Study of visual acuity and reaction time at different contrast levels with a bright background for army aviation candidates

Objective To investigate the visual acuity and reaction time at different contrast levels with a bright background for selecting aviation cadets and to evaluate the significance of different contrasts on visual acuity measurements in the selection of personnel for a career requiring special skills. Methods One thousand sixty-two students (2124 eyes) with normal visual acuity who had been selected as aviation cadets in Shanxi province and Gansu province during 2007-09 to 2007-10 were enrolled. logMAR visual acuity and reaction time were measured at four contrast levels (100%,25%,10%,5%) with a bright background in dark room with a multi-functional visual acuity tester (MFVA-100). A pairedsamples t-test and linear regression analysis were used to analyze the data with SPSS 11.0 statistics software. Results Visual acuity decreased gradually with a decrease in the contrast level. Visual acuity at low contrast was significantly worse than that at high contrast (P0.01). The visual acuity at 100% contrast was linearly related to that of any other contrast level (P0.01). Fluctuating differences in visual acuity and reaction times increased with a decrease in contrast level. Conclusion It is beneficial to adopt a contrast sensitivity test as a supplement to visual acuity examinations in the selection of aviation cadets. The results can provide information to assist in the selection of personnel for some careers requiring special skills.