Poorer Visual Acuity and Visual Field Leads to More Collisions Per Mile in Bioptic Drivers

Bioptic drivers with worse visual acuity and visual field drive less than other bioptic drivers and have more collisions per mile. However, their per mile collision rate was similar to that of their fully sighted peers before accounting for age distribution, according to research published in Optometry and Vision Science.

Researchers enrolled 73 participants who drove using bioptic telescopes in a study (mean age 51±16 years, 25 women). The cohort had a mean bioptic driving experience time of 11±6 years and causes of low vision included albinism, retinal dystrophy affecting the macula, and age-related macular degeneration (AMD) (18%, 28%, and 5%, respectively). Researchers gathered data from the Ohio Bureau of Motor Vehicles database, obtained records from clinical visits, administered the Driving Habits Questionnaire, and asked participants to estimate the total mileage they had driven over the course of 1 year.

Drivers reported driving a mean 9746 annual miles (median 7000).

After adjusting for age, the investigators noted visual acuity, contrast sensitivity, and total horizontal visual field were associated with self-reported annual mileage (P =.02, P =.01, and P =.02, respectively). 

A total of 42 drivers with at least 1 documented collision after bioptic licensure were involved in 95 reported collisions (66% no injuries, 15% possible injury, 9% non incapacitating injury, and 10% unknown injuries) across 8.5 million miles (11.2 collisions per million miles). Mean annual collision rate was 0.14.

Regression models revealed that drivers with worse visual acuity ( rate ratio, 4.08; 95% CI, 1.29-12.94; P =.02) and less horizontal visual field (rate ratio, 0.980; 95% CI, 0.967-0.994; P =.005) experienced a higher per-mile collision rate. Although reduced contrast sensitivity resulted in less driving exposure among bioptic drivers, it was not associated with per-mile collision rate (rate ratio, 0.57; 95% CI, 0.24-1.33; P =.19).

Researchers assert that reduced visual acuity and visual field should not be the only factors to evaluate when analyzing per-mile collisions caused by bioptic drivers. They remind us that “consideration of driving exposure may be especially important when studying bioptic drivers because they may have different driving habits than would typical comparison groups” 

Limitations of the study include a small sample size, reliance on self-reporting for mileage data, and the inclusion of motor vehicle data from only 1 US state. 

Reference

Zhou AM, Flom RE, Raasch TW, Segerstrom EE, Dougherty BE. Vision, driving exposure, and collisions in bioptic drivers. Optom Vis Sci. 2022;99(2):121-126. doi:10.1097/OPX.0000000000001836