Accidental Human Retinal Injuries by Laser Exposure: Implications to Laser Safety

摘要

In the past several years, the USAMRD has evaluated several laser accident/incident cases. The accidents generally occurred at close range from q-switched laser systems and resulted in retinal injury with visual function loss with varying degrees of recovery. The time course of the ophthalmoscopic consequences of the injuries was evaluated by conventional and scanning laser ophthalmoscopy (SLO). Functional evaluations included Snellen visual acuity, Amsler Grid, threshold visual fields, contrast sensitivity, color discrimination tests and performance of a pursuit tracking task. The clinical results and situational assessments of five exposure incidents are described. Five cases involved single or multiple exposures to q-switched neodymium (4) and ruby (1) laser radiation. All exposures were within 5 degrees of the fovea, yet none directly in the foveola. All patients reported subjective central vision loss in the acute phase. In one patient the visual acuity recovered from 20/60 at one week to 20/25 in four months with minimal central visual field loss. Three patients showed little to no recovery measured at 12 months with suppression of both high and low spatial frequency contrast sensitivity. Deep retinal scar formation and retinal traction were evident in two cases with vitreous hemorrhage. Nerve fiber layer damage to the papillo-macular bundle was clearly evident by SLO in one case. Visual performance measured with a pursuit tracking task revealed significant performance loss relative to normal tracking observers. Recovery from accidental laser eye injury depends on the exposure dose and location of the injury site within the retina and the potential for complicating secondary effects (e.g. scar formation, nerve fiber loss). When secondary effects are minimal, recovery to normal or near normal visual acuity may occur modified by ocular-motor processes that shift the preferred retinal location superior and slightly temporal to the fovea.