Visual acuity, color vision, and visual search performance at sea

Area of Science:

• Maritime safety
• Human factors in search and rescue
• Ophthalmology

Background:

• Effective search and rescue (SAR) at sea relies on visual capabilities of watchkeepers.
• Assessing the impact of visual acuity and color vision on SAR performance is crucial for optimizing operational efficiency.

Purpose of the Study:

• To evaluate the correlation between visual acuity, color vision, and the performance of watchkeepers during a simulated maritime search and rescue exercise.
• To determine the potential efficiency gains from implementing selective screening for visual acuity and color vision.

Main Methods:

• Fifty-seven watchkeepers participated in a sea-based SAR exercise, searching for life rafts under various conditions (daylight, night with night vision goggles).
• Visual acuity and color vision tests (Dvorine pseudoisochromatic plates, Farnsworth color test) were administered.
• Environmental factors (wind, waves, weather) were recorded as covariates.

Main Results:

• Daytime detection performance positively correlated with low-contrast visual acuity and negatively with color vision test errors.
• Watchkeeper performance was superior during the initial 30 minutes of a one-hour watch.
• No significant relationship was found between visual acuity or color vision and life raft detection using night vision goggles.

Conclusions:

• Visual acuity and color vision are critical for effective daylight maritime search and rescue.
• Implementing selective screening for visual acuity (12% improvement) and color vision (10% improvement) could significantly enhance daylight search performance.
• Night vision goggle performance in SAR is not directly correlated with standard visual acuity or color vision tests.