ECHOGRAPHIC MEASUREMENT OF OPTIC-NERVE THICKNESS CORRELATED WITH NEURORETINAL RIM AREA AND VISUAL-FIELD DEFECT IN GLAUCOMA

PURPOSE: To determine whether echographic measurements of the pial dia meter of the optic nerve are significantly correlated with glaucomatou s changes of the optic disk and retinal nerve fiber layer. METHODS: In 31 patients with primary open-angle glaucoma and 16 normal control su bjects, optic nerve thickness was determined by measuring the maximal pial diameter of the optic nerve using standardized A-scan echography. The optic disks were morphometrically examined using color stereo pho tographs, and the retinal nerve fiber layer was assessed using wide-an gle red-free fundus photographs. RESULTS: Optic nerve thickness as mea sured echographically decreased significantly (P <.001) with decreasin g neuroretinal rim area, diminishing visibility of the retinal nerve f iber layer, narrowing of the retinal arterioles, enlarging para-papill ary atrophy, and increasing mean visual field defect. In an intraindiv idual bilateral comparison, side differences in the optic nerve thickn ess were significantly correlated with side differences in neuroretina l rim area (P <.0001), diameter of retinal arterioles (P =.003), and v isual field defect (P <.0001). In the differentiation of normal and gl aucomatous eyes, sensitivity and specificity were higher for echograph ic measurements of the optic nerve thickness than for parapapillary at rophy and diameter of retinal arterioles but worse than for determinat ion of the neuroretinal rim area. CONCLUSIONS: Echographic measurement s of optic nerve thickness are significantly correlated with glaucomat ous changes of the optic disk and retinal nerve fiber layer. In patien ts with opaque media, echographic measurement of optic nerve thickness may be helpful in distinguishing among normal eyes, eyes with medium advanced glaucoma, and eyes with markedly progressed glaucoma.