Spectral-domain OCT is an established tool to assist clinicians in detecting glaucoma and monitor disease progression. The widespread use of this imaging modality is due, at least in part, to continuous hardware and software advancements. However, recent evidence indicates that OCT scan artifacts are frequently encountered in clinical practice. Poor image quality invariably challenges the interpretation of test results, with potential implications for the care of glaucoma patients. Therefore, adequate knowledge of various imaging artifacts is necessary. In this work, we describe several factors affecting Cirrus HD-OCT optic disc scan quality and their effects on measurement variability.