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 patien ts 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 v alues were reduced when the opacity was not incorporated into the measureme nt ellipse. CONCLUSION: Artifact introduced by the presence of vitreous opacities can a ffect scanning laser polarimetry measurement reliability. (Am J Ophthalmol 2001;131: 511-513. (C) 2001 by Elsevier Science Inc. All rights reserved).