amino acid residue quenching constants, which fact pointed to a decreased density of the vitreous collagen and lens crystalline negative charges (increased hydratation). These findings permit a conclusion that the shifts connected with injury to the vitreous body, with macular edema, or with detachment of the retina after exposure to Nd:YAG laser may be due to collapse of the vitreous gel liquified components.