Gradient-index (GRIN) lens multimode fiber probe for laser-induced breakdown in the eye

摘要

A model laser surgical probe was designed and built to employ laser induced breakdown (LIB) in cutting fibrovascular membranes within the vitreous cavity of the eye. The probe is a simple design of a gradient index (GRIN) lens attached to the tip of a multimode fiber. It is designed to fit through a sclerotomy incision and enter the vitreaous cavity for work anterior to the retina. The laser light is focused close to the tip of the probe without causing GRIN lens damage. Thus a widely divergent beam behind the focus will diminish potential laser damage posterior to the target tissue. A Nd:YAG 1064-nm 10-ns pulsed laser was used with the probe inserted into a cell of tap water. Threshold data for laser induced breakdown was taken ad fit to a probit curve. The data was compared with past LIB threshold data. The radiant exposure versus distance from the probe was plotted via spot size measurements. This measurement gave a rough indication of the distance the probe must remain from the retina to be well below retinal maximum permissible exposure (MPE) levels. In-vitro threshold measurements of bovine vitreous were taken and compared to the water threshold. Finally, collagen membranes were lased with the probe to demonstrate its functional application.