Purpose:
To determine the diagnostic power of peripalliary nerve fiber layer (NFL) reflectance for glaucoma diagnosis.
Methods:
Forty three normal eyes and 68 glaucomatous eyes were scanned with optical nerve head (ONH) scan using RTVue Fourier domain optical coherence tomography (Optovue, Fremont, CA). Three repeated scans were obtained for each eye. The patients were selected from university of southern California center subset of advance image for glaucoma study (AIGS). The OCT images were segmented with RTVue 6.1.0.4 software. Reflectance was averaged in NFL band and retina pigment epithelium (RPE) band for each a-scan. Then they were averaged in the superior and inferior quadrant of the outer three rings (diameter=4.9, 4.6 and 4.3mm). At last, the reflectance ratio between NFL and RPE (NFL/RPE reflectance ratio) was calculated. The difference between normal and glaucoma subjects were tested by t-test. The diagnostic power was evaluated with area under receiver operating characteristic curve (AROC) using the average of superior and inferior quadrant.
Results:
Both NFL and RPE reflectance showed significant difference between normal and glaucoma subjects (Table 1). But the difference was larger in NFL than RPE. The NFL/RPE reflectance ratio was also significantly lower in glaucomatous subjects. For diagnostic power, NFL/RPE reflectance ratio had significantly higher AROC (0.85) than NFL reflectance (0.74) and RPE reflectance (0.57).
Conclusions:
Though both NFL and RPE reflectance decreased in glaucomatous eyes, the NFL/RPE reflectance ratio increased the diagnostic power of reflectance of NFL for glaucoma.
Clinical Trial:
http://www.clinicaltrials.gov NCT01314326
Keywords: imaging/image analysis: clinical • nerve fiber layer • optical properties