Vitreous opacities affect scanning laser polarimetry measurements

PURPOSE: To assess the effect of vitreous opacities on retinal nerve fiber layer retardation measurements obtained during scanning laser polarimetry. METHODS: Scanning laser polarimetry was performed in two eyes of two patients with vitreous opacities. RESULTS: The presence of a vitreous opacity within the measurement ellipse during scanning caused a marked, localized increase in polarization in the area of the opacity. This falsely increased the value obtained for the mean retinal nerve fiber layer thickness. Retinal nerve fiber layer thickness values were reduced when the opacity was not incorporated into the measurement ellipse. CONCLUSION: Artifact introduced by the presence of vitreous opacities can affect scanning laser polarimetry measurement reliability. (Am J Ophthalmol 2001;131: 511-513. (C) 2001 by Elsevier Science Inc. All rights reserved).