Relationship between contrast sensitivity and stereopsis among commercial motor vehicle drivers' in Benin City Metropolis, Edo State, Nigeria

Purpose: Contrast sensitivity (CS) and stereopsis play significant roles in discerning variation in brightness between a figure and its background, including judging accurately the location of objects in the visual space. The purpose of this research was to ascertain the relationship between contrast sensitivity and stereopsis impairment among drivers of commercial motor-vehicles in the city of Benin, Edo State, Nigeria. Methods: A cross-sectional survey of 341 commercial motor-vehicle drivers aged 20 - 70 years with mean age of 48.09 years ± 11.21 standard deviation in Benin City Metropolis using a purposive random sampling technique was conducted. Data were obtained using adjusted National Eye Institute Vision Function Questionnaire. Pelli-Robson test was done to assess contrast sensitivity. Stereopsis was examined with TNO Random Dot Stereogram Chart. Data was analysed with version 29.0 of IBM-SPSS using Chisquare test and Pearson coefficient of correlation, and reported in tables and chart. Significance level was considered at Probability value < 0.05. Results: 341 commercial drivers that comprised 326 (95.6%) males and 15 (4.4%) females were recruited for the study. The prevalence of impaired contrast sensitivity was 21.7%. Prevalence of impaired gross and fine stereopsis was 18.8% and 83.9% respectively. There was a significant interrelationship linking contrast sensitivity with gross stereopsis (r = 0.202; P <0.01) and fine stereopsis (r = 0. 135; P <0.05). Conclusion: This study demonstrated that stereopsis decreased with decrease in contrast sensitivity. Routine contrast sensitivity and stereopsis assessment of drivers are recommended prior to issuance of drivers’ license and re- license.