P10: The variation of nitrite content in human tear under visual fatigue

Abstract

Modern society has made a lot of demands for long hours of visual task performance, such as reading novels in mobile phone, viewing motion images on TV, editing documents on computer, etc. These demands easily lead to visual fatigue. How to assess visual fatigue? There is no, to our knowledge, an effective method. In this paper we studied the variation of nitrite content in human tear under visual fatigue, in order to find a method to assess visual fatigue. 20 Healthy non myopia volunteers (aged 20–25 years, 10 males and 10 females) took part in the study. The tear of volunteers suffered visual fatigue by reading in inadequate lighting or editing documents on computer was collected by cotton. And then the nitrite content in tear was measured by spectrophotometer assay based on Greiss reaction (Green et al., 1982). When the volunteers read newspaper in the environment of 30 lux, 200 lux and 40,000 lux light intensity for 2 h, the nitrite content in tear were 78.2 μmol/L, 61.3 μmol/L and 112.1 μmol/L respectively,and the order of eye ache and eye bulge was 40,000 lux >30 lux >200 lux. However, when the volunteers just sat in this environment, the nitrite content were 43.5 μmol/L, 40.1 μmol/L and 50.3 μmol/L respectively, and there is no significant subjective symptoms of eye ache and eye bulge except 40,000 lux in which the participants feel a little eye bulge. It was clear that reading increased the content of nitrite in tear which was positive correlation with the subjective symptom of visual fatigue. When the volunteers editing documents on computer for 2 h, they also feel eye ache and eye bulge. And the nitrite content in tear was 75.6 μmol/L which was 189 % of that in tear before editing. Long hours reading or editing documents on computer increased nitrite content in tear which was positive correlation with the subjective symptom of visual fatigue. Therefore the nitrite content in tear can be taken as a marker of assessing visual fatigue. This work was supported by the Foundation of Tianjin developing marine economy by science and technology (KJXH2012-14).