Objective    To observe the thickness of retinal nerve fiber layer (RNFL) at the circle around optical nerve with a scanning area of 3.0 mm or 3.46 mm at diameter using optical coherence tomography (OCT) in normal subjects and evaluate the difference between them and its clinical meanings.     Methods    Zeiss OCT 3000 was used in 112 eyes of 98 normal subjects in our hospital to measure RNFL thickness with circle scan (diameter

3.0 mm and 3.46 mm) around optical nerve. All data were analyzed in the program of RNFL THICKNESS AVERAGE.     Results    There were no obvious difference among normal subjects at different ages(P>0.05).Significant difference was seen in the thickness of RNFL at different scanning diameters(P<0.01).No significant difference was seen between the superior and the inferior

but significance was observed between the nasal and the temporal.     Conclusion    OCT measuring RNFL thickness in normal subjects has good reproducibility and it can provide the evidence for clinical diagnosis according to the different RNFL thickness with different scanning diameter.