CLINICAL-EVALUATION OF SCANNING LASER POLARIMETRY - II - POLAR PROFILE SHAPE-ANALYSIS

Aims-To devise a method to describe and quantify the shape of polar pr ofiles obtained with the scanning laser polarimeter and to compare thi s measurement with other polar profile measurements in a series of nor mal subjects and glaucoma patients. Methods-Scanning laser polarimetry was performed on 54 normal subjects and 74 glaucoma patients. The ret ardation values obtained from one randomly chosen eye of each subject were analysed using our own methods, including the use of an algorithm to remove blood vessels from the polar profiles, an algorithm to stan dardise the glaucoma profiles to a normal database, and a further algo rithm to evaluate the profile shape. The measurements of profile shape were compared with measurements of the absolute and standardised reti nal nerve fibre layer thickness obtained with the scanning laser polar imeter. Results-There was no significant difference between the mean r etardation values for the normal and glaucomatous subjects in either h emiretina. However, standardisation of the glaucoma retardation values to a normal database produced significant differences at p <1 x 10(-8 ) in the mean retardation values for these two groups in both hemireti nas. Profile shape measurement analysis produced similar significant d ifferences between the mean retardation values for the normal and glau comatous subjects in both hemiretinas, although the degree of separati on was greater following standardisation of the retardation values. Co nclusion-The use of an algorithm to standardise an individual's retard ation values in conjunction with a blood vessel removal algorithm enab les an improvement in the ability of the scanning laser polarimeter to discriminate between normal and glaucomatous patients. The polar prof ile shape algorithm is independent of standardisation and significantl y improves the discrimination between normal and glaucomatous patients , as well as providing additional information regarding the retinal ne rve fibre layer.