LED Railway Signal Detection Rather Than Recognition is Affected by Both Refractive and Non-refractive Blur

Area of Science:

• Ophthalmology
• Vision Science
• Occupational Health

Background:

• Refractive defocus impacts red signal identification.
• Railway safety workers require accurate signal perception.

Purpose of the Study:

• Investigate refractive and non-refractive defocus effects on rail signal perception.
• Utilize the Railway LED Lantern Test (RLLT) for simulated practical assessment.

Main Methods:

• Recruited 20 healthy adults (19-59 years) with best corrected visual acuity (BVCA) ≥ 6/9.
• Assessed participants using the RLLT under five conditions: best corrected, +0.50 DS, +0.75 DS, and Bangerter filters 1.0 and 0.8.
• Excluded subjects with active ocular conditions.

Main Results:

• Red signal errors were significantly more frequent than yellow or green errors (p < 0.0001).
• Bangerter filters induced more errors than refractive blur (p < 0.0001).
• Failing to see red signals was the predominant error, more frequent with Bangerter filters than refractive blur (p < 0.0001).

Conclusions:

• A significant proportion of rail signal perception errors stem from not seeing the red signal.
• Non-refractive blur, simulated by Bangerter filters, increases color errors more than refractive blur.