Fourier analysis of nerve fiber layer measurements from scanning laser polarimetry in glaucoma: Emphasizing shape characteristics of the 'double-hump' pattern

Purpose: The pattern of the distribution of nerve fiber layer (NFL) thickne ss values across the retina may provide an early anatomic indication of gla ucomatous disruption. We developed a method of analyzing polarimetry measur ements that emphasizes the shape of the pattern of NFL thickness values. Se nsitivity and specificity for detecting glaucoma was obtained for these mea sures and compared with those for conventional measures. Methods: Nerve fiber thickness was inferred from retardation shift measured by a scanning laser polarimeter (Laser Diagnostic Technologies, Inc., San Diego, CA) in 34 healthy subjects (68 eyes) and 34 patients with glaucoma ( 68 eyes). Fourier analysis was performed on the polarimetry data to emphasi ze the shape in the evaluation of the distribution of thickness values arou nd the optic disc (along a 1.7-disc diameter ring). This was computed separ ately on superior and inferior hemiretinas. Results: Significant differences were found in the Fourier shape measures b etween healthy subjects and patients with glaucoma. The sensitivity and spe cificity using Four er coefficients with this particular sample was 96% and 90%, respectively. Conclusion: The evaluation of NFL measurements with Fourier analysis to emp hasize the holistic shape of the "double-hump" pattern was found to be a us eful tool as an analysis strategy.