Slope of the peripapillary nerve fiber layer surface in glaucoma.

PURPOSE

To develop structural markers of early glaucomatous optic nerve damage with confocal scanning laser ophthalmoscopy.

METHODS

Custom software was developed to analyze the images of 53 patients with open-angle glaucoma and 43 healthy subjects (matched for age, race, and refractive error), with images acquired with a confocal scanning laser ophthalmoscope. Height values were obtained along radial profiles of the peripapillary nerve fiber layer surface at 5-degree intervals around the disc edge. Two new parameters were derived: mean height and mean slope of the peripapillary nerve fiber layer surface. Mean slope was tested for its independence from a retinal reference plane. A logistic regression analysis was used to determine functions of disease probability. Receiver-operating characteristic (ROC) curves were used to evaluate sensitivity and specificity of peripapillary nerve fiber layer slope and height to discriminate normal subjects from glaucoma patients.

RESULTS

Mean (+/-SD) visual field mean deviation in the glaucoma group was -4.8 +/- 3.3 dB. Mean slope (+/-SD) of the peripapillary nerve fiber layer was significantly (P < 0.001) steeper (0.30 +/- 0.12) in glaucoma patients than in healthy subjects (0.11 +/- 0.12). Mean slope values were identical with or without the retinal reference plane. Mean height (+/-SD) values with respect to a retinal reference plane were 45.2 +/- 103 microm in healthy subjects and -65.2 +/- 105 microm in glaucoma patients, which were significantly different (P < 0.001). The differences for mean slope and for mean height between the healthy subjects and the glaucoma patients were greatest inferiorly. The diagnostic precision, sensitivity, and specificity of mean slope were 83%, 85%, and 80%, respectively. The diagnostic precision, sensitivity, and specificity of mean height were 75%, 69%, and 83%, respectively.

CONCLUSIONS

Mean peripapillary slope of the nerve fiber layer surface can be used to discriminate between healthy subjects and glaucoma patients with clinically useful diagnostic precision. This parameter is independent of a retinal reference plane and may be particularly useful to detect progressive glaucoma damage.