CONCLUSION: These data suggest that visual acuity during quiet sitting is dynamic, requiring full body interaction of vestibulo-ocular and postural responses. These findings may have practical implications for seating design and design of tasks requiring good visual acuity while seated. OBJECTIVES: Looking at something during quiet sitting is usually assumed to be a static activity. We tested the idea that visual acuity during quiet sitting is dynamic, requiring integration of whole body responses as well as intact vestibulo-ocular reflexes. MATERIALS AND METHODS: Normal subjects and patients scheduled for acoustic neuroma resection were tested preoperatively. Patients were then tested during the four in-patient postoperative days. Testing was done while seated, with or without head and back support, while reading numbers from slides on a laptop computer at eye level, in font sizes from 20 pt to 12 pt. The dependent measure was percent correct per font size. RESULTS: In both groups scores while sitting unsupported were significantly higher than with full support or only back support. In patients, scores were significantly decreased on postoperative day 1 and gradually increased toward normal but maintained the pattern of better scores when sitting unsupported than with head or back support.