Ablation of subretinal tissue with optical fiber delivered 266 nm laser pulses.

摘要

New and more precise subretinal surgical techniques would be useful in a range of retinal diseases. The purpose of this study is to determine the feasibility of using fiberoptically delivered ultraviolet laser energy to transect or ablate subretinal tissues. Choroid segments dissected from fresh porcine eyes, with or without the retinal pigment epithelium (RPE), were clamped in a fluid bath. Pulsed fourth harmonic (266 nm) of a Nd:YAG laser radiation was delivered via an optical fiber probe at fluence levels between 0.08 and 0.40 J/cm(2). The tissue was then fixed and sectioned for histological examination. Radiation induced damage was categorized by the degree of tissue disruption and ablation depth. Tissue ablation and the severity of the tissue injury varied with both tissue properties and applied laser parameters. Disruption of Bruch's membrane was typically induced by 10 pulses of 0.30 J/cm(2) or 2 pulses of 0.40 J/cm(2). Lower radiation doses did not disrupt Bruch's membrane, but did damage the choroidal tissue and produce vacuoles in the underlying choroid. The full thickness of the choroid was ablated by 200 pulses of 0.40 J/cm(2). The presence of the RPE produced a shielding effect which was greater than would be expected for an equivalent thickness of choroidal tissue. Ablation characteristics of subretinal tissue are highly dependent on the laser parameters used and the type of tissue involved. To perform well controlled laser surgery on subretinal tissues both laser parameters and the properties of the target cells and tissues have to be considered.