The impact of stress on visual function in nystagmus

• Main Author: Jones, Philip Hugh
• Published: Cardiff University 2011
• Subjects: 617.7; RE Ophthalmology
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.567164

Infantile Nystagmus Syndrome (INS) is defined as a constant involuntary movement of the eyes, affecting 0.12% of the population. Previous research shows that eye movements in patients with nystagmus increase in stressful conditions, and they report that their vision gets worse. However, there have been no definitive conclusions as to the effect of stress on visual acuity (VA). The aim of the studies described here was to assess visual function, including VA, during periods of stress. The results showed that there was no difference in VA measured with horizontally and vertically oriented Landolt C’s, but, in agreement with published research, VA was found to be poorer when using vertically oriented gratings as compared to horizontal gratings. Using a Trans-Cutaneous Electrical Nerve Stimulation (TENS) machine, an effective clinical stressor, we confirmed that the intensity of nystagmus increased when under stress; however VA, as measured using Landolt Cs, was not affected. Patient response time also increased during stressful periods and was significantly longer in INS than in control subjects. Using a questionnaire, we identified the most stressful situations for patients with nystagmus as being: “finding a person in a crowd” and “crossing a road in heavy traffic”. Under stress, rather than vision becoming blurred, patients with nystagmus reported that they “take longer to see things” and “have difficulty with seeing facial features and small detail”. The results reported here have important implications for patients with nystagmus in the real world, strongly suggesting that, although maximum acuity is unaffected by stress, more time should be allowed for tasks at both work and school. Further research is required to fully understand the changes in other aspects of visual function with stress.