Macular pigmentary alterations after repeated viewing of argon laser trabeculoplasty

We evaluated retinal morphologic and visual functional changes in two individuals accidentally exposed to argon laser "flashback" from an incorrectly placed laser protective filter while viewing a routine argon laser trabeculoplasty. These exposures, measured in the absence of a patient's eye, are in the region of the maximal permissible exposure (MPE). The patients were followed with serial visual function testing, scanning laser ophthalmoscopy (CSLO) and chromatic contrast sensitivity. The first individual received 54 monocular exposures. Acute examination revealed inferior and central Amsler grid abnormalities. These distortions matched the CSLO evidence of pigmentary changes in the corresponding retinal field. Initial contrast sensitivity showed high spatial frequency loss which increased during the ensuring 1.5 months. Chromatic contrast sensitivity revealed high spatial frequency loss for long wavelength test targets ("yellow") and broad spatial frequency loss with short wavelength targets ("blue"). The second individual received fewer exposures (4-6) bilaterally. Both eyes showed foveal morphologic alterations with non-selective changes in Moreland anomaloscopic matches, indicative of macular edema. We have shown a correlation between ophthalmoscopic and functional measures of spatial vision. Progressive loss in contrast sensitivity and spatial chromatic functional loss were associated with the more severe exposure while minimal changes were observed with fewer exposures.