Subjective observations made during routine examination of eye movement functions (orthoptic status) reveal that very slow, smooth-pursuit eye movements in cancer patients are irregular. To objectively measure such movements, a video-based system was built to allow analysis of very slow, smooth-pursuit eye movements (1.8 degrees /s). Analysis involves quantification of drift and jerk-like gaze movements that cause deviations in gaze direction from the predicted trajectory. Gaze deviations observed in cancer patients are compared to those for the normal population. Our results show that deviations are more important in cancer patients than in the normal population. The difference is statistically significant (p<0.05) for deviations ranging between 0.75 degrees and 1.75 degrees . In the future, the system may possibly be used in the diagnosis of cancer.