Protan response times to red lights in a mildly hypoxic environment.

Purpose: This study was conducted to determine whether protans have slower reaction times to red lights than individuals with normal color vision and to identify whether protan reaction times increase differentially in a mildly hypoxic environment.

Methods: Simple reaction times (SRT) to a red light-emitting diode (LED) display were measured using the Psychomotor Vigilance Task (PVT) at ground (1293 ft/394 m), simulated 12,400-ft (3780-m) altitude, and 20 min after returning to ground. Subjects were 13 individuals with normal color vision (NCV), 12 with a deutan color vision defect, and 4 with a protan color vision defect.

Results: The mean reaction times increased by 8% with altitude and decreased after returning to ground for all groups. However, the reaction times of the protans were often faster than the NCV mean and never below the NCV 10(th) percentile. The only significant difference between color vision groups was the slowest mean reaction time of the NCV group was slower than both the pooled dichromats and pooled anomalous trichromats across all conditions by 23%. The number of lapses did not vary with altitude, but the dichromatic subjects had significantly fewer lapses than the trichromatic subjects across all conditions.

Conclusion: Although protans may be slower to respond to some red warning lights, this decrement in performance could not be demonstrated under the conditions of our experiment. Furthermore, the protan group's simple reaction times were not differentially affected by mild hypoxia. These results suggest that the red LEDs were sufficiently bright for these protan observers.