NGF and iNOS Changes in Tears from Video Display Terminal Workers

Purpose: To investigate Nerve Growth Factor (NGF) and nitric oxide synthase (iNOS) levels in tears obtained from Video Display Terminal (VDT) workers and correlate their expression with ocular signs and symptoms.Methods: A total of 120 VDT workers (62M/58F; 31-63years old) and 40 age/sex matched no-VDT volunteers (19M/21F; 30-60years old) were enrolled in the study. Participants completed the OSDI questionnaire and were subjected to clinical assessment of ocular surface status, including ocular symptoms and tear film parameters. NGF and iNOS levels were quantified in tear samples and their expressions correlated with OSDI, ocular symptoms and tear film parameters.Results: 59.17% of the studied population was symptomatic based on OSDI scores. Women were more commonly affected. The most frequent symptom was asthenopia and except for dryness, no differences were found between genders regarding other symptoms. A statistically significant decrease in NGF levels was found between normal and moderate (p<0.05) and between mild and moderate (p<0.05) OSDI grading. iNOS expression was increased in moderate OSDI grading compared to normals (p<0.05). A negative correlation was found between NGF and respectively OSDI results, dryness and blurry vision (p<0.05). No correlations were found among NGF, iNOS and ocular surface parameters (Schirmer, BUT, ocular surface staining).Conclusion: Our data suggest that NGF and iNOS levels contribute to VDT ocular discomfort. Further studies are required to better understand the relationship between NGF and iNOS in VDT ocular surface.