AIM: To analysis and compare the influence of surround luminance and pupil diameter on neural contrast sensitivity function(NCSF)and contrast sensitivity function(CSF).

METHODS: Ten healthy male volunteers(10 eyes)were recruited in this study, and the right eye was tested in this experiment. Different surround luminance levels and glare were set by Vision Monitor System to measure CSF curves of normal pupil, 3.0mm pupil and 5.0mm pupil. Modulation transfer function(MTF)curves of 3.0mm pupil and 5.0mm pupil were measured by Optical Quality Analysis System. NCSF was the ratio of CSF and MTF.

RESULTS:NCSF and CSF curves went downward considerably and the curve waves shifted towards low spatial frequency as the surround luminance decreases. Compared with NCSF, the curve waves of CSF shifted towards lower spatial frequency. The change of CSF was affected by NCSF and MTF. When pupil diameter increases, MTF curve went downward. While the NCSF and CSF curves mounted up at low spatial frequency in the mesopic and photopic visual environment and showed downward trend at high spatial frequency in excessive bright environment or with glare. In the scotopic visual environment, the slight pupil diameter change cannot considerably affect CSF and NCSF curves.

CONCLUSION:CSF is influenced by MTF and NCSF which reflects the function of the retina-brain neural system. The curve shape of CSF is similar to NCSF, but the curve wave is at lower spatial frequency. NCSF and CSF curves go downward as the surround luminance decreases. As the pupil diameter increases, NCSF and CSF curves mount up at low spatial frequency but show downward trend at high spatial frequency in excessive bright environment or with glare.