BACKGROUND/OBJECTIVES: Glaucoma can impact the ability to perform daily life activities such as driving. In such tasks, reaction time is critical to detect hazards. Understanding the modalities that affect response times is thus essential for clinical care. SUBJECTS/METHOD: Simple reaction time tasks, in which participants respond as fast as possible to a stimulus, constitute a basic measure of processing speed. Simple reaction times to visual and auditory stimuli were compared to assess whether glaucomatous patients exhibit a general slowing in execution speed or a specific slowing in response to visual signals.Twenty participants with primary open angle glaucoma, 16 age-matched normally sighted controls and 16 young controls were instructed to press the space bar of the computer as soon as they detected a visual (a 3° black ring) or an auditory (a 440 Hz sound) signal. The two modalities were tested in independent blocks of 63 trials. RESULTS: Participants with glaucoma were significantly slower than young and older controls in the visual modality but not in the auditory modality, in which simple reaction times did not differ significantly between groups. CONCLUSION: This study suggests that the reduced processing speed in glaucoma cannot be attributed to motor or attentional impairments and probably results from a delay in the transmission of visual information.