Photostress recovery time among commercial drivers in Nigeria

Abstract

Photostress recovery time (PSRT) test is a simple technique used to assess the macular function. Prolonged recovery time is attributed to the delay in regeneration of visual pigments after being bleached with a bright light.  In car drivers with macular degeneration, photostress effects from opposing cars may bleach retinal pigments and cause a dramatic drop in visual acuity.

The study aims todetermine the prevalence of abnormal PSRT and the association of PSRT with age, visual function and driving safety among commercial drivers in Nigeria.A cross-sectional descriptive study was carried out in Ilorin metropolis, a city in north central Nigeria.Of the estimated 4,729 registered commercial drivers, 327were selected using multistage sampling methods. Structured questionnaire was administered by trained research assistants. PSRT test and visual function tests were carried out by the principal researcher and an assistant.

Subject with normal healthy macular function should be able to read the visual acuity line just above the pre-exposure visual acuity line in 50-60 seconds. Patients with a macular problem may have recovery times lasting 1.5 to 3 min or longer. The study revealed a statistically significant association between PSRT and visual acuity as well as colour vision (p<0.05). No association existed between PSRT and age, visual field and driving safety. Majority of the respondents with normal PSRT had fair driving safety.

Regular visual screening especially during license renewals may be the most useful tool for the detection of impaired visual function and delayed photo stress recovery time among commercial drivers.

Keywords:  Photostress, Macular degeneration, Commercial drivers