Assessment of Optic Nerve Head Pallor in Primary Open-Angle Glaucoma Patients and Healthy Subjects

Purpose: To investigate optic nerve head (ONH) pallor quantitatively in patients with primary open-angle glaucoma (POAG) and in healthy subjects, and to examine the relationship to mean deviation in perimetry (MD), cup-disk ratio (CDR), and diameters of retinal vessels. Methods: A total of 89 POAG patients (67.6 +/- 11.1 years) and 48 healthy subjects (63.3 +/- 14 years) were included. A dual-bandpass transmission filter was introduced in the illumination path of the fundus camera of the Dynamic Vessel Analyzer (Imedos Systems UG) and two monochromatic images at different wavelenghts (548 +/- 10 and 610 +/- 10 nm) were recorded simultaneously. ONH pallor was defined as the quotient of light reflection in both spectral channels. Pallor values were averaged over four fields which were positioned on the ONH. The mean of these measurements was calculated. In 47 of 89 POAG patients diameters of retinal vessels were determined peripapillary. Results: In POAG, the ONH showed a significantly higher pallor value compared to healthy subjects (82.34 +/- 19.28 vs. 62.67 +/- 10.41, p < 0.001). ONH pallor was correlated to indicators used to estimate disease severity: MD (r = -0.565, p < 0.001) and CDR (r = 0.561, p < 0.001). The pallor value was associated to diameters of retinal arterioles (r = -0.313, p = 0.032) and venules (r = -0.397, p = 0.006). Conclusions: Pallor determined by this method was higher in POAG patients than in healthy subjects and increased in patients with advanced disease. ONH pallor might result from a reduced blood perfusion of the ONH or tissue atrophy accompanied by vessel obliteration in POAG. By measuring ONH pallor additional diagnostic information about the vitality of the neuroretinal rim might be gained in glaucoma patients.