The effect of pupil dilation with tropicamide on vision and driving simulator performance.

PURPOSE: To assess the effect of pupil dilation on vision and driving ability. METHODS: A series of tests on various parameters of visual function and driving simulator performance were performed on 12 healthy drivers, before and after pupil dilation using guttae tropicamide 1%. A driving simulator (Transport Research Laboratory) was used to measure reaction time (RT), speed maintenance and steering accuracy. Tests of basic visual function included high- and low-contrast visual acuity (HCVA and LCVA), Pelli-Robson contrast threshold (CT) and Goldmann perimetry (FIELDS). Useful Field of View (UFOV--a test of visual attention) was also undertaken. The mean differences in the pre- and post-dilatation measurements were tested for statistical significance at the 95% level using one-tail paired t-tests. RESULTS: Pupillary dilation resulted in a statistically significant deterioration in CT and HCVA only. Five of 12 drivers also exhibited deterioration in LCVA, CT and RT. Little evidence emerged for deterioration in FIELDS and UFOV. Also, 7 of 12 drivers appeared to adjust their driving behaviour by reducing their speed on the driving simulator, leading to improved steering accuracy. CONCLUSIONS: Pupillary dilation may lead to a decrease in vision and daylight driving performance in young people. A larger study, including a broader spectrum of subjects, is warranted before guidelines can be recommended.

Effectiveness of occlusion therapy in ametropic amblyopia: a pilot study.

AIMS/BACKGROUND: To examine the relative contributions of non-specific (for example, spectacle correction) and specific (that is, occlusion therapy) treatment effects on children with ametropic amblyopia. To assess the importance and practicality of objectively confirming the prescribed occlusion dose. METHODS: Subjects were entered into a two phase trial. In the first ('pretreatment') subjects were provided with spectacle correction and underwent repeat visual acuity (VA) and contrast sensitivity (CS) testing until acuity in their amblyopic eye had stabilised. Subjects then progressed to the second phase ('treatment') in which they underwent direct, unilateral occlusion for 1 hour per day for 4 weeks. Patching was objectively monitored using an occlusion dose monitor. RESULTS: Eight subjects completed the trial, all but one of whom achieved > 80% concordance with the occlusion regimen. Within the pretreatment phase, mean amblyopic eye VA improved by 0.19 log units (p = 0.008) while mean CS gained 0.09 log units (p = 0.01). An identical improvement in mean VA was recorded in the fellow eyes (p = 0.03) while mean CS gained 0.11 log units (p = 0.02). Within the treatment phase, mean VA further improved (0.12 log units, p = 0.009) although this gain had halved by the end of treatment and was no longer statistically significant (p = 0.09). CONCLUSIONS: Visual performance improved significantly during pretreatment whereas further gains seen during occlusion were not sustained. Evaluation of occlusion regimens must take into consideration the potentially confounding influence of 'pretreatment effects' and the necessity to confirm objectively the occlusion dose a child receives.