Studies of intraocular plasma shielding during corneal laser surgery

Laser intrastromal ablation for refractive surgery bas been accomplished with ultrashoit-pulse lasers operating at multi-kHz pulse repetition frequencies to produce optical breakdown and plasma formation to cut within the corneal stroma. The focused laser beam can move in a controlled pattern over a desired corneal area to produce a clean flap for laser refractive surgery. To determine the safety of exposure of other ocular structures such as the lens and retina, a determination of the irradiance behind the optical plasma are required. Plasma shielding absorbs (and scatters) almost all of the incident energy in this surgical application and optical breakdown and optical plasma generation produce tissue vaporization, allowing only a small fraction of the incident energy to be transmitted through the plasma. In this safety study, measurements were performed at the retinal plane in a simulated eye and a retinal simulant was used to demonstrate the safety of the retinal exposure for a sub-nanosecond laser. It is shown that this procedure does not pose a hazard to other ocular tissues.Laser intrastromal ablation for refractive surgery bas been accomplished with ultrashoit-pulse lasers operating at multi-kHz pulse repetition frequencies to produce optical breakdown and plasma formation to cut within the corneal stroma. The focused laser beam can move in a controlled pattern over a desired corneal area to produce a clean flap for laser refractive surgery. To determine the safety of exposure of other ocular structures such as the lens and retina, a determination of the irradiance behind the optical plasma are required. Plasma shielding absorbs (and scatters) almost all of the incident energy in this surgical application and optical breakdown and optical plasma generation produce tissue vaporization, allowing only a small fraction of the incident energy to be transmitted through the plasma. In this safety study, measurements were performed at the retinal plane in a simulated eye and a retinal simulant was used to demonstrate the safety of the retinal exposure for a sub-nanosecond laser. It...