This study was conducted to determine abnormalities of the GDx Glaucoma Scanning System parameters in patients with tilted discs, in order to set guidelines for the evaluation of glaucomatous damage in this situation. The objective was to determine which GDx parameters displayed the highest level of variation, and which remained unchanged in tilted disc syndrome. RNFA was polarimetrically conducted on 45 eyes from 26 subjects with tilted discs, and 43 normal eyes with Nerve Fiber Analyzer II (Laser Diagnostic Technologies). All parameters except inferior maximum, average thickness, ellipse average, and inferior average displayed a significant difference between the two groups (p < 0.05). Although NFA is useful in glaucoma diagnosis, the majority of the GDx parameters, as shown in our study, are unreliable in tilted disc syndrome in this respect.