Polarimetric measurement of retinal nerve fiber layer thickness in glaucoma diagnosis

Purpose: To evaluate reliability and diagnostic value of polarimetric measu rements of the retinal nerve fiber layer (RNFL) thickness in the diagnosis of glaucoma. Methods: The study included 81 eyes with perimetric glaucoma with glaucomat ous changes of the optic disc and visual field defects; 52 eyes with preper imetric glaucoma with glaucomatous optic disc abnormalities and normal achr omatic visual fields; and 70 normal eyes. For determination of reliability, four examiners repeated polarimetric measurements five times in ten normal subjects. Results: The polarimetric variables were significantly correlated with incr easing mean visual field defect and decreasing neuroretinal rim area. In co rrelation analyses with visual field defects, correlation coefficients were highest for the variable "superior/nasal ratio" and "the Number," a variab le calculated by the neural network of the device. In correlations with neu roretinal rim area, correlation coefficients were highest for measurements of the inferior nerve fiber layer thickness. The preperimetric glaucoma gro up and the control group differed significantly in the variables "superior/ nasal ratio" and "the Number" and, to a smaller degree, in the variables "s uperior/temporal ratio" and "superior/inferior ratio." The Number variable had a sensitivity of 82% and 58% at a predefined specificity of 80% in sepa rating perimetric glaucoma patients and preperimetric glaucoma patients, re spectively, from control subjects. Reproducibility of the polarimetric meas urements ranged between 70% and 89%. Conclusion: Polarimetric measurements of the RNFL thickness can detect glau comatous optic nerve damage in patients with visual field loss, and in some patients with preperimetric glaucomatous optic nerve damage. Considering t he fast performance, easy handling, and low maintenance costs, RNFL polarim etry may be helpful in glaucoma diagnosis.