Quantitative nerve fiber layer measurement using scanning laser polarimetry and modulation parameters in the detection of glaucoma.

PURPOSE

To assess a new method of processing quantitative nerve fiber layer (NFL) measurement data to distinguish between eyes with glaucoma of varying severity and normal eyes, using information obtained by scanning laser polarimetry.

PATIENTS AND METHODS

Scanning laser polarimetry measurements of the peripapillary NFL within a 10-pixel band located 1.8 disc diameters from and concentric with the disc margin were obtained from 36 normal eyes, 69 eyes with glaucoma, 7 eyes suspected of being glaucomatous, and 19 eyes with ocular hypertension. These values then were examined using new data processing "modulation" parameters in which the average of the nasal and temporal minimum retardation is subtracted from the retardation in the superior or inferior region of the peripapillary NFL. The ability of modulation parameters to differentiate between normal and glaucomatous eyes was compared with other parameters based either on the sum of retardation values in the superior or inferior region, or on the ratio of values in the superior or inferior region to the nasal region.

RESULTS

Differences in mean polarimetric retardation between normal eyes and eyes with glaucoma were significant for all parameters, but were greatest when modulation parameters were used and were significantly greater for two modulation parameters. The range of values showed considerable overlap between all groups of eyes. Eyes with ocular hypertension had mean values intermediate between normal eyes and eyes with early glaucomatous damage.

CONCLUSION

The use of new modulation parameters increases the ability of quantitative NFL measurement to distinguish between eyes with glaucoma of varying severity and normal eyes.